The consumption of foods that claim to be lower in fat may actually lead to weight gain over time, new Irish research indicates.

According to the findings from the University of Ulster, foods that are marketed as ‘healthier' are sometimes seen by people as a license to overeat, resulting in eventual weight gain.

The research noted that when people eat products that claim, for example, to be low in fat or have reduced fat, they often eat portions that are larger than the recommended size.

They also often assume that these products are lower in calories than they actually are.

"There has been a huge increase in the number of food products with nutrition and health claims sold over the last 20 years, but we also know that the population's weight has continued to increase. We commissioned this research to explore people's understanding of these products given their popularity," explained Dr Cliodhna Foley-Nolan of Safefood, which funded the research.

It involved 180 adults nationwide. Each was shown three pairs of food, one marked as ‘healthier' and one marked as ‘standard'. They were asked to measure what they perceived to be a recommended portion of each food. They were also asked how guilty they would feel if they ate these foods.

The results showed that with five out of the six foods, the participants chose portion sizes that were 28-71% larger than the recommended portion size on the label.

According to lead researcher, Prof Barbara Livingstone, the findings support what is commonly referred to as the ‘health halo' effect.

"That is that consumers perceive these products to be healthier and with less calories than the ‘standard' version food. They see them as representing the less guilty option and so eat more of them. Further education on what is a healthy portion size is warranted to overcome these misconceptions," she explained.

Safefood noted that the overconsumption of just 50 calories per day can lead to a 5lb weight gain in a year.

Furthermore, the terms ‘reduced fat', ‘light' and ‘lite' simply refer to products that have 30% less fat than the standard original. However if the original was extremely high in fat to begin with, than even a ‘reduced fat' version may remain high in fat.

Details of the University of Ulster's study are published in the International Journal of Obesity.