Scientists have found that fructose, a naturally occurring sugar, is a big cause of obesity. Fructose is also known as "fruit sugar". It is also processed to make high fructose corn syrup. This is a cause of obesity and is in a lot of the food we eat. A study from the University of Colorado found that although fructose isn't the biggest source of calories, it makes us want to eat fatty food. Researchers suggested we change what we eat. They said studies recognize the need to reduce junk food, but "it remains unclear whether the focus should be on reducing [fructose] intake".

The researchers conducted a study of all known causes of obesity. They found that the way our body converts fructose into energy causes lower levels of a compound called ATP. When ATP falls, we eat more. The lead researcher 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 believe that high amounts of fructose lead to health issues. The most common of these is non-alcoholic fatty liver disease.