Yale researchers say diet drinks could cause weight gain and upset metabolism

Jack Woodfield
Fri, 11 Aug 2017
Yale researchers say diet drinks could cause weight gain and upset metabolism
Consuming artificial sweeteners could be confusing the body which may lead to weight gain and trigger type 2 diabetes, American researchers have said.

A team at Yale University say bodies naturally associate sweetness with energy, but when we eat products which have been artificially sweetened and do not contain the amount of the calories the body expects, confusion can kick in.

Yale researchers believe low-calorie (or diet) beverages could trigger a "metabolic response" that leads to weight gain. However, this theory has been rejected by scientists at King's College London.

The Yale conclusions came from brain scans of 15 people when they drank diet and non-diet drinks, before monitoring how much energy was burned by the body.

A 'mismatch' was observed between sweetness and calories. With diet drinks, the body tastes sweetness without being offered calories. The researchers believe this may trigger a metabolic effect to store rather than burn energy even when no calories are present.

In nature, sweetness signals energy and the greater the sweetness the more calories are available, so the brain has evolved to expect the two to come together. When they do not, the brain can become confused, thinking there are fewer calories to burn.

The researchers say this upsets the body's natural metabolism and could explain previous research papers which have shown how diet products appear to raise blood sugar levels. They say the body links sweetness to high calories food and drink, and the sweetness and nutritional content do not marry up.

Dominic Dwyer, professor of psychology at Cardiff University, who wasn’t involved in the study, told the Daily Telegraph: "What the paper does imply, correctly in my view, is that mismatches between calories and sweetness interfere with metabolism of calories in a way that could have negative impact on weight gain, diabetes, heart disease etc, but that determining the link between the unprocessed calories and metabolic health needs future work."

The findings have been refuted by Tom Sanders, professor of Nutrition and Dietetics at King's College London.

Sanders said: "The claim is not supported by the observational evidence on people who are long-term consumers of artificial sweeteners. Furthermore, an analysis of trials of replacing sugar sweetened drinks with artificially flavoured drinks show that there is some weight loss. Weight gain is certainly is not caused by drinking artificial sweeteners."

The research was published in the journal Current Biology journal.
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