NIH study compares low-fat, plant-based diets to low-carb, animal-based diets

News release

Thursday, January 21, 2021

People on a low-fat, plant-based diet ate fewer daily calories, but compared to high insulin and blood sugar levels when they ate a low-carbohydrate, animal-based diet, a small but highly controlled nationally Institute of Health according to the study. The study by researchers at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) compared the effects of the two diets on calorie intake, hormone levels, body weight, and more. Published in, Conclusion Nature medicine, A broader understanding of dietary carbohydrates or restricting fats can affect health.

“High fat foods are thought to result in high calorie intake, as they contain many calories per calorie. Alternatively, high-carb foods can cause large swings in blood glucose and insulin that can increase appetite and overeat, ”said study lead author Kevin Hall, senior investigator at NIDDK. “Our study was designed to determine whether high-carb or high-fat diets consumed more calories.”

Researchers housed 20 adults without diabetes for four consecutive weeks at the Metabolic Clinical Research Unit of the NIH Clinical Center. Participants, 11 men and nine women, received either a plant-based, low-fat diet or an animal-based, low-carbohydrate diet for two weeks, followed immediately by two weeks on an alternative diet. A low-fat diet was high in carbohydrates. A diet with a low carbohydrate was high in fat. Both diets were minimally processed and contained equal amounts of non-starchy vegetables. Participants are served food three times a day, as well as snacks, and they can eat as much as they like.

The main results showed that people on a low-fat diet ate 550 to 700 fewer calories per day than those on a low-carb diet. Despite the large difference in calorie intake, participants reported no difference in hunger, enjoyment of food, or fullness between the two diets. Participants lost their weight on both diets, but only a low-fat diet led to a significant loss of body fat.

“Despite eating with an abundance of high glycemic carbohydrates that resulted in a markedly swinging blood glucose and insulin, those eating a plant-based, low-fat diet showed a significant reduction in calorie intake and body fat loss. , Which challenges the idea. A high per high-carb diet leads people to an end. On the other hand, animal-based, low-carb diets did not increase weight despite being high in fat, “said Hall.

These findings suggest that the factors causing overweight and weight gain are more complex than the amount of carbs or fat in one’s diet. For example, Hall’s laboratory showed in 2019 that eating a diet high in ultra-processed food and weight gain compared to a minimally processed diet matched for carbs and fat.

The plant-based, low-fat diet had 10.3% fat and 75.2% carbohydrate, while the animal-based, low-carb diet had 10% carbohydrate and 75.8% fat. Both diets contained approximately 14% protein and were matched for total calories presented for subjects, although the low-carb diet had twice as many calories per meal as compared to the low-fat diet. On the low-fat menu, dinner may include a baked sweet potato, chickpeas, broccoli and oranges, while a low-carb meal may include beef stir fry with cabbage rice. The subject chose what they could eat and the food they were given though.

“Interestingly, our findings benefit both diets, at least in the short term. Although a low-fat, plant-based diet helps curb hunger, animal-based, low-carb diets result in lower and more stable insulin and glucose levels, ”Hall said. “We do not yet know whether this difference will be sustained in the long term.”

Researchers note that the study was not designed to make dietary recommendations for weight loss, and the results may be different if participants were actively trying to lose weight. In addition, all meals were prepared and participants were provided for an in-patient setting, which may be difficult to replicate outside the laboratory, where cost of food, availability of food, and lack of food preparation Factors such as this can challenge the diet. A tightly controlled clinical environment, however, ensures objective measurement of food intake and data accuracy.

Griffin P., director of NIDDK. “To help us achieve good nutrition, hard science is important and in light of the COVID-19 epidemic, we now want to identify strategies to stay healthy,” said Rodgers, MD. “This study brings us closer to answering long-standing questions about what we eat that affects our health.”

The research was supported by the NIDDK Intramural Research Program. Additional NIH support has come from the National Nursing Research Institute under grant 1Z1ANR000035-01.

About National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): NIDDK, a component of the National Institutes of Health (NIH), conducts and supports research on diabetes and other endocrine and metabolic diseases; Digestive diseases, nutrition and obesity; And kidney, urinary and hematoma diseases. For the full spectrum of therapy and afflicting people of all ages and ethnic groups, these diseases cover some of the most common, severe, and disabling conditions affecting Americans. For more information about NIDDK and its programs, see

About National Institutes of Health (NIH):The NIH, the nation’s medical research agency, consists of 27 institutions and centers and is a component of the US Department of Health and Human Services. The NIH is the primary federal agency conducting and supporting basic, clinical and translational medical research, and investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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The reference

Hall KD, et al. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nature medicine. January 21, 2021.



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