NIH study compares a low-fat, plant-based diet to a low-carb diet

Press release

Thursday, January 21, 2021

People on low-fat, plant-based diets ate fewer calories per day, but had higher insulin and blood sugar levels, compared to when they ate a low-carb, high-protein diet. animals, according to a small, highly controlled study from the National Institutes of Health. Led by researchers from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the study compared the effects of the two diets on calorie intake, hormone levels, body weight, and more. The results, published in Nature medicine, broaden understanding of the impact of restriction of carbohydrates or dietary fat on health.

“Foods high in fat are thought to lead to excessive calorie intake because they contain a lot of calories per bite. Alternatively, foods high in carbohydrates can cause large swings in blood sugar and insulin which can increase hunger and lead to overeating, ”said Kevin Hall, Ph.D., principal investigator of NIDDK, senior author of study. “Our study was designed to determine whether diets high in carbohydrates or fat lead to increased calorie intake.”

The researchers housed 20 adults without diabetes for four consecutive weeks in the metabolic clinical research unit at the NIH Clinical Center. The participants, 11 men and nine women, were given either a low-fat plant diet or a low-carbohydrate animal diet for two weeks, immediately followed by two weeks on an alternative diet. The low fat diet was high in carbohydrates. The low-carb diet was high in fat. Both diets were minimally processed and contained equivalent amounts of non-starchy vegetables. Participants were given three meals a day, plus snacks, and could eat as much as they wanted.

The main results showed that people on a low fat diet consumed between 550 and 700 calories less per day than when they were on a low carbohydrate diet. Despite the large differences in calorie intake, participants reported no difference in hunger, meal enjoyment, or satiety between the two diets. Participants lost weight on both diets, but only the low-fat diet led to significant body fat loss.

“Despite eating a diet rich in high glycemic index carbohydrates which resulted in marked swings in blood sugar and insulin levels, people on plant-based, low-fat diets showed significant reductions in calorie intake and loss of body fat, which challenges the idea that high-carbohydrate diets per se lead people to overeat. On the other hand, the animal-based low-carb diet did not result in weight gain despite being high in fat, ”Hall said.

These results suggest that the factors that cause overeating and weight gain are more complex than the amount of carbohydrate or fat in the diet. For example, Hall’s lab showed last year that a diet high in ultra-processed foods leads to overeating and weight gain compared to a low-processed diet that matches carbohydrates and fats.

The plant-based, low-fat diet contained 10.3% fat and 75.2% carbohydrates, while the animal-based, low-carbohydrate diet was 10% carbohydrate and 75.2% carbohydrate. 8% fat. Both diets contained about 14% protein and corresponded to the total number of calories presented to the subjects, although the low-carb diet contained twice as many calories per gram of food as the low-fat diet. On the low-fat menu, dinner might be a baked sweet potato, chickpeas, broccoli, and oranges, while a low-carb dinner might be beef stir-fry with rice. cauliflower. Subjects could eat whatever they chose and regardless of the quantity of meals they received.

“Interestingly, our results suggest benefits for both diets, at least in the short term. While the low-fat, plant-based diet helps reduce appetite, the low-carb, animal-based diet has resulted in lower and more stable insulin and glucose levels, ”Hall said. “We do not yet know if these differences would hold for the long term.”

The researchers note that the study was not designed to make dietary recommendations for weight loss, and the results may have been different if the participants were actively trying to lose weight. Additionally, all meals were prepared and provided to participants in a hospital setting, which can make results difficult to repeat outside of the lab, where factors such as food cost, food availability, and preparation constraints. meals can make it difficult to stick to diets. The tightly controlled clinical environment, however, ensured objective measurement of food intake and data accuracy.

“To help us achieve good nutrition, rigorous science is essential – and of particular importance now, in light of the COVID-19 pandemic, as we aim to identify strategies to help us stay healthy “Said NIDDK director Griffin P. Rodgers, MD” This study brings us closer to answering long-researched questions about how what we eat affects our health.

The research was supported by the intramural research program NIDDK. Additional support from NIH came from the National Institute for Nursing Research under grant 1Z1ANR000035-01.

About the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK): The 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 renal, urological and hematological diseases. Spanning the entire spectrum of medicine and affecting people of all ages and ethnicities, these diseases encompass some of the most common, serious and disabling conditions affecting Americans. For more information on the NIDDK and its programs, see http://www.niddk.nih.gov.

About the National Institutes of Health (NIH):NIH, the country’s medical research agency, comprises 27 institutes and centers and is part of the US Department of Health and Human Services. The NIH is the principal federal agency that conducts and supports basic, clinical and translational medical research, and studies the causes, treatments, and cures for common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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