DALLAS—People on low-carbohydrate diets are more dependent on the oxidation of fat in the liver for energy than those on a low-calorie diet, according to a study from researchers at UT Southwestern Medical Center.
The findings, published in the journal Hepatology, could have implications for treating obesity and related diseases such as diabetes, insulin resistance and nonalcoholic fatty liver disease, said Jeffrey Browning, MD, assistant professor in the UT Southwestern Advanced Imaging Research Center and of internal medicine at the medical center.
"Instead of looking at drugs to combat obesity and the diseases that stem from it, maybe optimizing diet not only can manage and treat these diseases, but also prevent them," said Browing, the study’s lead author.
The study was not designed to determine which diet was more effective for losing weight; however, the average weight loss for the low-calorie dieters was about 5 pounds after two weeks, while the low-carbohydrate dieters lost an average of 9.5 pounds.
To determine how diet affects glucose production and utilization in the liver, researchers randomly assigned 14 obese or overweight adults to either a low-carbohydrate or low-calorie diet and monitored seven lean subjects on a regular diet. After two weeks, researchers used advanced imaging techniques to analyze the different methods the subjects used to make glucose.
Researchers found that participants on a low-carbohydrate diet produced more glucose from lactate or amino acids than those on a low-calorie diet.
"Understanding how the liver makes glucose under different dietary conditions may help us better regulate metabolic disorders with diet," Browning said.
The different diets produced other differences in glucose metabolism. Low-calorie dieters got about 40 percent of their glucose from glycogen, which comes from ingested carbohydrates, and is stored in the liver until the body needs it. Low-carb dieters got only 20 percent of their glucose from glycogen. Instead of dipping into their reserve of glycogen, the subjects burned liver fat for energy.
The findings are significant because the accumulation of excess fat in the liver—primarily a form of fat called triglycerides—can result in nonalcoholic fatty liver disease (NAFLD).
Browning previously has shown NAFLD may affect as many as one-third of U.S. adults. The disease is associated with metabolic disorders such as insulin resistance, diabetes and obesity, and it can lead to liver inflammation, cirrhosis and liver cancer.