Switching To Diet Soft Drinks Does Not Help People Lose Weight, Study Suggests

If you’re trying to lose weight you be be tempted to order a diet soft drink instead of a regular one. 

But a new study suggests making this common diet swap does not actually help people lose weight.

Researchers looked into the impact of non-nutritive sweeteners (NNS) such as stevia, monk fruit and aspartame, which are becoming increasingly popular in soft drinks.

They found that participants tended to eat more food after consuming NNS-based drinks, compared to regular sugar-based soft drinks. 

Researchers led by Siew Ling Tey, of the Agency for Science, Technology and Research in Singapore, tested the effect of four drinks on the body. 

One drink contained sugar (sucrose), another the artificial NNS aspartame and two others with natural NNS made from stevia or monk fruit plants. 

A group of 30 healthy male study participants randomly consumed one of the four sweetened drinks on each of the different days of the investigation.

On each test day, participants ate a standardised breakfast and by mid-morning received one beverage to tide them over until lunch.

An hour later they were provided with a lunchtime meal and asked to eat until comfortably full.

Their blood glucose and insulin concentrations were measured closely, while participants also kept a food diary of what they ate for the rest of the day.

The researchers described the findings as “surprising”. There was no difference in the total daily energy intake across all four drinks, meaning that overall participants consumed the same amount of energy (calories) during the course of a day.

They either reduced meal intake after the sugar-sweetened drink or ate significantly more at lunchtime and the rest of the day to compensate for the three calorie-free drink options.

The study found that although participants felt slightly hungrier and looked forward more to eating something again when they drank NNS beverages, they did not overindulge.

They did however eat more following the NNS drinks than when they consumed the sugar-sweetened drink.

“The energy ‘saved’ from replacing sugar with non-nutritive sweetener was fully compensated for at subsequent meals in the current study, hence no difference in total daily energy intake was found between the four treatments,” Tey explained.

“It appears that the source of non-nutritive sweeteners, whether artificial or natural, does not differ in its effects on energy intake, postprandial glucose and insulin.”

The study is published in the International Journal of Obesity.