Thursday, July 10, 2008

Reversing Insulin Resistance

It is commonly thought that weight loss is required to reverse insulin resistance. A small study of obese type 2 diabetics indicates that this may not be the case. Ten diabetic patients, seven of whom were on diabetes medications, checked into a hospital with an average weight of 252 pounds. For seven days they acted as their own Control group. They ate their normal diets, averaging 3111 calories and 309 grams of carbohydrate a day. On day 7 their blood glucose and blood inuslin levels were measured over a 24 hour period. The time course of glucose and insulin is represented by the black circles in the graphs below.

On day 8 the patients remained in the hospital and became the Low-carbohydrate diet group. They were switched to a low-carbohydrate diet which included 21 daily grams of carbohydrate, plus as much fat and protein as they desired. Adherence to the low-carbohydrate diet was confirmed by measurement of urinary ketones. After two weeks on this diet, blood glucose and blood insulin levels were again measured over a 24 hour period. The time course of glucose and insulin after two weeks of eating low-carb is represented by the blue circles in the graphs above. (For the sake of reference, the 6mmol/L Glucose Level is roughly equivalent to a glucometer reading of 100 and the 8 mmol/L Glucose Level is roughly equivalent to a reading of 150.)

There were no set mealtimes, so all of the curves are fairly flat. Nevertheless, it is easy to see that a diet of 309 grams of carbohydrate a day produced high glucose levels around the clock and high insulin levels during waking hours. By contrast, just two weeks of eating 21 grams of carbohydrate a day brought blood glucose levels to a normal range and kept insulin levels low both during waking hours and at night.

Other measures of insulin resistance reflected the values shown in the graphs. In just two weeks on the low-carbohydrate regimen, glycosylated hemoglobin fell from 7.3% to 6.8%. Insulin sensitivity improved by approximately 75%, while plasma triglycerides decreased by 35% and cholesterol levels decreased by 10%.

During the last two weeks of the study, patient weights also decreased by an average of 1.8%. Although it might be possible to attribute the large improvement in lab values to this small decrement in weight, it seems more likely that both the weight loss and the rapid improvement in insulin resistance was attributable to the patients' adherence to a low-carbohydrate diet.

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