A commonly-used pesticide could be partially responsible for the global obesity epidemic, finds a study.
Researchers from McMaster University in Canada discovered that chlorpyrifos -- widely sprayed on fruits and vegetables in many parts of the world -- slows down the burning of calories in the brown adipose tissue of mice.
Reducing the burning of calories, a process known as diet-induced thermogenesis, causes the body to store these extra calories and promotes obesity.
Scientists made the discovery after studying 34 commonly used pesticides and herbicides in brown fat cells and testing the effects of chlorpyrifos in mice fed high calorie diets.
The findings published in the journal, 'Nature Communications', can have important implications for public health.
"Brown fat is the metabolic furnace in our body, burning calories, unlike normal fat that is used to store them. This generates heat and prevents calories from being deposited on our bodies as normal white fat. We know brown fat is activated during cold and when we eat," said Gregory Steinberg, Professor of medicine at McMaster.
"Lifestyle changes around diet and exercise rarely lead to sustained weight loss. We think part of the problem may be this intrinsic dialling back of the metabolic furnace by chlorpyrifos," he added.
Steinberg said chlorpyrifos would only need to inhibit energy use in brown fat by 40 calories every day to trigger obesity in adults, which would translate to an extra five lbs (pounds) of weight gain per year.
He further said that while several environmental toxins including chlorpyrifos have been linked to rising obesity rates in both humans and animals, most of these studies have attributed weight gain to increases in food intake and not the burning of calories.
Obesity is responsible for 4.7 million premature deaths each year.
It is a risk factor for several of the world's leading causes of death, including heart disease, stroke, diabetes and various types of cancer.