Reducing your protein intake can help manage metabolic syndrome and some of its main symptoms, such as obesity, diabetes and hypertension. This was shown by a study carried out by Brazilian and Danish researchers with the aim of comparing the effects of protein and calorie-restricted diets in humans. The results were published in the journal nutrients.
Metabolic syndrome is a cluster of conditions — including hypertension, high blood sugar, accumulation of fat around the waist and high cholesterol — that increase the risk of heart disease, stroke and diabetes.
“The study showed that decreasing protein consumption to 0.8 gram [g] per kilo [kg] of body weight was sufficient to achieve almost the same clinical results as a calorie-restricted diet, but without the need to reduce calories ingested. The results suggest the possibility that protein restriction is one of the main factors leading to the known beneficial effects of food restriction. Thus, the protein-restricted diet may be a more attractive nutritional strategy and relatively simpler to be followed by individuals with metabolic syndrome”, says Rafael Ferraz-Bannitz, PhD from FMRP-USP (School of Medicine of Ribeirão Preto, University of São Paulo) and first author of the article.
The study was funded by Fapesp through a Ferraz-Bannitz doctoral scholarship and a Thematic Project coordinated by Unicamp (State University of Campinas) professor Marcelo Mori, whose objective is to mimic, through different strategies, the effects of restriction caloric.
The investigation involved a multidisciplinary and international team with scientists from USP, the University of Copenhagen (Denmark), Inca (National Cancer Institute) and Cepid (Center for Research on Obesity and Comorbidities) — a Center for Research, Innovation and Dissemination of Fapesp based at Unicamp.
controlled diet
For 27 days, the researchers followed 21 patients diagnosed with metabolic syndrome. The volunteers were divided into two groups and remained hospitalized at the Hospital das Clínicas da FMRP-USP for the entire period, so that the diet could be monitored and strictly followed.
Each participant’s daily caloric requirement was calculated based on basal metabolism (energy expenditure at rest). In one group, patients were given an individualized diet with 25% fewer calories than what was considered ideal. In this case, the choice of food was made according to the standard recommended for the general population (50% carbohydrate, 20% protein and 30% fat).
In the second group, daily caloric consumption was also calculated individually based on basal metabolism. And, although the calorie value indicated for each individual was respected (never exceeded), the proportion of protein in the diet was reduced, remaining around 10% (60% carbohydrate and 30% fat). An important fact is that there was no difference in the use of salt. In both groups, patients consumed 2 g of salt per day.
The study showed that both the calorie-restricted and protein-restricted diets promoted weight loss due to reduced body fat and thereby improved the symptoms of metabolic syndrome. It is known that the reduction in adipose mass is associated with a reduction in blood glucose, lipid levels and blood pressure.
“After 27 days of monitoring, the two groups had similar results: reduced blood glucose levels, weight loss, blood pressure control and a drop in triglyceride and cholesterol levels. Both the calorie-restricted diet and the one that reduced protein consumption improved insulin sensitivity after treatment.Patients also had a decrease in body fat, especially in the abdominal and hip region, but without a reduction in lean mass [músculos]”, says Maria Cristina Foss de Freitas, professor at FMRP-USP and coordinator of the study.
The results confirm previous research carried out on mice. “But this time, we were able to carry out a randomized and fully controlled clinical study for 27 days, with a personalized menu according to the needs of each patient”, emphasizes Foss de Freitas.
In this way, it was possible to show, in humans, that it is enough to manipulate the macronutrients of a diet —protein, fat or carbohydrate- to obtain the beneficial effects of a food restriction. “We saw that protein restriction is enough to reduce body fat and maintain lean mass. This is very important, because in many restrictive diets, weight loss is also associated with a decrease in muscle mass”, comments Ferraz-Bannitz.
The study did not describe the molecular mechanisms that may explain the beneficial effects of the protein-restricted diet, but the researchers assume that minimal protein consumption promotes an alteration in the patients’ metabolism, or an improvement in the body’s energy capacity to provide the burning of energy. fat as a form of energy production for cells.
“We only have hypotheses left, and one of them would be the activation of molecular pathways that interpret the reduction of essential amino acids as a sign of reduced food intake, thus leading to the production of hormones normally increased during fasting. Studies in animal models have already shown that these pathways are involved both in the effects of the calorie-restricted diet and in the protein-restricted diet, causing fat loss in both cases”, says Mori.
Even with the promising results, it is necessary to pay attention to the fact that the study relied on the use of individualized diets. Mori also points out that the research was carried out with a specific population: patients with metabolic syndrome who had diabetes, obesity, hypertension and high cholesterol.
“However, it is difficult not to think about extrapolating this result. We know that a vegan diet has been shown to be positive for cases of metabolic syndrome and it has also been verified that excess protein intake, as is the Western standard, can be a problem. Therefore, it is necessary to evaluate case by case. One cannot forget that the lack of protein can lead to serious problems – something that has already been well described in the case of pregnant women, for example”, he says.
The article Dietary Protein Restriction Improves Metabolic Dysfunction in Patients with Metabolic Syndrome in a Randomized, Controlled Trial can be read at: www.mdpi.com/2072-6643/14/13/2670.