Diet drinks could make you put on weight

DIET drinks or foods may actually prevent weight loss and trigger diabetes because the brain misreads the number of calories present and reduces metabolism, a study suggests.

Researchers at Yale University in the US discovered that the body stops burning energy from food if there is a “mismatch” between food sweetness and calories.

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 and thinks there are fewer calories to burn.

The scientists say the findings could help explain previous studies that have suggested that artificial sweeteners can increase blood sugar levels and possibly trigger diabetes.

“A calorie is not a calorie,” said senior author Dana Small, professor of psychiatry at Yale University School of Medicine. “Calories are only half of the equation; sweet taste perception is the other half.

“When sweet taste and energy are not matched, less energy is metabolised and weaker, or inaccurate, signals are sent to the brain. Either one of these effects may affect metabolic health.”

For the study, published in the journal Current Biology, scientists scanned the brains of 15 people when they were drinking diet drinks, and compared them with drinking regular beverages. They also monitored how much energy was burned by the body.

They found that when there was a “mismatch” between sweetness and calories the calories fail to trigger the body’s metabolism. Reward circuits in the brain did not register that calories

had been consumed, which could lead to eating more.

Commenting on the paper, Dominic Dwyer, professor of psychology at Cardiff University, said: “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.”

However, other British experts were more sceptical. Naveed Sattar, professor of metabolic medicine at Glasgow University, said: “There is currently no strong evidence that diet drinks are necessarily bad for you, whereas there is stronger and consistent evidence for sugar sweetened drinks being linked to higher diabetes risk.”

Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, added: “The statement that a calorie is not a calorie is gobbledegook… The remark is as stupid as saying a pound of feathers is lighter than a pound of lead.

“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.”

Tam Fry of the National Obesity Forum added: “This research should be enough to convince you that artificial ingredients, whether they be in food or drink, can screw up your system even though they may sound healthy.

“They may be free of calories but not of consequences and diabetes is only one of them.”