By Maria Fernanda Ziegler  |  Agência FAPESP – A study conducted by researchers affiliated with the Federal University of São Carlos (UFSCar) in São Paulo state, Brazil, and University College London (UCL) in the United Kingdom shows that accumulated belly fat combined with weak muscles (dynapenia) is the condition that most heightens the risk of developing metabolic syndrome in people over 50.

“The risk of metabolic syndrome for individuals with dynapenia and abdominal obesity was 234% greater than for those with neither dynapenia nor obesity, and almost double the increase in risk for people with obesity only [126%]. Our findings show that dynapenia and abdominal obesity together entail augmented metabolic alterations,” said Tiago da Silva Alexandre, a professor in the Department of Gerontology at UFSCar and principal investigator for the study, which was supported by FAPESP. 

The study involved an analysis by UFSCar’s researchers of a database for 3,952 participants in the English Longitudinal Study of Ageing (ELSA) aged over 50 to investigate development of metabolic syndrome in an eight-year follow-up period (2004-13). An article describing the study and its findings is published in the Journal of Nutrition, Health and Aging.

In light of the results, the researchers emphasized the importance of regular aerobic exercise and resistance training to maintain muscle strength and prevent metabolic syndrome during aging.

Altered metabolism

Metabolic syndrome, the main risk factor for cardiovascular disease, is clinically diagnosed when at least three of the following conditions are present: obesity, high blood triglycerides, high blood sugar, low good cholesterol (HDL), and high blood pressure. 

According to the researchers, muscle metabolism dysfunction associated with loss of strength explains the significance of muscular weakness for the heightened risk represented by metabolic syndrome. “Fat infiltrates weak muscles, causing not only further loss of strength but also a number of metabolic alterations in the tissue that reduce insulin signaling and lead to insulin resistance, altered glucose metabolism, and abnormally high levels of fat in the blood [dyslipidemia],” Alexandre explained.

According to Paula Camila Ramírez, first author of the article, while these alterations are caused by weakness, “weakness is also caused by muscle alterations – loss of mass, infiltration of fat, and consequently inflammation. The muscles’ own metabolism is damaged, which in turn damages carbohydrate and lipid metabolism, as well as blood pressure control. These are all factors associated with metabolic syndrome.”

The inflammation caused by fat infiltration into muscles is only one piece of the jigsaw puzzle. An accumulation of fatty tissue is part of the natural aging process and can trigger chronic low-degree inflammation. Obesity on its own can cause permanent low-degree inflammation and metabolic alterations.

As the researchers noted, the alterations that characterize metabolic syndrome have traditionally been blamed on obesity. “However, there’s evidence that the problem is more complex, as shown by our study. Obesity and weak muscles contribute to weight gain and fat infiltration into the muscles. These two factors cause alterations to the metabolism of the musculoskeletal system and can influence other metabolic alterations,” Alexandre said.

In a previous study by the same research group, abdominal obesity and muscle weakness combined increased the risk of death from cardiovascular disease by 85% for the over-50s. Weakness alone increased this same risk by 62%. Curiously, the risk did not increase significantly for subjects with only abdominal fat.

“In that study, we focused on the impact of weakness combined with obesity on the incidence of cardiovascular disease. Here we set out to understand the mechanism involved. Our conclusion was that alterations in the muscular metabolism can contribute to a number of metabolic alterations, culminating in metabolic syndrome,” he said.

The article “Dynapenic abdominal obesity as a risk factor for metabolic syndrome in individual 50 years of age or older: English Longitudinal Study of Ageing” is at: www.sciencedirect.com/science/article/pii/S1279770724002148?via%3Dihub.