What Happens to the Fat We Eat?

(The illustration is a simplification of a figure in the 2007 Encyclopedia Brittanica. If it seems too fuzzy to decipher, click on it to see a clearer version.)

For the low-carber, fat is an important macronutrient. What happens when we eat fat?

One of the important aspects of fat is that it is not water-soluble. In order to begin the digestion process, the liver makes bile, which in collected in the gallbladder and is secreted into the small intestine. The bile acts as a detergent. The bile salts in it have a lipophilic side, which binds to the fat droplets, and a hydrophilic side, which suspends the droplets in the watery mixture of the food we have just eaten.

The triglycerides or fats in the suspended droplets cannot be absorbed by the intestine. To accomplish absorption. the pancreas secretes an enzyme called pancreatic lipase into the small intestine, Pancreatic lipase breaks down each triglyceride molecule into two free fatty acids plus a monoglyceride. "Mono" means one, and in this case it means that one of the fatty acids remains attached to the original glycerol backbone. When the triglyceride is broken down into subunits, it is able to pass into the absorptive cells of the intestinal mucosa. After the three subunits have transited the wall of the intestine, the fatty acids are added back to the glycerol backbone and they form a triglyceride once more.

Inside the cells of the intestine, triglycerides are packaged into chylomicrons. Chylomicrons are large diameter (75-1200 nanometer) particles that contain a bit of protein, a bit of cholesterol and lots of triglycerides. The chylomicrons are not secreted directly into the blood but into the lymphatic system. They eventually arrive at the thoracic duct and then are deposited into the blood at the left subclavian vein. Once they enter the blood, they are transported into capillaries and are able to reach the entire body.

One of the proteins in a chylomicron is called apo C-II. This protein has the ability to activate an enzyme called lipoprotein lipase or LPL. Lipoprotein lipase resides on the capillary walls of tissues that have a high requirement for triglycerides, such as cardiac muscle cells, skeletal muscle cells and fat (adipose) cells. The activated lipoprotein lipase acts on the triglyceride molecules (called triacylglycerols in the illustration above) stored inside the chylomicron. It hydrolyzes or breaks down the triglycerides into two fatty acids plus a monoglyceride. Just as we saw in the intestine, intact triglycerides cannot pass through the cell walls, but when they are hydrolyzed into subunits, they can be absorbed into the cells. Once inside, they can be used for energy in the muscle cells or reassembled into triglycerides and stored in the adipose cells.

When we eat a piece of bacon, we start with fat and end with fat (or for the low-carber--energy from the fat). But, as you can see, there are may steps involved in getting from the beginning of the process to the end.

What Is Fat?

Low-carbers spend lots of their time thinking about fat, both in terms of the excess girth on their bellies and hips, and as an important macronutrient. Although fat is a perfectly natural substance, it may surprise you to know that fat is a chemical.


In chemical terms, fats are referred to as triglycerides. They are composed of two types of subunits. The first subunit, glycerol, is shown above. Although the glycerol portion is not the most important subunit of a fat, it is the root of its chemical name, triGLYCERide. Glycerol has a three-carbon backbone, depicted by the vertical line of C's in the figure above. The active groups in glycerol are the -OH or hydroxyl groups.

The other subunits are called fatty acids. There are three of them in each fat molecule; hence the prefix TRIglyceride. In the example above, each fatty acid contains a chain of carbons represented by a horizontal row of nine C's. In real life, the length of the chains can be from four C's to twenty eight C's. The chains do not have to be the same length within the triglyceride--any assortment is possible. The active group in the fatty acids is known as a carboxylic acid and is also shown above.

The active groups of the three fatty acids are joined to the active groups of the glycerol backbone though a process called esterification. For those who are interested in the enzymatic reactions involved, they are described here. At any rate, three fatty acids attached to one glycerol backbone produces a TRI-GLYCER-ide, a triglyceride, which is one molecule of fat.

That's probably enough biochemistry for this time. There will be more fascinating facts about fats in later posts. :-)

Be Encouraged!

As most of my readers know, low-carbing is a lifestyle, not a quick weight-loss diet. Early in the process of low-carbing, weight is often lost rapidly, and some of the health improvements come right away. But as weeks move into months move into years, changes come more slowly and more gradually. Reading a diary or meeting an old friend will be a reminder that the low-carb life is better, but day-to-day excitement gradually morphs into an overall feeling of wellbeing.

As low-carbing becomes a way of life, what used to be a black-and-white eating plan begins to become shades of gray. What about eating a slice of Smart Carb bread instead of using a lettuce wrap on my sandwich? I miss bread, and this bread even contains exta (incomplete) protein. Could I substitute one or two low-carb Monster Energy drinks for a couple of bottles of water? They sure taste good and give me a mental and physical boost after all.

There are all sorts of low-carb substitutes for high carb foods. There are many vendors ready to sell them to us, and lots of cookbooks to show us how to make them ourselves. We see low-carb forums with large areas devoted to recipes. And if we try low-carb substitutes, in the short term it very often does not hurt. But what happens in the long term?

In April 2009 there was a Nutrition & Metabolism Society conference in Charleston, South Carolina. Jimmy Moore attended and posted pictures of some prominent low-carbers on his menus blog. Please check out the pictures of low-carb experts Laura Dolson and Dr. Mary Vernon. Another low-carb expert, Dana Carpender, also seems to be having weight issues. Jimmy Moore himself has recently reported that he weighs 246 pounds (an obese-level BMI of 30.7) with a body fat percentage (measured on a bathroom scale) of 31.5.

How could this be? These are prominent low-carbers. Please click on and scroll through the websites of Laura Dolson, Dr. Mary Vernon--note the array of fruit across the top, Dana Carpender and Jimmy Moore's menus blog for a clue.

Does this mean that low-carbers are doomed--doomed to gain weight in the long run? No. It does mean that the basic low-carb formula of complete protein, healthy fat and a few low-carb vegetables is hard to maintain over time. Dr. Michael Eades recently had a blogpost that graphically demonstrated that two groups of people living under similar circumstances could have drastically different outcomes for health and longevity. The hunter-gatherers had periods of starvation and fairly short lifespans, but were healthy in most respects. The agriculturalists had access to the same array of animal proteins, but they preferred to eat carbs. They were willing to suffer from increased infant mortality, painful defects in bone formation, dental cavities and bone infections in order to get a high percentage of calories from carbs rather than animal sources.

