A new study found obese adults who restricted dietary fat lost about 68 percent more body fat than those who cut carbs.
The study showed carb restriction lowered the production of the fat-regulating hormone insulin and increased fat burning, but this did not occur in diets that focused on controlling fat intake, the National Institutes of Health reported.
"Compared to the reduced-fat diet, the reduced-carb diet was particularly effective at lowering insulin secretion and increasing fat burning, resulting in significant body fat loss," said Kevin Hall, NIDDK senior investigator and lead study author. "But interestingly, study participants lost even more body fat during the fat-restricted diet, as it resulted in a greater imbalance between the fat eaten and fat burned. These findings counter the theory that body fat loss necessarily requires decreasing insulin, thereby increasing the release of stored fat from fat tissue and increasing the amount of fat burned by the body."
To make their findings, a team of researchers 19 non-diabetic men and women with obesity in the Metabolic Clinical Research Unit at the NIH Clinical Center. The participants stayed in the clinic for 24 hours per day for two extended visits where they consumed the same food and performed the same activities. For the first five days of each visit they ate the same baseline diet, and following that period were given a diet consisting of 30 percent fewer calories; the lower calorie diets were achieved by either cutting down on fat or carbs. In the second visit, the participants switched diets.
"Our data tell us that when it comes to body fat loss, not all diet calories are exactly equal," Hall said. "But the real world is more complicated than a research lab, and if you have obesity and want to lose weight, it may be more important to consider which type of diet you'll be most likely to stick to over time."
The findings were published in a recent edition of the journal Cell Metabolism.
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