Low-fat, plant-based diet compared to low-carb, animal-based diet in clinical trials – Here are the results

Low-fat, low-carbohydrate diet

People on a low-fat, vegetable-based diet ate fewer calories daily, but had higher levels of insulin and blood glucose, compared to when they ate a low-carb animal-based diet, according to a small but highly controlled at the National Institutes of Health. Led by researchers at 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 today (January 21, 2021) in Nature Medicine, broaden the understanding of how restricting carbohydrates or fats in the diet can affect health.

“Fat-rich foods are believed to result in excessive calorie intake because they have too many calories per bite. Alternatively, carbohydrate-rich foods can cause large fluctuations in blood glucose and insulin that can increase hunger and lead to overeating, ”said senior NIDDK investigator Kevin Hall, Ph.D., lead author of the study. “Our study was designed to determine whether diets high in carbohydrates or fats result in higher calorie intake.”

The researchers housed 20 adults without diabetes for four continuous weeks at the NIH Clinical Center’s Metabolic Clinical Research Unit. Participants, 11 men and nine women, received either a low-fat, vegetable-based diet or a low-carbohydrate diet based on animals for two weeks, immediately followed by two weeks on the alternative diet. The low-fat diet was rich in carbohydrates. The low-carb diet was high in fat. Both diets were minimally processed and contained equivalent amounts of starchless vegetables. Participants were given three meals a day, plus snacks, and could eat as much as they liked.

Plant-based diet versus meat-based diet

Examples of dinners given to study participants: low-carbohydrate diet based on animals (left) and low-fat diet based on vegetables (right). Credit: Amber Courville and Paule Joseph, NIH

The main results showed that people who were on a low-fat diet ate 550 to 700 fewer calories per day than when they were on a low-carbohydrate diet. Despite the large differences in calorie intake, participants did not report differences in hunger, pleasure in meals or satiety between the two diets. Participants lost weight on both diets, but only the low-fat diet led to a significant loss of body fat.

“Despite eating foods with an abundance of high glycemic index carbohydrates that resulted in pronounced fluctuations in glucose and insulin in the blood, people who ate the low-fat, plant-based diet showed a significant reduction in calorie intake and loss of body fat, which defies the idea that diets high in carbohydrates alone cause people to overeat. On the other hand, the animal-based, low-carb diet did not result in weight gain, despite being high in fat, ”said Hall.

These findings suggest that the factors that result in overeating and gaining weight are more complex than the amount of carbohydrates or fat in the diet. For example, Hall’s lab showed in 2019 that a diet rich in ultra-processed foods leads to overeating and weight gain compared to a minimally processed combined diet for carbohydrates and fat.

The low-fat, plant-based diet contained 10.3% fat and 75.2% carbohydrates, while the low-carbohydrate diet based on animals contained 10% carbohydrates and 75.8% fat. Both diets contained about 14% protein and were matched for the total calories presented to individuals, although the low-carb diet has twice as many calories per gram of food as the low-fat diet. On the low-fat menu, dinner can consist of roasted sweet potatoes, chickpeas, broccoli and oranges, while a low-carb dinner can be braised meat with cauliflower rice. Participants could eat what and how much they wanted from the 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 to reduce appetite, the low-carb, animal-based diet resulted in lower, more stable levels of insulin and glucose, ”said Hall. “We still don’t know whether these differences would be sustained in the long run.”

The researchers noted 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. In addition, all meals were prepared and provided to participants in an inpatient setting, which can make it difficult to repeat results outside the laboratory, where factors such as food costs, food availability and meal preparation restrictions can make the adherence to diets is a challenge. The tightly controlled clinical environment, however, ensured the objective measurement of food intake and precision Data.

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

Reference: “Effect of a low-fat, vegetable-based diet versus an animal-based ketogenic diet on ad libitum energy intake” by Kevin D. Hall, Juen Guo, Amber B. Courville, James Boring, Robert Brychta, Kong Y. Chen, Valerie Darcey, Ciaran G. Forde, Ahmed M. Gharib, Isabelle Gallagher, Rebecca Howard, Paule V. Joseph, Lauren Milley, Ronald Ouwerkerk, Klaudia Raisinger, Irene Rozga, Alex Schick, Michael Stagliano, Stephan Torres, Mary Walter, Peter Walter, Shanna Yang and Stephanie T. Chung, January 21, 2021, Nature Medicine.
DOI: 10.1038 / s41591-020-01209-1

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

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