The pull of carbs and carb-replacements is strong. For one thing, they taste good. For another, the culture we live in encourages high-carb eating. But for those who are hanging in there and eating complete protein, healthy fat and low-carb vegetables, keep up the good work! In the long run, you're doing what is best for your body and in the long run, you will reap the rewards.

Not All Proteins Are Created Equal

In the previous post we learned that eating 30 grams of protein per meal can increase fat loss, preserve lean muscle, prevent osteoporosis and improve the symptoms of type 2 diabetes. But protein can come from many different sources, including meat, eggs, dairy products and plants. Does the source of dietary protein make any difference?

In a word--yes. Proteins are linear molecules made of building blocks called amino acids. Proteins are synthesized within cells by an organelle called a ribosome that reads the "recipe" for each particular protein from another linear molecule called RNA. As the ribosome reads the RNA, it looks in its immediate vicinity for whichever of the twenty different amino acids is called for next in the sequence. If the ribosome comes to a point in the RNA "recipe" where the corresponding amino acid cannot be found, the ribosome falls off the RNA and synthesis of the protein stops. Until there is enough of the missing amino acid, that specific protein cannot be made.

Where does the missing amino acid come from? Some amino acids like alanine, glutamate and asparagine, can be made by our bodies. Unless there is an inborn error of metabolism, these amino acids are present in abundance. However, other amino acids like lysine, methionine and tryptophan cannot be made by the human body. These are called essential amino acids and they must be consumed as part of the diet. If any essential amino acid is not consumed in sufficient quantity, its absence shuts down much of the body's protein-synthesis machinery.

Cereal grains such as corn, millet, rice and wheat are typically low in the amino acid lysine. Even though a person consumes many grams of protein in the form of cereal grains, the low abundance of lysine will prevent his or her body from making many of the proteins it needs for growth and repair. Legumes such as beans and peanuts are low in the amino acid methionine. Eating lots of beans or peanuts will provide lots of protein, but when the plant protein is broken down into its amino acids and these are then used for human protein synthesis by ribosomes, the ribosomes will be unable to find enough methionine to produce the proteins the body needs to sustain itself. When a food source is deficient in one or more essential amino acids, it is said to contain incomplete protein. Incomplete protein can be used as a source of calories or energy, but it is inefficent in meeting the body's need for human protein synthesis.

It is possible to mix plant sources of protein such as corn and beans in order to obtain a better overall amino acid profile. However, the complementary sources must be consumed within several hours of each other or the beneficial effect will be lost. The complementarity must also be well-understood. For instance, almonds are low in lysine and methionine, so addition of cereal grains or legumes to almond protein will still result in poor protein nutrition. Another aspect to consider is the fact that plant sources of protein are often more difficult to digest than proteins found in animal sources such as whey, meat or eggs. If the plant products are refined, digestibility is improved, but nutritional quality is lost.

Animal sources of proteins typically have a much better balance of essential amino acids than plants do. When you think about it, that makes sense. Plants do not use their proteins to make blood, muscles or organs. Plant proteins are used for different funtions, and the amino acid profiles of those proteins are unique. On the other hand, animals are similar to people in many ways, and their proteins require about the same percentage of amino acids that are required to make proteins having similar functions in humans. Good sources of animal protein include whey protein, casein (cheese), eggs, meat and fish. An interesting comparison of protein quality can be found here. As the chart in that link indicates, plant protein from soy does provide a complete array of amino acids. However, because consumption of soy products may be associated with alterations in hormone levels, they should be used with caution.

Protein is an important macronutrient. It has many beneficial primary and secondary effects, but if the protein consumed is not of high quality, i.e., if it is not complete protein, the body will not be able to use it effectively to make and repair skin, nails, hair, bone and muscle.

It's What's for Breakfast, Lunch and Dinner

Normally the topics of discussion in this blog center around carbohydrates. But for something completely different, this time we'll discuss another macronutrient--protein. Recently Donald Layman published an article in Nutrition & Metabolism entitled Dietary Guidelines Should Reflect New Understandings about Adult Protein Needs. His findings are so interesting that I've decided to summarize them here. Links that back up each point can be found in the list of references at the end of his article.

Layman begins by discussing the fact that protein has traditionally been thought of as an expensive nutrient. While that's true in the context of managing animals in a feedlot, it is a little less true in a human society where families are willing to pay $5.00 for a box of breakfast cereal. Nevertheless, because we have been conditioned to think in terms of eating small amounts of protein, it is important to establish how much protein is enough.

The Institute of Medicine, Food and Nutrition Board, has established a recommended daily allowance (RDA) between 0.36 grams and 1.1 grams of protein per pound of total body weight. The important aspect of the protein RDA is that it is proportional to current body weight. It is not a percentage of daily caloric intake. In other words, a man who weighs 200 pounds needs to eat a minimum of 72 grams of protein daily. It doesn't matter if his typical caloric intake is 3000 calories per day or if he is dieting and eats only 1000 calories per day. Regardless of his total caloric intake, he should be careful to consume at least 72 grams of protein every day.

Layman points out that the Nutrition Board has not identified an upper risk limit for the amount of protein a person can consume in a day. In other words, a normally healthy person should be able to eat as much protein as he or she wants to. With that in mind, let's take a look at some of Layman's observations in this article.

1. Protein provides a greater satiety value than fats or carbohydrates and reduces food intake at subsequent meals. This effect is seen when protein intake is over 30 grams at a meal, is strongest when the protein is consumed at breakfast and is weakest when it is consumed in the evening.

2. Compared with high-carbohydrate/low-fat/low-protein diets, weight loss diets with higher protein increase thermogenesis and increase the rate of fat loss. When combined with exercise, weight loss diets that are rich in protein can reduce lean tissue loss from 35% to less than 15% and protect from bone loss as well.

3. In children and young adults, skeletal muscle synthesis is regulated by insulin secretion and caloric intake. However, in older adults, this switches to a pathway regulated by the essential amino acid leucine. To protect themselves from age-related loss of lean muscle, it is important for older adults to eat more than 30 grams of protein at least two or three times a day.

4. Exercise, calcium supplements and vitamin D are important for the prevention of osteoporosis. However, in the elderly, it has been found that calcium supplements will not be effective against osteoporosis unless the daily protein intake is greater than 0.55 grams per pound of total body weight.

