"People think (healthier food) is lower in calories," said Pierre Chandon, a marketing professor at the INSEAD Social Science Research Center in France, and they "tend to consume more of it."
That misconception can lead to people eating larger portion sizes of so-called healthy foods, and therefore more calories.
"Foods are marketed as being healthier for a reason, because food producers believe, and they correctly believe, that those labels will influence us to eat their products and perhaps eat more of their products," said Dr. Cliodhna Foley Nolan the director of Human Health and Nutrition at Safefood, a government agency in Ireland.
Safefood commissioned the study, led by Barbara Livingstone, a professor at the University of Ulster.
Foley Nolan said that the portion sizes of food have become larger over the years, and Safefood wanted to see whether health and nutrition claims had any influence.
The researchers asked 186 adults to assess the appropriate portion sizes of foods.
Given a bowl of coleslaw, the participants served themselves more of the coleslaw labeled "healthier" than the coleslaw labeled "standard."
For instance, obese men served themselves 103 grams of healthy coleslaw and 86 grams of standard coleslaw.
In reality, the healthy-labeled coleslaw had just as many calories - 941 kilojoules (or 224 calories) for every 100 grams - as the "standard" coleslaw, which had 937 kilojoules (or 223 calories).
Additionally, people tended to underestimate how many calories were in a serving for the "healthier" coleslaw.
The participants most often thought the "healthier" coleslaw contained 477 kilojoules, or 113 calories.
In contrast, they were not far off in estimating the calories in the "standard" coleslaw.
‘A CERTAIN LICENSE TO OVEREAT'
Chandon, who was not part of this study, said people tend to stereotype food that might be healthy in one aspect, say, lower in fat, as being healthy in every dimension.
But in fact, food labeled as being healthy is not always lower in calories.
He said one reason why people might overeat healthier foods is because they feel less guilt when they choose a healthier option.
"We think that these kinds of marketing means…of labeling things as being healthier, that it gives us a certain license to overeat and it can be dangerous" with regard to weight gain, Foley Nolan said.
She said the findings will be useful in developing nutrition policies and education campaigns to help people make healthy food choices.
Foley Nolan recommended that people bulk up on fruit and vegetables, rather than processed foods, even if they are labeled as healthy.
Chandon added that shoppers should also look at nutrition labels and calorie content.
"Just pay attention to those (health) claims and don't generalize or stereotype on one (type of) nutritional information," he said.
