SOME low-fat supermarket products – several of which are on sale here – contain more calories than the food's ordinary full-fat version.
Most low-fat products have a third fewer calories, yet one in 10 had more or the same calories than alternatives.
A study which will be presented to a major conference on obesity today mostly looked at products in UK-based supermarket chains such as Sainsbury's and Asda but some of the products are on sale in Irish stores such as Tesco.
For instance Birdseye light and crunchy breaded chicken had more calories than Birdseye crispy chicken. Weight Watchers wholemeal thick slice bread had more calories than the Tesco own label product.
Weight Watchers sliced cheese also has more calories than any own brand sliced cheese, the findings presented to the European Congress on Obesity reveals.
The study, carried out by researchers including Dr Matthew Capehorn, Rotherham Institute for Obesity in the UK, set out to establish whether these low-fat versions were nutritionally healthier, mainly in terms of sugar and overall calories.
The researchers analysed the fat, sugar and calorie content for any low-fat food that had a directly comparable regular fat product made by the same brand.
In the case of 62 products found in four supermarkets, some 56 low-fat products had fewer calories.
And overall the low-fat products had on average 31pc less calories.
However, 10pc of low-fat foods analysed still had more or the same calories than the regular fat version.
One low fat product, Asda own brand low-fat Italian dressing, had more fat than the regular fat alternative.
The authors advised: "Low-fat foods do appear on average to help reduce calorie intake and therefore may be encouraged as part of a weight loss strategy.
"However, appropriate food choices may still require reading nutritional information on the food labels as 10pc of low-fat foods still have more calories, and 40pc have more sugar, than their regular fat counterparts."
A separate study presented to the congress in Sofia, Bulgaria, shows that people who eat two or more portions of white bread per day are at a 40pc increased risk of becoming overweight or obese compared with those who eat less than one portion per week.
No statistically significant association was observed between wholegrain bread only and overweight and obesity.
The nature of the carbohydrates, fibre content, and other micronutrients in wholegrain bread may explain the lack of association between obesity and wholegrain bread consumption.
"Consumption of white bread of two portions per day or more showed a significant direct association with the risk of becoming overweight or obese," they added.