5. In type 2 diabetics, replacement of dietary carbohydrates with protein has been observed to decrease hyperglycemia, reduce post-prandial hyperinsulinemia, and improve HbA1c.


As the wise man said...getting old is definitely better than the alternative. But perhaps these recent studies have shown us that the symptoms of aging can be slowed down a bit in people who are willing to eat more protein.

Stargazey's Spouse

Yes. I'm married. I have been for 38 years. (That's not him in the picture, by the way.)

Until six years ago, both Hubby and I were significantly overweight. In 2003 I found the Atkins diet and slowly, gradually, I managed to lose 70 pounds and keep them from coming back.

Hubby paid attention the whole time. He didn't object, but he didn't want to participate either. Besides being overweight, he had type II diabetes and was taking 50 units of LANTUS insulin plus about 20 units of regular insulin every day. His blood sugars were over 180 in the morning and 300-400 in the evening. He had retinal edema and microaneurysms that were requiring more and more frequent laser treatments.

Hubby had high blood pressure, too. Even though he was on eight medications, he would sometimes have to go to the emergency room with pressures of 250/130 or higher.

Then a miracle happened. I started this blog and began discussing with him the articles I was finding about low-carb dieting and metabolic syndrome. Hubby has scientific training, and I printed out some of the relevant articles for him. Both of us began to realize that low-carb eating is not only good for weight loss, but it also causes a significant decline in blood pressure and in the symptoms of type II diabetes as well. (Read the article at the link for more specifics and even more links.)

On August 8, 2008, Hubby began the low-carb lifestyle. He didn't do Atkins induction, and he didn't keep his carbs extremely low, but he did manage to stay well below 100 carbs per day most of the time.

Since then, over eight months have passed. Hubby has never, ever stayed on a diet this long. Here are Hubby's current results.

Hubby has dropped eight pant sizes. He has has lost enough weight that he hasn't had a flare-up of his chronic back pain during the past six months.

Hubby now takes 40 units of LANTUS a day and seldom has to supplement it with regular insulin. He has decreased his Metformin from 1000mg to 500mg twice a day. His blood sugars are 80-100 in the morning and about 180 in the evening. His retinal deterioration is progessing, but it is happening much more slowly than before.

Hubby still takes eight blood pressure medications, but they are now working to keep his blood pressure at about 140/70. He has cut his clonidine in half. His ankles no longer swell in the evenings, and he only needs his pressure stockings for airplane trips.

(For those who are interested, the improvements in blood sugar control happened almost immediately, but the improvements in blood pressure were much more gradual.)

Granted, Hubby's experiences do not constitute a scientific study. But they do bear out the fact that the findings of scientific studies can be experienced by real people in the real world. Low-carbing is not a magic bullet. However, for people suffering from the symptoms of metabolic syndrome, including overweight, insulin resistance and high blood pressure, the low-carb lifestyle is definitely worth serious consideration.

Early Insulin Resistance Predicts Subsequent Risk of Metabolic Syndrome

Insulin resistance and metabolic syndrome are most often thought of in connection with middle age. However, an article in the March 2009 issue of the journal Metabolism shows that these conditions get their start early in life.

A biracial group of 475 girls was studied first at ages 9-10 years and then at ages 18-19 years. In the first stage of the study, the invesigators determined the body mass index (BMI) of each girl. They also determined a score called the HOMA-IR, or homeostatis model assessment of insulin resistance. Insulin resistance can be measured using an oral glucose tolerance test (OGTT), but this requires several hours and numerous blood draws. In the HOMA-IR, the fasting levels of insulin and glucose are determined, multiplied, and converted into a score that correlates well with the insulin resistance determined by more technically-demanding methods. The girls were divided in two ways: (1) according to whether their BMI put them in the bottom, middle or top third of the group with regard to to relative obesity (2) according to whether their HOMA-IR score put them in the bottom, middle or top third with regard to relative insulin resistance.

Nine years later the girls were assessed for five metabolic syndrome risk factors. These included:

• Triglycerides
• High-density lipoprotein cholesterol
• Systolic/diastolic blood pressure
• Waist circumference
• Blood glucose

Each risk factor measurement was converted to a z score, which is a way of expressing the relationship of a specific measurement to the population average and the standard deviation of that particular variable. The five z scores were added for each individual. If the total z score was negative, that meant that the individual had a lower risk of metabolic syndrome. (The more negative the total, the better in this instance.) If the total z score was positive, that meant that the individual had a higher risk of metabolic syndrome.

The results were not surprising. The girls who had the lowest BMI and the lowest insulin resistance at ages 9-10 were found to have the lowest risk of metabolic syndrome at ages 18-19. As initial BMI and insulin resistance scores rose, the subsequent scores for risk of metabolic syndrome also rose. The girls who had the highest BMI and the highest insulin resistance at ages 9-10 had the highest risk of metabolic syndrome at ages 18-19. It appears that childhood obesity and insulin resistance interact to produce a higher risk of metabolic syndrome in early adulthood.

Taking it one step farther, the significance of metabolic syndrome in childhood was underlined by a study recently published in the journal Pediatrics, Metabolic Syndrome in Childhood Predicts Adult Cardiovascular Disease 25 Years Later. In this study, the investigators found that the incidence of cardiovascular disease for their 31 patients with pediatric metabolic syndrome was 19.4%, while the incidence was 1.5% for the subjects without metabolic syndrome as children. If these findings are correct, children with metabolic syndrome are significantly more likely than their peers to experience cardiovascular disease twenty five years later as adults.

The obvious question becomes, what happens to these children if intervention takes place between their pre-teen years and their forties? And what would that intervention be? Would it be pharmacological? Would it involve a change in dietary habits? There is a bias at this blog for at least trying a low-carb eating strategy to lower BMI, reduce insulin resistance, avert childhood metabolic syndrome and prevent the progression to adult cardiovascular disease. Whether or not that approach will be tested in the scientific community remains to be seen.

Reversal of Type 2 Diabetes?

Unfortunately there is still no cure for type 2 diabetes. But a recent study published by Eric Westman's group at Duke University suggests that a diet with less than 20 grams of carbohydrate per day or a low-calorie/low-glycemic index diet could enable some type 2 diabetics to decrease their medication and lower their hemoglobin A1c levels.

