Low-carb diet is probably one of the most opted for strategy when it comes to losing weight, but researchers have found through a new study that low-fat diet is more effective and helps shed more body weight.
Carried out by researchers at the National Institute of Diabetes and Digestive and Kidney Diseases, the study counters the commonly accepted 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.
The research involved study of 19 non-diabetic men and women with obesity in the Metabolic Clinical Research Unit at the NIH Clinical Center in Bethesda, Maryland. The participants were confined 19 consenting adults with obesity to a metabolic ward for a pair of 2-week periods, over the course of which every morsel of food eaten was closely monitored and controlled.
Participants were asked to eat the same food and do the same activities. For the first five days of each visit they ate a baseline balanced diet. Then for six days, they were fed diets containing 30 percent 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.
At the end of the two dieting periods, the mathematical model proved to be correct. Body fat lost with dietary fat restriction was greater compared with carbohydrate restriction, even though more fat was burned with the low-carb diet. Researchers found that restricting dietary fat led to body fat loss at a rate 68 per cent higher than cutting the same number of carbohydrate calories when adults with obesity ate strictly controlled diets.
However, over prolonged periods the model predicted that the body acts to minimize body fat differences between diets that are equal in calories but varying widely in their ratio of carbohydrate to fat.
“There is one set of beliefs that says all calories are exactly equal when it comes to body fat loss and there’s another that says carbohydrate calories are particularly fattening, so cutting those should lead to more fat loss,” said Kevin Hall, PhD–a physicist turned metabolism researcher at the National Institute of Diabetes and Digestive and Kidney Diseases. “Our results showed that, actually, not all calories are created equal when it comes to body fat loss, but over the long term, it’s pretty close.”
“A lot of people have very strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking,” Hall says. “I wanted to rigorously test the theory that carbohydrate restriction is particularly effective for losing body fat since this idea has been influencing many people’s decisions about their diets.”
Hall does warn that people should refrain from making sweeping conclusions about how to diet from this study. The study’s purpose was to explore the physiology of how equal calorie reductions of fat versus carbs affect the human body. The research is limited by its sample size; only 19 people could be enrolled due to the expense of such research and the restrictiveness of the carefully controlled protocol.
“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.”