Diet-beverage consumers tend to compensate for the absence of calories in their drinks by noshing on extra food that is loaded with sugar, sodium, fat and cholesterol, the study said.
“If people simply substitute diet beverages for sugar-sweetened beverages, it may not have the intended effect because they may just eat those calories rather than drink them,” said researcher Ruopeng An, professor at University of Illinois in the US.
Switching to diet or sugar-free drinks may not help people control their weight if they do not pay attention to the quantity and quality of the foods they consume, An said.
The study examined the dietary habits of more than 22,000 US adults.
An compared participants’ daily calorie intakes, including their consumption of energy-dense but nutrient-poor discretionary foods that include products such as cookies, ice cream, chocolate, fries and pastries, and five types of beverages — diet drinks, sugar-sweetened beverages such as sodas and fruit drinks, coffee, tea and alcohol.
While coffee and diet-beverage drinkers consumed fewer total calories each day than people who preferred alcohol or sugary drinks, they obtained a greater percentage of their daily calorie intake from discretionary foods, An said.
“It may be that people who consume diet beverages feel justified in eating more, so they reach for a muffin or a bag of chips,” An said.
“Or perhaps, in order to feel satisfied, they feel compelled to eat more of these high-calorie foods,” he said.
A third possible explanation might be that people opt to drink diet beverages because they feel guilty about indulging in unhealthy food, An said.
“It may be one – or a mix of – these mechanisms,” he pointed out.
The findings will be published in a forthcoming issue of the Journal of the Academy of Nutrition and Dietetics.