Investigators randomized 84 obese type 2 diabetic subjects into a Low-Carb group or a Low-Calorie/Low-Glycemic Index (Low Calorie/Low-GI) group. (Full disclosure: the study was funded by the Robert C. Atkins Foundation.) For a period of 24 weeks the Low-Carb group was instructed to eat an Atkins induction-level diet (less than 20 grams of carbohydrate per day, without caloric restrictions). During the same time the Low Calorie/Low-GI group was instructed to eat a reduced-calorie diet that contained 55% low-glycemic index carbohydrates. In the Low-Calorie/Low-GI group, the target caloric intake was set for each individual to provide 500 calories less than that required for weight maintenance.

Fifty eight percent of the enrollees completed the study. Prior to the study the average food intake was 2128 calories a day, with 245 grams in the form of carbohydrates. During the study, the Low-Carb completers ate a daily average of 1550 calories with 49 grams (13%) of the total coming from carbohydrate. The Low-Calorie/Low-GI completers averaged 1335 calories per day with 149 grams (45%) coming from carbohydrate. While compliance with protocol design was not perfect, the Low-Carb group ate about 16% more calories and about two-thirds fewer carbs than the Low-Calorie/Low-GI group did.

Over the 24 weeks of the study, the Low-Carb group lost an average of 24.4 pounds and the Low-Calorie/Low-GI group lost an average of 15.2 pounds. At the same time, both groups saw significant improvements in fasting glucose, fasting insulin and hemoglobin A1c. It is commonly believed that for type 2 diabetics, weight loss causes a drop in hemoglobin A1c. Interestingly, in this group of subjects there was no correlation at all between the amount of weight loss and the level of hemoglobin A1c. (The corresponding figure can be found here.)

Of the 50 patients who were taking insulin at the start of the study, eight in the Low-Carb group and three in the Low-Calorie/Low-GI group were able to decrease or discontinue their insulin altogether. (Click here for a tabular summary.)

The authors go to some lengths to show that the Low-Carb diet was superior to the Low-Calorie/Low-GI diet in this study. In any case, it appears that type 2 diabetics who are able to adhere to either of these diets in the long term can see a significant improvement in their symptoms and a decrease in the need for injected insulin.

Health Care Sacrifices

Heart disease is increasing in the United States. According to the following graph, hospital discharges for coronary heart disease went from about 1.4 million per year in 1970 to about 2.1 million per year in 2000.

In spite of the increasing incidence of heart disease, the death rate from heart disease is decreasing. According to the figure below, from the New York Times, the one-year heart attack survival rate in Medicare patients went from about 58% in 1986 to just under 70% in 2000. The second graph suggests the reason for this: Medicaid hospital spending doubled during that time period.

Patient survival is good. Increasing Medicare costs is bad. Some people have proposed limits on medical spending as a way to cope with the increased costs. One of these is Tom Daschle, who was recently nominated to be head of the Health and Human Services Department. Mr. Daschle's sudden withdrawal from that nomination was unexpected, and he had already provided much advice about acting quickly to ensure that health care legislation could be enacted without the debate and delay that had caused the 1994 health care overhaul to be abandoned.

In 2008 Mr. Daschle wrote a book called Critical: What We Can Do About the Health-Care Crisis. In it he advocated many of the provisions that have found their way into the 2009 economic stimulus package. These include moving medical record keeping to an electronic format that will be available to a new federal bureaucracy, the National Coordinator of Health Information Technology. This organization has a mandate to reduce costs and "help guide medical decisions at the time and place of care."

Mr. Daschle also recommended the creation of another bureaucracy to be modeled the after United Kingdom's National Institute for Clinical Excellence (NICE). This entity is found in the stimulus package as the Federal Coordinating Council for Comparative Effectiveness Research. It is described in the draft report for the bill as being expected to apply a cost-effectiveness standard to approve or reject treatments using a formula that divides the approximate cost for a treatment by the years the patient is expected to benefit from that treatment. The Council will enforce the standard by evaluating doctors and hospitals based on whether or not they are "meaningful users" of the new system. Translation: as Americans get older, they should expect to receive less medical care.

It is hard to contemplate health care reform built on the principle of denial of care to the elderly. However, Mr. Daschle has said that health care reform will not be pain free. He believes that Americans should be more like Europeans in their ability to accept hopeless diagnoses, to do without experimental treatments and to refrain from expecting too much from the health care system. It may be necessary in such a system to provide health care benefits for younger citizens and then ask citizens to be willing to sacrifice those benefits in their later years.

One hopes that all of this has very little to do with low-carbing. It is still permissible to buy eggs, cheese, meat and fresh vegetables. It is still permissible to avoid refined carbohydrates. As far as the health care system, following a low-carb lifestyle will prevent or lessen the impact of many medical conditions including diabetes, heart disease, gallstones, and dental cavities. And being able to achieve excellent health without resorting to medication and hospitalization is a good thing.

If I'm so fat, why am I always hungry?

Body fat serves a number of purposes. It cushions our organs, it insulates us, and it provides a way to store energy. A normal amount of body fat is about 10-20% for men and 15-25% for women. So far, so good.

But sometimes we get too fat. What then? It seems logical to expect that our appetites would decrease, the extra fat would be burned as energy, and we would return to a normal fat percentage once again. But as millions of overweight people can testify, that is not how it always works. They can eat a meal, leave the table feeling full, and two hours later they will be ravenously hungry. They look down at their rolls of excess body fat and wonder, "Why in the world am I hungry? Why can't I just use some of this fat instead of having to eat again?"

In most cases, the answer is one word. Insulin.

Insulin is a hormone which is secreted by the pancreas whenever we eat carbohydrates or protein. Insulin sends a message to the tissues of the body--store nutrients! It is not practical for us to eat continuously. So we eat discrete meals, use some of that energy immediately, and (in response to the signal from insulin) store the rest for use later. Several hours after a meal is consumed, our insulin levels will normally fall, and this will permit nutrients to come back out of storage until it is time for our next meal.

As people get older, the insulin response system may begin to break down. The pancreas has to secrete more and more insulin in order to store nutrients following a meal. The elevated insulin takes longer and longer to return to normal levels, until it stays somewhat elevated all the time. As insulin levels stay high, it becomes progressively harder for stored nutrients to be released between meals. In other words, energy (mostly in the form of fat) is being stored at mealtime, but the energy in the fat can no longer be released efficiently between meals. The result? If a person has excess fat stores but also has persistently high insulin levels, he will be less and less able to access the energy he has stored, but will be forced to eat frequently to provide his body with the energy it needs. Even though he is fat, because of elevated insulin, he will find that he is always (or almost always) hungry.

