Obese Dieters' Brain May Thwart Their Weight-loss Efforts

People are motivated to lose weight, especially those who are obese or overweight. But despite their best efforts they may be unsuccessful in their attempt. Researchers now have found the reason for the failure of their weight loss plan.

"When obese persons reduce their food intake too drastically, their bodies appear to resist their weight loss efforts. They may have to work harder and go slower in order to outsmart their brain chemistry," said Gregory G. Freund, a professor in the U of I College of Medicine and a member of U of I's Division of Nutritional Sciences. He particularly cautions against beginning a diet with a fast or cleansing day, which appears to trigger significant alterations in the immune system that work against weight loss. "Take smaller steps to start your weight loss and keep it going," he said.
In the study, the scientist compared the effects of a short-term fast on two groups of mice. For 12 weeks, one group consumed a low-fat diet (10 percent fat); the other group was fed a high-fat (60 percent fat) and had become obese. The mice were then fasted for 24 hours. In that time, the leaner mice lost 18 percent of their body weight compared to 5 percent for the obese mice.
Freund said that there is an immune component to weight loss that has not been recognized. "Our data show that fasting induces an anti-inflammatory effect on a lean animal's neuroimmune system, and that effect is inhibited by a high-fat diet. Some of the brain-based chemical changes that occur in a lean animal simply don't occur in an obese animal," he said.