Cutting levels of dietary fat intake reduces body fat more than cutting intake of carbohydrates in obese patients, according to latest US research.
In the study, restricting dietary fat led to body fat loss at a rate 68% higher than cutting the same number of carbohydrate calories when adults with obesity ate strictly controlled diets.
“These findings counter the theory that body fat loss necessarily requires decreasing insulin”
Carbohydrate restriction lowered production of the fat-regulating hormone insulin and increased fat burning, whereas fat restriction had no observed changes in either insulin production or fat burning.
The study, which has been published in the journal Cell Metabolism, was conducted at a research unit at the US National Institute of Diabetes and Digestive and Kidney Diseases.
The researchers studied 19 men and women who were obese but did not have type 2 diabetes.
Participants stayed in the unit 24 hours per day for two extended visits, eating the same food and doing 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% 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.
Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of around 53g per day of body fat, fat oxidation was unchanged by fat restriction, leading to around 89g per day of fat loss – significantly greater than carbohydrate restriction.
Lead study author Dr Kevin Hall said: “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.
“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,” he said.
“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,” he added.