Diet drinks have been in the last decades seen as a substitute for regular sugary drinks as a result of their low-calorie content. However, recent studies have shown that diet soda may not be that effective for people who are trying to shift the pounds. Aspartame sweetener used in most diet drinks in lieu of sugar has been found to prevent weight loss by blocking intestinal enzyme’s activity.

Scientists at Massachusetts General Hospital (MGH) say it’s all to do with sugar substitutes aspartame and found a possible explanation to why the use of the sugar substitute aspartame might not promote weight loss.

"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," said Dr Richard Hodin, MD, of the MGH Department of Surgery, the lead author of the study published in online in A Applied Physiology, Nutrition and Metabolism.

"We found that aspartame blocks a gut enzyme called intestinal alkaline phosphatase (IAP) that we previously showed 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 IAP."

"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 aspartame's inhibition of IAP may help explain why the use of aspartame is counterproductive," says Hodin, who is a professor of Surgery at Harvard Medical School.

You can read more on the study here if you are interested
http://www.humantherapyhub.com/2016/11/diet-drinks-may-prevent-weight-loss.html

dominique