A pilot study indicates that eating less protein may improve the health of people with metabolic syndrome. A researcher says that the discovery should be verified in a larger study, including determining the underlying mechanism.
Research has shown that many people can reduce their blood glucose level through a well-planned diet with fewer calories.
Fewer calories lead to weight loss, higher insulin sensitivity, lower cholesterol levels, lower blood pressure and lower blood glucose, and that is one way to eliminate metabolic syndrome.
Now a new study shows that the people who have difficulty sticking to a calorie-restricted diet may be able to take a shortcut.
Instead of reducing calories, eating less protein may be sufficient.
To avoid feeling hungry on a low-calorie diet, people can change the composition of their diet and eat less fish, meat, nuts, cheese and milk, all of which contain a lot of protein.
“In our study, we found that a protein-restricted diet had the same benefits as a calorie-restricted diet on various measurable parameters for people with metabolic syndrome. This opens up a whole new approach to treating and curing metabolic syndrome if the results can be replicated in a larger study,” explains a researcher involved in the study, Jonas Thue Treebak, Associate Professor, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen.
The research has been published in Nutrients.
Animal studies indicate the health benefits of eating less protein
Jonas Thue Treebak explains that the starting-point for the study is animal studies indicating that eating less protein can have various health benefits.
High protein intake typically leads to increased circulation of branched-chain amino acids, and good evidence indicates that this is associated with the development of metabolic syndrome.
Research on mice has also shown that eating less protein can extend both their lifespan and their healthspan.
Another study has shown that removing methionine from animals’ diet has the same benefits as calorie restriction on various parameters of metabolic health.
“We wanted to examine the many indications that eating less protein can benefit people,” says Jonas Thue Treebak.
21 participants with metabolic syndrome
In the study, the researchers included 21 men and women with metabolic syndrome, which includes type 2 diabetes, hypertension and dyslipidaemia. The study was conducted at the University of São Paulo in Brazil.
The participants were hospitalised during the 27-day trial to monitor their food intake for compliance. One group ate a calorie-restricted diet with 25% fewer calories than their required energy consumption.
The other group received the number of calories that matched their basal energy expenditure but less protein: 10% of total energy instead of 20%.
The researchers measured various parameters of metabolic health before, during and after the intervention.
Improvement in all parameters
The results show that restricting dietary protein generally had the same effect on metabolic health as restricting calories.
In both groups, the resting heart rate declined from around 80 to around 60. According to Jonas Thue Treebak, this is a big reduction that indicates vast improvement in metabolic health. He acknowledges, however, that some of this effect may result from the participants being hospitalised and therefore not being exposed to everyday stress during the trial.
Most striking, however, was how these diets affected insulin sensitivity, which directly measures how well insulin removes glucose from the bloodstream. Insulin sensitivity improved by 62% in the calorie-restricted group and by a whopping 93% in the protein-restricted group.
The clinical cut-off for determining whether a person has type 2 diabetes is long-term blood glucose of 48 mmol/mol, so that people with readings below this are not considered to have type 2 diabetes.
Some of the participants in both groups went under that value during the 27 days and could be declared to be cured in principle.
Fasting blood glucose also dropped considerably for both groups from about 18 to 6 mmol/mol.
“The study indicates that changing the diet in various ways to eat less protein or fewer calories may potentially improve the control of metabolic syndrome, as long as the diet contains the essential amino acids. I would call this a very promising pilot study with interesting perspectives,” explains Jonas Thue Treebak.
Eating less protein may be appropriate for some people
Jonas Thue Treebak would like more trials testing protein restriction to improve metabolic control in type 2 diabetes.
Many people want to improve metabolic control but struggle with the restrictive approach to their diet. Compliance is the biggest challenge, and for some people, a diet in which they continue to eat the same amount of carbohydrate but less protein might be a better solution.
If further studies can confirm that protein restriction can lead to better metabolic control, the big question is how this happens. Jonas Thue Treebak would have liked to investigate this.
“Before the trial, we hypothesised that this could happen by changing the composition of the gut microbiome, but we found no overall differences in this parameter when comparing people in the protein-restriction group before or after the treatment. We also analysed the global gene expression in subcutaneous adipose tissue, but neither of the diets led to significant changes in overall gene expression. Therefore, we still do not know how eating less protein leads to better metabolic control of blood glucose and other clinically relevant parameters. Examining this in future larger studies will be relevant,” concludes Jonas Thue Treebak.