Obviously the next question is, if a fat person wants to overcome constant hunger, how does he address his elevated insulin? This post, Reversing Insulin Resistance, shows that simply eating a low-carbohydrate diet significantly reduced insulin levels in a small group of obese type 2 diabetic patients. For a more detailed answer, please see this post. It summarizes the three primary strategies for lowering insulin (eat low-carb, eat moderate protein and wait 5-6 hours between meals) and gives several more suggestions for bringing insulin levels (and hunger signals) back into a normal range.

Fatty Liver--Not Just for Geese Anymore

Foie gras, French for "fat liver," is a delicacy produced by force-feeding ducks or geese with corn meal. However, ducks and geese aren't the only species that can get a fatty liver.

Nonalcoholic fatty liver disease (NAFLD) is a condition that can occur in humans. NAFLD, defined as a liver fat content greater than 5.5%, is found in about one third of the U.S. adult urban population. As shown in the figure below, NAFLD (also called hepatic steatosis) progresses from fat deposits that cause liver enlargement, to fibrosis and the formation of scar tissue, to cirrhosis and the actual destruction of liver cells. It occurs in 45% of adult Hispanics, 33% of adult whites, and 24% of adult blacks.



According to the Mayo Clinic website, as diabetes and obesity increase, the incidence of NAFLD is increasing in both adults and children. Unfortunately there is no standard medical treatment for nonalcoholic fatty liver disease. Although several possible treatments are under investigation, none of them has yet proven effective.

With all of that in mind, there is encouraging news from a pilot study performed at Duke University by Eric Westman's group. Westman and his colleagues studied five obese patients who had been diagnosed with fatty liver disease by liver biopsy. They were instructed to follow a low-carbohydrate diet (less than 20 grams of carbohydrate per day) for six months. At the end of that time the patients were biopsied again and they showed significant reductions in liver fat and liver inflammation.

A recent study in Hepatology by Browning et al. explains why a ketogenic diet might reverse fatty liver disease. The investigators divided a group of 14 weight-loss patients into two groups. For two weeks 7 of the patients followed a calorie-restricted diet and the other 7 patients followed a carbohydrate-restricted diet. The scientists used radioactive tracers and NMR spectroscopy to determine how each group was performing gluconeogenesis in their livers.

They learned that the carbohydrate-restricted group produced more of their glucose from lactic acid and amino acids than did the calorie-restricted group. Not only that, the carbohydrate-restricted group burned their liver fat to provide the energy required to perform gluconeogenesis, while the calorie-restricted group tended to use liver glycogen to fuel gluconeogenesis. The researchers also found that the low-carbohydrate group increased fat burning throughout their entire body.

While these studies do not offer conclusive proof that a low-carbohydrate diet should be used to counteract and possibly reverse nonalcoholic fatty liver disease, the findings are encouraging and will be followed up by Dr. Browning and his associates in their next study.

Sweetness and Light Dopamine

Just the taste of a sweet beverage can result in liking, wanting and sipping of more of the sweet beverage. (Please see the previous blogpost for details.) The liking-wanting-sipping phenomenon happens even when the sweet beverage is not actually consumed, and happens in less than a minute. What causes this reaction to the taste of sweet?

In 1989, L.H. Schneider observed that dopamine receptors in the brain are stimulated when rats are allowed to feed themselves sweet solutions. Since that time, many investigators have noticed a relationship between either the taste of sweet or the actual consumption of sweet and the response of dopamine receptors in the brain, both in rats and in humans.

Dopamine is a neurotransmitter found in the midbrain. It has many functions, but one of them is the ability to produce prolonged feelings of pleasure. Increased dopamine signaling is involved in the mechanism of addiction to cocaine, amphetamines, and nicotine. At a more moderate level, novel foods, sweet foods, and overeating also cause increases in brain dopamine.

In order to investigate possible rebound effects of overstimulation with dopamine followed by abrupt dopamine withdrawal, a group of rats was treated for five days with l-dopa (a substance which is converted to dopamine in the brain). The research is described in an article in the December 2008 issue of Nutrition & Metabolism. After treatment was completed, the rats in the previously-treated l-dopa group were compared with an untreated control group. Over the next 12 weeks both groups of rats were allowed to eat as much food as they desired. At the end of that time, the previously-treated rats had gained 15% more weight than the control group.

Why did this happen? The authors hypothesize that treatment with the dopamine precursor l-dopa caused overstimulation of the dopamine signaling system in the rats. This, in turn, caused downregulation of dopamine receptors and decreased endogenous dopamine production. When the l-dopa treatment ceased, the rats were left with few dopamine receptors and low endogenous dopamine production. To compensate for this, the rats used the mechanism of overeating to compensate for their relative dopaminergic deficiency.

Rats are not humans. Nevertheless, it is possible to suggest that eating or tasting sweet food causes an overstimulation of the dopamine signaling system. This produces a downregulation of dopamine signaling such that, in the absence of sweet, there is a noticeable decrease in energy, motivation and mood. Sweets are legal, cheap and easy to obtain. If the sweet-eater wishes to experience the pleasant feelings associated with dopamine overstimulation, it will be very easy to continue eating sweets. And if he is unable to wait several days to a week to allow the body to return to its normal level of dopamine production and receptor activity, it will be harder than he might have expected to eliminate sweet tastes from his diet.

Detecting, Liking and Wanting Sweetness

Those who read food labels realize that high fructose corn syrup is added to all sorts of products, from pickles to yogurt to spaghetti sauce. The Corn Refiners Association says this is because high fructose corn syrup enhances flavor and increases shelf life. A recent article in the journal Physiology and Behavior suggests that there may be another reason.

The article, called Modified sham feeding of sweet solutions in women with and without bulimia nervosa, was designed to show whether people who experience binge-eating episodes might overrespond to the stimulations of taste and smell. As it turns out, they do not, or at least they did not in this study. However, the study did produce an interesting outcome in terms of the way people respond to sweet tastes.

