Pollution from car exhausts and trendy wood-burning stoves could be making you fat.
Scientists say being exposed to the toxic air particles which come from traffic fumes, heavy industry and wood burning in homes and gardens may cause people to put on weight.
A study of more than four million people worldwide, including in the UK, found those who lived in areas with high levels of air pollution were more likely to be obese, have bigger waist measurements and carry more abdominal fat – the ‘spare tyre’ which is linked to heart disease and type 2 diabetes.
Air pollution has long been linked to a range of chronic diseases, from dementia to asthma, heart problems and cancer.
But the latest study by Canadian researchers is the first to look at the links to obesity.
It is thought breathing in polluted air allows hazardous microscopic particles known as PM2.5 and PM10 to penetrate deep into the lungs and the bloodstream, triggering long-term inflammation in the body.
This in turn may slow the body’s metabolism, triggering it to store more fat, and making it less efficient at processing sugar – resulting in weight gain.
It means that air pollution could cause people to pile on the pounds even if their eating habits don’t change.
Scientists say wood burning in homes and gardens may cause people to put on weight (file photo)
The researchers, from McMaster University in Ontario found exposure to higher levels of PM2.5 was associated with an extra 1.2cm on the waist, a one-unit increase in BMI measurement and a 1.6 per cent increase in waist-to-hip ratio.
Each increase in PM2.5 and nitrogen dioxide, another pollutant, was also associated with weight gain.
Writing about their research in the journal Environmental Research, the scientists said: ‘Higher PM2.5 and nitrogen dioxide concentrations were associated with increased BMI, waist circumference, waist-to-hip ratio, and greater odds of general and abdominal obesity.’
A report by the Royal College of Physicians earlier this year found that air pollution affects every organ in the body and may be linked to 30,000 deaths a year in the UK.