Eating ultra-processed foods like breakfast cereals and ready meals is linked to more fat being stored in the thighs regardless of how many calories are consumed, new research suggests.

The study also found that diets high in ultra-processed foods also impacted muscle quality regardless of how much exercise someone did.

Experts say higher amounts of fat in the thigh muscle could increase the risk for knee osteoarthritis.

Study author Zehra Akkaya, researcher and former Fulbright Scholar in the Department of Radiology and Biomedical Imaging at the University of California, San Francisco, US, said: “The novelty of this study is that it investigates the impact of diet quality, specifically the role of ultra-processed foods in relation to intramuscular fat in the thigh muscles assessed by MRI.

“This is the first imaging study looking into the relationship between MRI-based skeletal muscle quality and quality of diet.”

Ultra-processed foods, which includes things like frozen pizzas, fizzy drinks and margarine, usually have longer shelf lives and are highly appealing, as they are convenient and contain a combination of sugar, fat, salt and carbohydrates.

These ingredients affect the brain’s reward system, making it hard to stop eating.

In the new study, presented at the annual meeting of the Radiological Society of North America, researchers set out to assess the association of ultra-processed food intake and their relationship to fat in the thigh muscle.

The researchers analysed data from 666 people who took part in the Osteoarthritis Initiative in the US, a nationwide research study that helps researchers better understand how to prevent and treat knee osteoarthritis.

The study found that the more ultra-processed foods people consumed, the more fat they had in their thigh muscles, regardless of how many calories they ate.

Dr Akkaya said: “In an adult population at risk for but without knee or hip osteoarthritis, consuming ultra-processed foods is linked to increased fat within the thigh muscles.

“These findings held true regardless of dietary energy content, BMI, sociodemographic factors or physical activity levels.”

“Targeting modifiable lifestyle factors, mainly prevention of obesity via a healthy, balanced diet and adequate exercise, has been the mainstay of initial management for knee osteoarthritis.”

“Osteoarthritis is an increasingly prevalent and costly global health issue.

“It is the largest contributor to non-cancer related health care costs in the US and around the world.

“Since this condition is highly linked to obesity and unhealthy lifestyle choices, there are potential avenues for lifestyle modification and disease management,” Dr Akkaya added.