The study compared two groups of women--ten healthy women (termed NC, or Normal Control) and eleven women with Bulimia Nervosa (termed BN). The women were given solutions of cherry-flavored Kool-Aid sweetened with aspartame in concentrations of 0, 0.01, 0.03, 0.08 and 0.28%. (The 0.08% solution approximates the sweetness of commercial soda.) There were three trials in which the five solutions were prepared in five opaque containers, each fitted with a straw. The solutions were presented in a random order, using a one-minute access period during which the women could sip as much as they wanted of that particular solution, but they could not swallow it. They were instructed to spit out the solution into another opaque container. (The amount sipped and the amount spit out was later measured by the investigators.) The women were then asked to

1. Rate the sweetness of the solution

2. Rate how well they liked the solution

3. Rate how much they wanted more of the solution

Even though the solutions were presented in random order, both the Normal Control group and the Bulimia Nervosa group were able to accurately distinguish among the five levels of sweetness provided in the solutions. Again, although the solutions were presented randomly, both the Normal Control group and the Bulimia Nervosa group reported liking the solutions in direct proportion to how sweet the solutions were. Consistent with the self-reported preference rating, both groups sipped an increasing amount of the solution as the sweetness of the solution increased. (Remember, they were not allowed to swallow the solution, but they could sip as much of it as they wanted.) Finally, as shown in the graph below, both groups reported that they wanted more of the solution as the sweetness of the solution increased.
For both groups of women, more sweetness led to more liking, more sipping and more wanting. This was not a function of actually consuming the sweetened solutions, but simply of having the solutions in their mouths for a few seconds. Using this information, it not unreasonable to suggest that the increased use of another sweet substance, high fructose corn syrup, in all sorts of foods, may have the unintended result of producing more liking, more eating and more wanting of the products that contain it.

But you have to eat carbohydrates!

Perhaps you overdid it a bit at Christmas and are looking for a weight-loss plan. Although low-carb diets are currently out of fashion, they have one big advantage over low-calorie, low-fat diets. They work.

Ordinary people can lose weight and keep it off by following a low-carb eating plan. Not only that, they will notice an improvement in blood pressure, HDL cholesterol, triglycerides, and insulin responsiveness. So why don't more people attempt weight loss through the low-carb lifestyle?

One big reason is that people are told (incorrectly) that their body requires them to eat a certain amount of carbohydrate every day. The brain requires glucose to function, and several other tissues require carbohydrate-derived fuels as well. If a person doesn't eat any carbohydrates, where does this fuel come from?

It comes from proteins. After proteins are eaten, they are broken down into their building blocks, which are called amino acids. These amino acids can be reassembled into other proteins. Some of them can be converted into fat. And thanks to a metabolic process called gluconeogenesis, up to 400 grams of them per day can be converted into carbohydrates.

Since the brain requires only about 120 grams of carbohydrates a day, that's well within a safe range. It does take a few days for the enzymes of gluconeogenesis to be induced, permitting conversion of enough glycogenic amino acids into glucose to supply the tissues that require it. During the transitional period, typical symptoms may include body aches, nausea and headaches. These will subside after about three days, and energy levels and alertness will improve noticeably. To figure out how much protein to eat to permit adequate carbohydrate synthesis, Jenny Ruhl has provided this convenient Protein Need Calculator.

If you need to start a weight-loss plan, there are many good diets available, including many versions of low-carb diets. Check out your options and pick the diet that suits you the best. And if you choose the low-carb lifestyle, be assured that thanks to gluconeogenesis, you can safely drop most or even all of the carbohydrates from your menus!

Type 1.5 Diabetes

Type 1.5 diabetes, as the name implies, falls between type 1 and type 2 diabetes. It manifests some of the symptoms of both types, and it is important because it affects about 15% of those diagnosed with diabetes.

Type 1 diabetes is characterized by the presence of autoantibodies against insulin or against certain components of the insulin-producing system such as glutamic acid decarboxylase (GAD), tyrosine phosphatase or the islet cells themselves. These autoantibodies cause the patient's own immune system to kill the beta cells of the pancreas, making the patient unable to produce any endogenous insulin.

Type 2 diabetes is characterized by insulin resistance and diminished production of insulin by the pancreas. If a patient is well-managed, this kind of diabetes can be controlled for many years by diet, excercise and oral medication.

Type 1.5 diabetes has characteristics of type 1 and type 2. Like type 2, its onset is in adulthood, and the pancreas is able to produce insulin for several years. Like type 1, it often occurs in thin people, and it often involves autoantibodies to GAD or islet cells. Unlike type 1, in type 1.5 diabetes, the autoantibodies work much more more slowly. However, their destruction of beta cells is relentless, and within 5-10 years of diagnosis, patients with type 1.5 diabetes will require insulin.


Type 1.5 diabetes is sometimes called Mature Onset Diabetes of the Young (MODY), Latent Autoimmune Diabetes in Adults (LADA), slow onset type 1 diabetes, or double diabetes. As might be expected, each of these terms involves specific criteria and there is disagreement about who falls into which category. Leaving the questions about specific terminology aside, why should it matter that about 15% of the diabetic population is neither type 1 nor type 2?

It matters because type 1.5 diabetics are often misdiagnosed as type 2 diabetics. It matters because type 1.5 diabetics will initially respond to dietary modifications and oral medication, but because their condition stems from the death of beta cells rather than insulin resistance, eventually they will not. Physicians who are not familiar with type 1.5 diabetes may not understand why a misdiagnosed type 1.5 diabetic has stopped responding to standard treatments and may assume that the patient is no longer complying with their instructions. (This happens often enough that physicians have good reason to suspect noncompliance as an explanation for poor diabetic control.) If the patient knows that he or she is following the doctor's guidelines, it might be a good idea to ask for autoantibody tests to see if destruction of the pancreatic beta cells is taking place. As in every other aspect of health care, it becomes important for the patient to become an active participant in the monitoring and management of his condition.

Type 2 Diabetes

Type 2 diabetes is a condition affecting slightly more than 7% of Americans. It used to be called adult-onset diabetes, but we now know it can occur in children as well as in adults. Another term for it was non-insulin-dependent diabetes mellitus (NIDDM), but about 30% of type 2 diabetics are treated with insulin.

