Aspartame To Blame! Diet Soda Really Might Cause Weight Gain, Researcher Says

Aspartame, the sugar substitute used in some diet sodas, is often consumed by people trying to lose weight, but new research suggests, as many skeptics have before, that aspartame might actually cause people to gain weight. Previous research has indicated that even acceptable daily intake amounts, as regulated by the United States Food and Drug Administration (FDA), might make people feel hungrier and eat more. Now, a team of researchers from the Massachusetts General Hospital have disclosed their findings as to why aspartame does not promote weight loss. The research was published in the journal Applied Physiology, Nutrition and Metabolism. The team claims that one of aspartame’s metabolites might be the culprit. The researcher team was led by Dr. Richard Hodin from the Massachusetts General Hospital Department of Surgery.

A breakdown product of aspartame is phenylalanine. It inhibits a gut enzyme called intestinal alkaline phosphatase (IAP). This enzyme has been shown to prevent metabolic syndrome in rodents, according to Medical News Today. Metabolic syndrome is a group of symptoms associated with type 2 diabetes, cardiovascular disease, and obesity. The Inquisitr reported earlier this year that diet soda consumption might increase the risk of type 2 diabetes. Now, researchers say that diet soda might even cause weight gain.


Dr. Hodin and team already had shown that IAP can prevent the onset of metabolic syndrome. Based on that earlier research, the team hypothesized that consuming aspartame might promote metabolic syndrome and cause weight gain. The research was conducted on mice by adding aspartame to diet and regular soda, and then measuring IAP activity in the rodents. They used four groups of mice. Two of the groups were put on a normal diet, but one group received drinking water with aspartame and the other group was given just plain water. The other two groups of mice were put on high-fat diets. Again, one group received drinking water with aspartame and the other group was given just plain water. The groups that were put on a normal diet were consuming the equivalent of three-and-one-half cans of diet soda for humans every day and the rodents that were on the high-fat diets were consuming aspartame equivalent of almost two cans of diet soda for humans every day. The mice were then monitored for 18 weeks.


“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,” Dr. Hodin said. “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.”

The press release said that the researchers’ findings “clearly show that aspartame blocks IAP activity, independent of other effects.”

“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. Aspartame-receiving mice in both diet groups had higher blood sugar levels than did those fed the same diets without aspartame, which indicates glucose intolerance, and both aspartame-receiving groups had higher levels of the inflammatory protein TNF-alpha in their blood, which suggests the kind of systemic inflammation associated with metabolic syndrome.”

The study concluded that endogenous IAP’s protective effects in preventing metabolic syndrome might be inhibited by the suspected metabolite of aspartame, but Dr. Hodin went so far as to call aspartame counterproductive to weight loss diets.


In October, the Inquisitr reported that a leaked email from a former head of the FDA indicated that American politician and businessman Donald Rumsfeld has a lot to answer for due to his part in the approval of Nutrasweet, the controversial artificial sweetener made from aspartame.

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