A study published in Cell Metabolism shows that restricting dietary fat may be more effective at lowering body fat than a low-carb diet.
The researchers studied 19 obese men and women over two extended visits during which time the participants ate the same food and took part in the same activities. For the first five days of each visit, the subjects ate a baseline balanced diet. Then for six days, they were fed diets containing 30% fewer calories, achieved by cutting either only total carbs or total fat from the baseline diet, while eating the same amount of protein. They switched diets during the second visit. During the study period, subjects were under 24-hr supervision.
The researchers found that the low-fat dieters lost an average of 3.1 oz per day over six days, whereas the low-carbohydrates dieters lost 1.9 oz per day. This means that the reduced fat dieters lost body fat at a rate 68% greater than a diet cutting calories through carb restriction.
Interestingly, despite the fact that only the carbohydrate-restricted diet led to decreased insulin secretion—which some have proposed is necessary to attain body fat loss—calorie for calorie, restriction of dietary fat led to greater body fat loss.
“In contrast to previous claims about a metabolic advantage of carbohydrate restriction for enhancing body fat loss, our data and model simulations support the opposite conclusion when comparing the restricted fat and restricted carbohydrate diets,” concluded the researchers.
The researchers did note, however, that their relatively short-term experimental study had obvious limitations in its ability to translate to fat mass changes over prolonged durations. It could be argued that perhaps the fat balance and body fat changes would converge with continuation of the diets over the subsequent weeks. The mathematical model simulations suggest that the diet with selective reduction in fat would continue to outpace the reduced carbohydrate diet over six months, but long term studies are needed.
