SCOTLAND’S obesity epidemic is being fuelled by a Homer Simpson generation of thirty-something couch potatoes.

A new study monitoring the weight of 1,000 Scots over a decade has found that people in their late 30s are piling on more pounds than those in their late 50s.

According to researchers, the lifestyle embodied by the star of the Simpsons cartoon series — a doughnut and beer-loving 38-year-old father-of-three — is to blame.

Nutritionists highlight comfort eating as a response to the stress of parenthood, long working hours and moving home. They also point to a misguided sense of immortality among thirtysomethings, who are ignoring healthy lifestyle messages and spending long periods in front of the TV eating junk food and drinking.

This contrasts with people approaching retirement, who are more likely to eat healthily and take exercise.

On average, men and women in their late 30s put on 5.5kg over the period of the study, compared with just 1.8kg among the over-50s.

The average weight of younger men rose 7% from 78kg to 83.5kg and from 64.5kg to 70kg among women, a rise of 8.5%.

Overall, more than 42% of participants experienced a “major” weight gain greater than 5kg and almost a fifth put on more than 10kg over the duration of the study.

The proportion who were overweight or obese rose from 54.9% to almost 70%. Only 20% of subjects maintained a stable weight for the duration of the study.

“Younger people are gaining weight more rapidly,” said Mike Lean, professor of nutrition at Glasgow university and co-author of the report, published in the current edition of the European Journal of Clinical Nutrition.

“Changing jobs, getting married and moving home are all stressful but there’s also the possibility that young people do not care about their weight.”

The study, conducted by academics in Scotland, Iran and Australia, also warns that, contrary to popular belief, “insidious” weight gain is common across the social classes.

This challenges the current focus of healthy eating campaigns on deprived areas.

Instead, the research recommends all social groups need to be targeted, particularly those in their 30s and 40s.

“This study shows that only a fifth of Scots maintain their weight over the long-term,” said Dr Carrie Ruxton, an independent dietitian. “Younger people are gaining more weight than older people, perhaps due to inactivity and binge drinking.

The study, which monitored the weight of volunteers in Glasgow between 1991 and 2000, used the occupation of the main breadwinner in each household to determine social status. The height, weight, waist circumference and body mass index for each participant was measured three times over the period.

The proportion of overweight and obese people in Scotland is second only to America. Around a third of Scottish children are overweight and a quarter of adult men qualify as obese, together with a fifth of women.

Across the UK, obesity costs the economy around £7 billion a year in treatment, benefits, loss of earnings and reduced productivity. This figure, if left unchecked, is predicted to rise to £60 billion by 2050.

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