Type 1 diabetes begins with death of insulin-producing beta cells in the pancreas. Typically this happens over a period of weeks or months and is not reversible. Type 2 diabetes may begin with a diminished production of insulin by the pancreas. Several risk alleles have been identified and have been found to have an additive effect, resulting in decreased glucose sensitivity in the pancreas of people who have not yet developed overt diabetes. This condition may go undetected for years, only becoming evident when the patient starts to experience insulin resistance. Often this happens during pregnancy, when the mother's body becomes less responsive to insulin during the third trimester. Gestational diabetes is a temporary condition, but can be an early indicator of a predisposition to type 2 diabetes. More often, as a person ages and becomes overweight, his or her muscles, liver and pancreas gradually develop increasing resistance to the action of insulin, and the symptoms of hyperglycemia start to appear. Insulin resistance in the liver may lead to overproduction of glucose by the liver, causing even more hyperglycemia. Hyperglycemia, in turn, may initiate a process called apoptosis (programmed cell death) in the pancreas, resulting in a pancreas that is significantly smaller and less able to produce insulin than the pancreas of a person who does not suffer from type 2 diabetes.

Unlike type 1 diabetes, the progression to type 2 diabetes usually occurs over several years. It does not typically result in the death of all the beta cells of the pancreas, but the ability of the pancreas to regulate blood glucose is significantly compromised. The presence of a genetic component is even more significant than it is in type 1 diabetes. In fact, if a person has a relative with type 2 diabetes, chances are 80% that the person will develop type 2 diabetes in his or her lifetime. With that in mind, it is a good idea to monitor fasting and postprandial glucose levels to see if blood sugars are starting to trend outside the normal range. If symptoms are detected early and the condition is managed appropriately, the progression to fullblown type 2 diabetes can be slowed or perhaps prevented altogether.

If you would like to do some more reading on the progression to type 2 diabetes, here are some links:

Metabolic Syndrome

Reactive Hypoglycemia

Reversing Insulin Resistance

(For those who are interested, the picture at the top is a Texas snowman.)

Type 1 Diabetes

The pancreas is a multifunctional organ that sits below and behind the stomach. As an exocrine organ, it empties digestive enzymes into the gut at the level of the duodenum. The pancreas is also an endocrine organ, synthesizing insulin in its beta cells and glucagon in its alpha cells, and secreting those hormones into the blood.

Normally the pancreas performs its functions silently and efficiently. However in some cases the beta cells of the pancreas are vulnerable to an attack by the body's own immune system. For about three million Americans, the pancreatic beta cells are no longer functional, resulting in a condition called type 1 diabetes.

The cause of type 1 diabetes is not entirely clear. The peak age of diagnosis is 14 years, but type 1 diabetes can develop at any age. There is a genetic contribution--twenty percent of patients have a relative who also has the disease. The presence of other autoimmune disorders is a predisposing factor, and childhood viral infections such as rubella, cytomegalovirus and coxsackie B may trigger the condition. In any case, in these patients the body's immune system targets the beta cells of the pancreas and renders them unable to produce insulin.

Before Drs. Banting and Best discovered insulin in 1921, the diagnosis of type 1 diabetes was a death sentence. Victims had continuous thirst and voracious appetites, but without endogenous insulin to control their blood sugar, they wasted away because they could not properly utilize the food they ate. A very low carbohydrate diet could forestall the inevitable for several years, but most died before the age of 30.

With the advent of exogenous insulin therapy, a new set of problems arose for type 1 diabetics. Blood glucose could be controlled, but if it was poorly controlled, it would eventually result in eye, kidney and nerve diseases. If too much insulin was injected, it could result in severe hypoglycemia and even death. Dr. Richard K. Bernstein is a physician who developed type 1 diabetes in 1946 at the age of 12. He tells a fascinating story, showing how difficult it was in those days to match insulin dose to blood glucose level. The advent of the glucometer enabled patients to monitor their blood glucose much more accurately, but it also led to the temptation to eat large amounts of carbohydrates and then "cover" the carbs with injected insulin.


Today the American Diabetes Association recommends that diabetics eat 25-35% of calories from fat, 15-20% from protein and 45-55% from carbohydrates. By contrast, Dr. Bernstein proposes that eating a large number of calories as carbohydrates produces a large variability in blood glucose and a high level of difficulty in controlling blood sugar. To counteract this, he suggests something called the Laws of Small Numbers, which entails eating only small amounts of slow-acting carbohydrate, and no fast-acting carbohydrate at all.

Which approach is correct? No definitive scientific comparison is available, but this review notes that when the ACCORD study attempted tight glycemic control in type 2 diabetics through drug therapy, the study had to be terminated because of high mortality. By contrast, the reviewers cite a long list of references that indicate that dietary control of hyperglycemia is able to improve many of the long-term consequences of diabetes. Type 1 diabetics are unable to completely avoid the use of exogenous insulin, but the strategy of eating very small amounts of carbohydrate that require only small amounts of insulin, appears to be worth serious consideration.

Metformin

Metformin (brand name Glucophage) is a member of the class of antidiabetic drugs called biguanides. Unlike the sulfonylureas such as glipizide, metformin does not decrease blood glucose by increasing the plasma concentration of insulin. Instead it works in several other ways to accomplish its purpose.

Metformin exerts its main effect, suppression of gluconeogenesis, by inhibiting the ATP production of the mitochondrial respiratory chain. Mitochondria are little organelles inside most of the cells of our bodies. Their job? To convert the precursor molecule ADP (adenosine diphosphate), into ATP (adenosine triphosphate), a molecule that is used to provide the energy required for many metabolic processes. Our bodies produce a little ATP by breaking down glucose in a process called glycolysis. But most of our ATP is provided when two-carbon units enter the tricarboxylic acid (TCA) cycle and are burned in the mitochondrial respiratory chain to produce carbon dioxide and water. From that link, here is a pictorial representation of the mitochondrial respiratory chain.


When metformin interferes with the conversion of ADP to ATP, the ratio of ATP to ADP decreases. When this ratio decreases, there is a resultant decrease in the activity of pyruvate carboxylase, which is the first enzyme used in the process of gluconeogenesis. The inhibition of pyruvate carboxylase significantly decreases the amount of gluconeogenesis the liver can perform. As we have seen previously, when the liver becomes insulin resistant, it will raise blood glucose by continuing to do gluconeogenesis even when blood sugar levels are normal. Although metformin does nothing directly to reverse insulin resistance in the liver, it is able to use the complex series of events beginning with the inhibition of ATP production in mitochondria to partially block the synthesis of excess glucose by the liver.

