20 January 2009
Washington, USA
{jumi usermod/ads/ads.php}{/jumi} A study conducted by scientists at UT Southwestern Medical Center has shown that people who consume low–carbohydrate diets depend more on the oxidation of fat in the liver for energy than those on a low–calorie diet.
The researchers say that their findings may have implications for treating obesity and related diseases like diabetes, insulin resistance and nonalcoholic fatty liver disease.
“Instead of looking at drugs to combat obesity and the diseases that stem from it, maybe optimizing diet can not only manage and treat these diseases, but also prevent them,” said lead author of the study Dr. Jeffrey Browning, assistant professor in the UT Southwestern Advanced Imaging Research Center and of internal medicine at the medical centre.
Even though the aim of the study was not to determine which diet was more effective for losing weight, the researchers observed that the average weight loss for the low–calorie dieters was about five pounds after two weeks, while the low–carbohydrate dieters lost about nine–and–a–half pounds.
Glucose, a form of sugar, and fat are both sources of energy that are metabolised in the liver, and used as energy in the body. Glucose can be formed from lactate, amino acids or glycerol.
With an eye on finding out how diet affects glucose production and utilization in the liver, the 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.
Advanced imaging techniques were used two weeks later to analyse the different methods, or biochemical pathways, the subjects used to make glucose.
“We saw a dramatic change in where and how the liver was producing glucose, depending on diet,” said Dr. Browning.
The researchers observed 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,” Dr. Browning said.
The team also observed that the different diets produced other differences in glucose metabolism, with people on a low–calorie diet getting about 40 percent of their glucose from glycogen, which is comes from ingested carbohydrates and is stored in the liver until the body needs it.
The low–carbohydrate dieters, on the other hand, were found to get only 20 percent of their glucose from glycogen. Instead of dipping into their reserve of glycogen, such subjects burnt liver fat for energy.
The significance of the findings lies in the fact that the accumulation of excess fat in the liver can result in nonalcoholic fatty liver disease (NAFLD) – a liver disease which is associated with metabolic disorders like insulin resistance, diabetes and obesity, and can lead to liver inflammation, cirrhosis and liver cancer.
“Energy production is expensive for the liver. It appears that for the people on a low–carbohydrate diet, in order to meet that expense, their livers have to burn excess fat,” Dr. Browning said.
Based on their observations, the researchers came to the conclusion that patients on the low–carbohydrate diet increased fat burning throughout the entire body.
Dr. Browning’s team will next study whether the changes that occur in liver metabolism as a result of carbohydrate restriction could help people with nonalcoholic fatty liver disease.
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The current study has been published in the journal Hepatology.
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