Scientists have discovered why people don’t find fruit salads very filling for their stomach.

Researchers from the University of Southern California found that a naturally occurring sugar in fruit, fructose, leaves people hungrier.

Twenty-four volunteers were viewed images of high-calorie foods and non-food items while ingesting either fructose or glucose.

The volunteers were then asked to rate their hunger and desire for food.

The researchers found that those who had ingested fructose had greater hunger levels than those who ate glucose.

The researchers said that their findings suggest that “ingestion of fructose relative to glucose results in greater activation of brain regions involved in attention and reward processing and may promote feeding behaviour”.

Fructose is commonly found in fruits and vegetables, while glucose can be found in major carbohydrates such as starch.

Even though fructose and glucose have the similar calorific value, they are both processed differently by the body.

The Telegraph states that calls in the body regulate the around of glucose found in order to make energy.

Fructose, on the other hand,  is metabolized in the liver and causes seven times as much cell damage as glucose.

Researchers added that the increasing levels of fructose in some diets could be could be contributing to growling levels of obesity, as fructose is often used in sweeteners.

They wrote that, “Obesity is a major public health problem, and increases in the consumption of fructose may be an important contributor to the current obesity epidemic.”

Melanie Brown, Nutritional therapist advises eating “no more than 15g of fructose” per day and to avoid fruit juices and dried fruit.