Eating disorders may have a stronger biological component than previously understood, with new research suggesting that genetic factors linked to binge eating and anorexia nervosa are distinct from those that influence body weight.

Researchers at Sweden’s Karolinska Institutet examined genetic information from thousands of people to investigate factors associated with eating disorder behaviours. Their findings suggest that these conditions cannot be explained solely by body image, weight or metabolism.

The study, published in Nature Mental Health, included nearly 40,000 people with binge-eating behaviour and about 25,000 people with anorexia nervosa. Researchers compared them with more than 1.2 million people without eating disorders.

The team identified genetic variations statistically associated with a greater likelihood of developing the conditions. Six genetic markers were linked to binge eating, while eight were associated with anorexia nervosa. Two of the markers connected to anorexia had not previously been identified.

Lu Yi, principal researcher at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics, said the findings showed that eating disorders were not simply related to body weight.

The researchers noted that many genetic variants associated with eating disorders differ from those that influence how much a person weighs. This points to a more complicated biological basis for the conditions.

Scientists can combine the effects of multiple genetic markers to produce what is known as a polygenic risk score. Such a score reflects the number and strength of genetic variants associated with a particular condition.

However, the researchers stressed that these genetic markers remain weak predictors when used on their own. Other biological, psychological and environmental factors would need to be considered when assessing an individual’s risk.

The study also identified links between genetic markers associated with eating disorders and other health and behavioural characteristics.

Some genetic markers connected to binge eating were also associated with traits involving impulse control, including smoking and risk-taking behaviour. They were also linked to higher body mass index and attention-deficit hyperactivity disorder.

Anorexia-related markers showed stronger genetic associations with obsessive-compulsive disorder.

The researchers said these differences suggest that binge eating and anorexia nervosa may involve partly separate biological mechanisms, even though both are classified as eating disorders.

Lisa Dinkler, an assistant professor at Karolinska Institutet, said the findings could eventually contribute to more targeted treatment approaches based on the specific characteristics of different eating disorders.

Eating disorders affect millions of people worldwide and are associated with serious risks to physical and mental health. They commonly involve disturbed eating patterns, intense concerns about food, weight or body shape, and significant effects on daily functioning.

Researchers said the findings could help shift the understanding of eating disorders away from a narrow focus on body weight and toward a broader view that considers distinct biological pathways.

US scientists have examined the biological processes behind five widely used ageing tests, finding that different methods appear to capture different aspects of how the human body ages.

Researchers analysed blood samples from 3,227 people who took part in the US Health and Retirement Study. They compared five commonly used epigenetic clocks with patterns of gene activity in the participants’ blood to determine what biological changes were associated with faster ageing according to each test.

Epigenetic clocks are mathematical tools that estimate biological age using DNA methylation, chemical changes that can influence how genes function without altering the underlying genetic code.

Scientists have increasingly used these clocks to investigate links between biological ageing, disease, physical decline and the risk of death. However, researchers have not always known precisely what processes inside the body were being reflected when a clock indicated that someone was ageing faster than expected.

The new study found that the five clocks were associated with different molecular signs of ageing. Some were more strongly connected to processes involved in energy use and cell growth, while others showed stronger links to immune activity and inflammation.

Despite those differences, the clocks shared several biological features. These included changes involving the immune system, metabolism and communication between cells.

The findings could help researchers select the most appropriate biological ageing test for a particular study. A clock associated more closely with immune activity, for example, could be more useful for research into immune-related ageing than one that primarily reflects metabolic changes.

The researchers also developed new measures called transcriptomic ageing gene scores, or TAGS, based on the molecular patterns identified in their analysis.

According to the study, TAGS in several cases performed better than the ageing clocks alone when predicting health outcomes. These included frailty, walking speed, heart disease, diabetes, lung disease and mortality.

T. Em Arpawong, a research associate professor at the USC Leonard Davis School of Gerontology, said ageing is not determined simply by chronological age but also by biological changes taking place inside cells.

Senior author Eileen Crimmins said the study helps explain what is happening beneath the surface when biological ageing tests produce their results.

By identifying the molecular processes associated with individual ageing clocks, researchers may be able to interpret their readings more accurately and understand which tools are best suited to different areas of ageing research.

The findings could eventually support research into preventing age-related illness and identifying people at higher risk of declining health. However, the study focuses on biological markers and does not mean the new measures are ready to replace clinical assessments of health or provide individual predictions of lifespan.

Researchers said the work provides a clearer picture of the biological mechanisms captured by ageing clocks and could guide their use in future studies of ageing and disease.