Lead researcher Professor Barbara Livingstone, of the University of Ulster, said consumers were being influenced by the “health halo” of some products.
For example, with a lower fat coleslaw they’ll eat as much as 126g of it compared with just 74g of a luxury brand. The same applied to breakfast cereal with women choosing larger portions of Special K than Frosties, researchers found. This means buying “healthier” products could actually lead to weight gain over time she said
“They see them as representing the less guilty option and so eat more. Further education on what is a healthy portion size is warranted to overcome these misconceptions,” she said.
The research, which was carried out among 180 adults and published in the ‘International Journal of Obesity’, found that people selected portion sizes that were between 28pc and 71pc larger than what was recommended in five out of six cases.
Dr Foley-Nolan said there had been a huge increase in the number of foods with nutrition and health claims over the past 20 years but the population was still getting fatter.
“The research shows that these foods are viewed by some consumers as a licence to overeat,” Dr Foley-Nolan added.
“However, in the case of many products, the fat that is removed in the ‘healthier’ product is replaced by other ingredients, such as sugar, and the calorie savings are small.”