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.