March 29, 2021

NIH releases results of study on low-fat versus low-carb diets

NIH releases results of study on low-fat versus low-carb diets

The National Institutes of Health’s (NIH) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recently conducted a short-term study to compare the effects of a low-fat plant-based diet versus a low-carbohydrate animal-based diet on calorie intake, hormone levels, body weight, and more. The study was published in Nature Medicine.

“High-fat foods have been thought to result in excess calorie intake because they have many calories per bite. Alternatively, high-carb foods can cause large swings in blood glucose and insulin that may increase hunger and lead to overeating,” said NIDDK Senior Investigator Kevin Hall, Ph.D., the study’s lead author. “Our study was designed to determine whether high-carb or high-fat diets result in greater calorie intake.”

The study was performed in the NIH Clinical Center’s Metabolic Clinical Research Unit. Eleven men and nine women participated in the 4-week study. Participants were given either a plant-based, low-fat diet or an animal-based, low-carbohydrate diet for two weeks, immediately followed by two weeks on the alternate diet. The low-fat diet was high in carbohydrates. The low-carbohydrate diet was high in fats. Both diets were minimally processed and had equivalent amounts of non-starchy vegetables. The participants were given three meals a day, plus snacks, and could eat as much as desired.

The plant-based, low-fat diet contained 10.3% fat and 75.2% carbohydrate, while the animal-based, low-carb diet was 10% carbohydrate and 75.8% fat. Both diets contained about 14% protein and were matched for total calories presented to the subjects, although the low-carb diet had twice as many calories per gram of food as the low-fat diet.

The study concluded that people on a low-fat, plant-based diet ate fewer daily calories but had higher insulin and blood glucose levels, compared to when they ate a low-carbohydrate, animal-based diet, according to the small but highly controlled study. “Interestingly, our findings suggest benefits to both diets, at least in the short-term. While the low-fat, plant-based diet helps curb appetite, the animal-based, low-carb diet resulted in lower and more steady insulin and glucose levels,” Hall said. “We don’t yet know if these differences would be sustained over the long term.”