(As an aside, the inhibition of gluconeogenesis may cause an increase of lactic acid in the blood, lactic acid being one of the building blocks used for gluconeogenesis. In extreme cases this can lead to lactic acidosis, but the phenomenon is relatively rare with metformin.)

The second major effect of metformin is that it is able to decrease blood glucose by improving glucose uptake in muscle cells. Glucose cannot pass into muscle cells simply by diffusion; it requires specfic transport proteins to carry it into the cell. Studies have shown that metformin increases the number of the glucose transporters GLUT1 and GLUT4 in the plasma membrane of muscle cells. More glucose transport proteins means more glucose can be moved into insulin-resistant muscle cells, which in turn lowers blood glucose.

Although metformin has several other actions that reduce blood glucose, these two are the major ones. Unlike injected insulin, or oral drugs that increase insulin secretion, metformin does not cause an increase in insulin resistance, nor does it cause weight gain. However, it is important to note that metformin does not reverse insulin resistance. It simply acts to lower blood glucose in a non-insulin dependent manner.

Alcohol and the Low-Carb Lifestyle

About six weeks ago, Woodswalker asked me to write a post addressing the role of alcohol in a low-carb diet. This is a huge topic, but I will present a few thoughts for consideration. If you have questions or comments, please remember that I am a biochemist, not a psychiatrist.

Alcohol, also known as ethanol, contains seven calories per gram. That's somewhat less than fat at nine calories per gram, and quite a bit more than carbs and protein at four calories per gram. Pure grain alcohol contains zero carbs. It is not an essential food. The metabolism of ethanol is fairly straightforward.

The first pathway happens mainly in the liver and is constitutive. ADH is the enzyme alcohol dehydrogenase. ALDH is the enzyme acetaldehyde dehydrogenase, and TCA stands for the tricarboxylic acid (Krebs) cycle. The second pathway is also found in the liver and is inducible--that is, it can be upregulated if the body is required to detoxify large amounts of alcohol on a consistent basis. MEOS stands for mitochondrial ethanol oxidizing system.

If a meal is consumed that contains alcohol, carbs, protein and fat, the calories from the alcohol will be processed first. This means that fat will not be used for energy until all the calories from the ingested alcohol have been burned. If a signficant number of calories of alcohol are ingested, this will postpone or even prevent fat burning. Drinking hard (i.e., distilled) liquor by itself does not affect insulin secretion, but when hard liquor is consumed with food, it increases insulin resistance and insulin secretion. Hard liquor also contains quite a few calories per ounce. By contrast, an ounce of mixed drinks, wine or beer will have fewer calories from ethanol. However, mixed drinks, wine and beer all contain carbohydrates, and, if they are consumed in quantity, will result in insulin secretion and eventual weight gain.

According to Dr. Michael Eades (see the comment at 31 October 2008, 21:34), a single glass of dry wine per day can improve insulin sensitivity and can assist with weight loss. For those who can stop at one glass of wine, that's great. But remember that alcohol is a psychoactive drug, and as such, it lowers inhibitions. In the low-carb context, it is important to note that alcohol can lower inhibitions against consuming carbs, and inhibitions against consuming a second glass of wine as well.

Alcohol stops gluconeogenesis. Gluconeogenesis is the process used by the liver to keep blood glucose levels within normal limits. If a person consumes lots of carbohydrates, an alcohol-induced cessation of gluconeogenesis will probably not even be noticed. However, if a person consumes alcohol while doing very low-carb, he is likely to experience a fall in blood sugar followed by a compensatory release of adrenaline. This can lead to heart palpitations which will be relieved by drinking orange juice or eating a high-glycemic food. Unfortunately, this regimen is not conducive to longterm success on a low-carb diet. If a low-carber notices that alcohol consumption is followed by the symptoms of low blood sugar, it may be necessary for him to drink less than a full serving to minimize the undesirable side effects.

More on Insulin Control

The previous post discussed a three-legged stool approach to dealing with reactive hypoglycemia. The three legs of the stool are critical for lowering blood insulin and restoring insulin responsiveness. They are:

-Eating low-carb
-Eating moderate protein
-Waiting 5-6 hours between meals

Overall, these three appear to be the most important strategies for lowering blood insulin and restoring insulin responsiveness. However, a scan of low-carb websites suggests some additional ideas for improving insulin control.





-Avoid "sweet"
For 18 days Jimmy Moore did a "Sweet"-Free Challenge. He avoided all artificial sweeteners, including those in diet soda. The taste of sweet, even if it comes in a zero-calorie product, can be enough to trigger an insulin release from the pancreas.

-Be careful with alcohol
Dr. Mike Eades discusses alcohol consumption in the comments section of a recent post at his blog. In response to a commenter, Lowcarb convert, Dr. Mike says Studies have shown that a glass of wine per day helps with weight loss, but if you can’t stop with just one - and I’m one of those who has difficulty in doing so - cold turkey may be the better strategy. In response to that, another poster, Tom, says For me, wine is a gateway drug…to carbs! Alcohol lowers inhibitions, including inhibitions against eating carbs, and eating carbs leads to the release of insulin. A word to the wise is sufficient.

-When you eat carbs, make them low-glycemic carbs
Dr. William Davis discusses Quieting the insulin storm in a recent post at his blog. He points out that some foods, like wheat and cornstarch, have a higher glycemic index than table sugar. The higher the glycemic index, the more rapidly blood sugar will rise, and the more insulin will be released by the pancreas in response.

-Eat healthy fats at every meal
Healthy fats make up the caloric difference between an individual's daily caloric need and the calories provided by low carbs plus moderate protein. Fats provide energy, promote satiety and can be consumed with no insulin required whatsoever.

-Avoid eating a large volume of food at one sitting
In his book The Diabetes Solution, Dr. Richard Bernstein discusses the fact that simply overstretching the stomach causes the release of insulin. This effect happens without reference to what type of food is consumed. It occurs whenever the stomach has been distended--by overeating or by eating large servings of high fiber foods. (According to Dr. Bernstein, it even happens when the stomach is distended with air.) To avoid oversecreting insulin, it is preferable to avoid eating one large meal and two small ones, but instead keep all three meals at a similar volume of food.