Scientists have discovered that fructose, a naturally occurring sugar, is a major driver of obesity. Fructose is also known as "fruit sugar". It occurs to varying degrees in fruit and vegetables. It is also used in processed form in high fructose corn syrup, which is in a lot of the food we eat, and promotes obesity. A study led by Dr Richard Johnson at the University of Colorado found that although fructose isn't the biggest source of calorific intake, it stimulates an urge to eat fattier food. Researchers posited a shift of focus on what we eat. They wrote: "All hypotheses recognize the importance of reducing 'junk' foods, [however] it remains unclear whether the focus should be on reducing [fructose] intake."

Dr Johnson and his colleagues conducted an exhaustive study of all known contributors to obesity. They found that the process of our body converting fructose into energy causes a drop in the levels of a compound called ATP. When ATP falls, our body tells us to eat more. Researchers call this process the fructose survival hypothesis. Johnson said: "Fructose is what triggers our metabolism to go into low power mode and lose our control of appetite, but fatty foods become the major source of calories that drive weight gain." Scientists have attributed the consumption of high amounts of fructose to health issues. The most common of these is non-alcoholic fatty liver disease.