Protein restriction may be effective in fighting obesity and diabetes

According to a study conducted by researchers in Brazil and Denmark to compare the effects of protein and calorie restriction diets in humans. An article reporting the study is published in the journal Nutrients.

Metabolic syndrome is a group of conditions that increase the risk of cardiovascular disease, stroke, and diabetes, including high blood pressure, high blood sugar, excess body fat around the waist, and cholesterol levels abnormal.

“The study showed that reducing protein intake to 0.8 g per kg body weight was sufficient to achieve almost the same clinical results as calorie restriction, but without the need to reduce protein. caloric intake. The results suggest that protein restriction may be one of the key factors leading to the known benefits of dietary restriction. A protein restriction diet may therefore be a more appealing and easier-to-follow nutritional strategy for people with metabolic syndrome,” said Rafael Ferraz-Bannitz, first author of the paper and currently a postdoctoral researcher at the Joslin Diabetes Center of the Harvard Medical School in the United States. states.

The study was funded by FAPESP through a doctoral fellowship awarded to Ferraz-Bannitz while attending the Ribeirão Preto Faculty of Medicine at the University of São Paulo (FMRP-USP) in Brazil. The study also benefited from a FAPESP thematic project on strategies for mimicking the effects of dietary restriction, led by Marcelo Mori, a professor at the State University of Campinas (UNICAMP), also in Brazil.

A multidisciplinary team of scientists conducted the study, including researchers affiliated with the University of Copenhagen in Denmark, the University of São Paulo and the National Cancer Institute (INCA) in Brazil, as well as the Center Center for Research on Obesity and Comorbidities (OCRC), a Center for Research, Innovation and Dissemination (RIDC) funded by FAPESP and hosted by UNICAMP.

Controlled feeding

In the study, 21 volunteers with metabolic syndrome were analyzed over a 27-day period during which their diets were monitored. Throughout this period, they were hospitalized at the FMRP-USP University Hospital (Hospital das Clínicas in Ribeirão Preto).

The daily caloric intake of each volunteer was calculated according to the basal metabolic rate (energy expenditure at rest). One group was fed what the authors call a standard Western diet (50% carbs, 20% protein, and 30% fat) but with 25% fewer calories.

For the second group, protein intake was reduced to 10%. The caloric intake was adapted to the basic energy expenditure of each volunteer. Both groups consumed 4 g of salt per day.

The results showed that the calorie and protein restriction groups lost weight due to a decrease in body fat and that symptoms of metabolic syndrome improved. Decreasing body fat is known to be associated with lower blood sugar and more normal levels of lipids and blood pressure.

“After 27 days of monitoring, both groups achieved similar results in terms of lower blood sugar, weight loss, blood pressure control, and lower triglyceride and cholesterol levels. Both diets improved insulin sensitivity after treatment. Body fat decreased, as did waist and hip circumference, but without loss of muscle mass,” said Maria Cristina Foss de Freitas, final author of the paper and professor at FMRP-USP.

The results confirmed those of previous studies involving experiments on mice. “Here, however, we managed to conduct a fully controlled randomized clinical trial lasting 27 days, with a personalized menu designed to meet the needs of each patient,” said Foss de Freitas.

Manipulation of dietary macronutrients—proteins, carbohydrates, and fats—is sufficient to achieve the beneficial effects of dietary restriction. “We have demonstrated that protein restriction reduces body fat while maintaining muscle mass. This is important because weight loss from restrictive diets is often associated with loss of muscle mass,” Ferraz-Bannitz said.

The study did not investigate the molecular mechanisms that might explain the beneficial effects of protein restriction diets, but the researchers believe that low protein intake triggered a change in metabolism or improved the body’s energy management by causing it to burn fat in order to produce energy for cells. “We only have hypotheses at the moment. The first is that molecular pathways are activated to interpret the reduction in essential amino acids as a signal to reduce food intake while leading to the production of hormones that typically increase when we fast,” Mori said. “Studies in animal models have shown the involvement of these pathways in the effects of protein and calorie restriction, both of which result in fat loss.”

Despite the promising results of their studies, the researchers point out that the diets in question were personalized. Mori also pointed out that they were focusing on a specific population of patients with metabolic syndrome (obesity, diabetes, hypertension and abnormal cholesterol levels).

“Nevertheless, it is tempting to extrapolate the results. We know that research has shown that vegan diets are positive for cases of metabolic syndrome. It has also been found that the excessive protein intake common in the standard Western diet can be a problem. Each case should be analyzed on its own merits. We must not forget that protein deficiency can lead to serious health problems, as has been well described in pregnant women, for example,” he added.

About the São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution whose mission is to support scientific research in all areas of knowledge by granting scholarships, fellowships and grants to researchers linked to educational institutions University and Research from the State of São Paulo, Brazil. FAPESP is aware that the best research can only be done by working with the best researchers at the international level. Therefore, it has established partnerships with funding agencies, institutions of higher education, private companies and research organizations in other countries known for the quality of their research and has encouraged scientists funded by its grants to further develop their international collaboration. You can find out more about FAPESP at and visit the FAPESP news agency at to keep up to date with the latest scientific advances that FAPESP is helping to achieve through to its many programs, awards and research centers. You can also subscribe to the FAPESP press agency at

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