BLAME your belly on the sunshine, say scientists – as hot weather makes us gain weight.
A study in Australia estimated that someone’s risk of being obese increases by 0.2 per cent for every day of the year that is warmer than 30C.
Sweltering summer days might slow our metabolism by wrecking our sleep, put us off exercising, and have us reaching for fattening fizzy drinks to cool off.
The UK has enjoyed an early start to summer this year, with eleven 30C days so far.
The Met Office says 2025 is one of only three years on record to have had so many by July – with 2018 and 1976.
Research led by the University of Adelaide compared rates of obesity and weather across eight Australian states between 2006 and 2022.
It found citizens in the hottest areas were more likely to be obese and as an area’s temperatures increased so did the number of fat people.
Writing in the journal Economics & Human Biology, the study authors said: “High temperatures can make outdoor activities and physical activities less appealing, leading to a sedentary lifestyle which has been shown to increase obesity.
“Further, extreme temperatures can cause heat-related sleep disturbances that influence metabolism.
“Temperature shocks can also affect the body’s metabolism and appetite.
“High temperatures may suppress appetite in the short term, but can also lead to increased consumption of high-calorie, sugary beverages for cooling and hydration.”
Two thirds of British adults are overweight and about 30 per cent are obese, raising their risk of cancer, dementia and heart diseases.
The researchers suggested people in areas that are normally cold – such as the UK – might be more vulnerable.
They added: “We find that the effects of extreme temperature on obesity are more pronounced for people living in states with general cold climates and for older people compared to younger people.”
1
