Non-food perks with smaller food portions could significantly counter the rising problem of obesity, researchers find.

Eating smaller portion sizes and adding a non-food prize can help cut back on overeating, scientists say.

Researchers have found that swapping extra food at mealtimes with other perks, such as toys, games and even lottery tickets, leaves people just as satisfied as finishing off a large plateful of comfort food.

The idea, say the experts from the University of Arizona and the University of South Carolina, could be used to significantly counter the rising problem of obesity.

The study revealed most children and adults chose a half-sized portion paired with a toy or monetary prize over a full-sized portion without extra incentives.

Even if the subjects were particularly hungry, they still opted for the smaller food option and did not feel the need to eat more later on.

Alongside the experiments, the researchers used functional magnetic resonance imaging (fMRI), which showed both options activated the same areas of the brain responsible for controlling reward, desire and motivation.

In their report, Can Smaller Meals Make You Happy? Behavioural, Neurophysiological And Psychological Insights Into Motivating Smaller Portion Choice, they wrote: "Clearly, eating less is not fun for many people (and may even be a source of short-term unhappiness), as portion size restriction requires discipline and self-control.

"Yet, by combining one shorter-term desire (to eat) with another shorter-term desire (to play) that in combination also address a longer-term desire (to be healthy), different sources of happiness become commensurable."

They also pointed out that adult participants even preferred to gamble on the chance of a prize, opting for the vague possibility of a win over being given precise odds. For example, participants were more drawn in by adverts saying they "could win" frequent-flyer miles, than by those listing the exact odds of winning.

Research Martin Reimann said: "One explanation for this finding is that possible premiums may be more emotionally evocative than certainty premiums.

"This emotional evocation is clearly present in gambling or sports contexts, where the uncertainty of winning provides added attraction and desirability through emotional 'rushes' and 'thrills'."

The concept could lead to a general reduction in people's calorie intake by encouraging them to get into the habit of celebrating and rewarding their own achievements with tempting non-food items.

The report added: "Similarly, we recommend that parents could reward and, thus, reinforce their children's achievements with non-food incentives, even uncertain ones, rather than with food.

"As such, parents lessen the likelihood of linking good behaviour to food intake, but instead link good behaviour to the receipt of a non-food incentive and, thus, avoid overeating."