Obesity can have severe effects on a person’s quality of life and lifespan. Research shows that it substantially increases the risk of a wide range of diseases, including type 2 diabetes, cardiovascular disease, and some cancers.

Despite the long-established health risks, however, recent decades have seen an inexorable rise in rates of obesity throughout the world.

One study found that between 1980 and 2015, the prevalence of obesity doubled in more than 70 countries and steadily increased in most others.

According to the World Health Organization (WHO), in 2016, more than 650 million adults had obesity. Overweight and obesity now claim the lives of more than 2.8 million people each year.

A major challenge for researchers is to distinguish the effects of genetics from those of lifestyle on the progression of obesity and its effects on health.

A team of researchers, led by two from the Obesity Research Unit at the University of Helsinki, in Finland, used an ingenious way to do this.

By studying 49 pairs of identical twins who did not share the same body mass index, or BMI, readings, they removed the effect of genes from the equation.

Identical, or monozygotic, twins have the same genetic makeup. They experience almost identical conditions in the womb and usually have very similar upbringings.

This means that the differences between the twins in the study arose from the influence of their environment or lifestyle as adults, rather than their genes or conditions during childhood.

The researchers have published their findings in the journal Cell Reports Medicine.

Biopsies of fat and muscle

First, the researchers took blood samples and biopsies of fat, or adipose, tissue and skeletal muscle tissue from the volunteers.

They then used a variety of molecular techniques to analyze the transcription of genes, production of proteins, and processing of metabolites in the two types of tissue.

A key finding was that the activity of mitochondria, the power plants of cells, was reduced in the muscle and adipose tissue of people with obesity.

The change was more marked in adipose than in muscle tissue.

Meanwhile, there was also increased inflammation in the tissues from twins with obesity, compared with their leaner siblings.

The changes in adipose tissue, but not muscle tissue, were associated with adverse health effects, including fatty liver disease and insulin resistance, conditions that have been linked to the development of diabetes.

Medical reference: Medical News Today