A team of Massachusetts General Hospital (MGH) scientists has found a possible mechanism explaining why use of the sugar substitute (aspartame) might not help with weight loss.
In their report published online in Applied Physiology, Nutrition and Metabolism, the researchers show how the sugar substitute interferes with the action of an enzyme previously shown to prevent metabolic syndrome — a group of symptoms associated with type 2 diabetes and cardiovascular disease.
They also showed that mice receiving sugar substitute in their drinking water gained more weight and developed other symptoms of metabolic syndrome than animals fed similar diets lacking aspartame.
“Sugar substitutes like aspartame are designed to promote weight loss and decrease the incidence of metabolic syndrome, but a number of clinical and epidemiologic studies have suggested that these products don’t work very well and may actually make things worse,” says Richard Hodin, MD, of the MGH Department of Surgery, the study’s senior author.
“We found that the sugar substitute blocks a gut enzyme that can prevent obesity, diabetes and metabolic syndrome; so we think that aspartame might not work because, even as it is substituting for sugar, it blocks the beneficial aspects of the enzyme.”
To better represent the effects of consuming beverages or other products containing sugar substitute, the researchers followed four groups of mice for 18 weeks.
Two groups were fed a normal diet, one receiving drinking water with aspartame, and the other receiving plain water.
The other two groups were fed a high-fat diet, along with either sugar substitute-infused or plain water.
Animals in the normal diet group that received sugar substitute consumed an amount equivalent to an adult human’s drinking about three and a half cans of diet soda daily, and sugar substitute-receiving animals in the high-fat group consumed the equivalent of almost two cans.
At the end of the study period, while there was little difference between the weights of the two groups fed a normal diet, mice on a high-fat diet that received aspartame gained more weight than did those on the same diet that received plain water.
Sugar substitute-receiving mice in both diet groups had higher blood sugar levels than did those fed the same diets without sugar substitute.
“People do not really understand why these artificial sweeteners don’t work.
“There has been some evidence that they actually can make you more hungry and may be associated with increased calorie consumption.”
“Our findings regarding sugar substitute may help explain why the use of aspartame is counterproductive,” says Hodin, who is a professor of Surgery at Harvard Medical School.
“While we can’t rule out other contributing mechanisms, our experiments clearly show that the sugar substitute blocks IAP enzyme activity, independent of other effects.”