WHY YOU SHOULD AVOID ASPARTAME. I've always preferred Sweet-N-Low to NutraSweet:
Why does aspartame not aid weight loss? "We found that aspartame blocks a gut enzyme called intestinal alkaline phosphatase (IAP)," explains Professor Hodin, who teaches at Harvard Medical School.
IAP is produced in the small intestine. "We previously showed [this enzyme] can prevent obesity, diabetes and metabolic syndrome [a disease characterized by a combination of obesity, high blood pressure, a metabolic disorder and insulin resistence]. So, we think that aspartame might not work because, even as it is substituting for sugar, it blocks the beneficial aspects of IAP."
However, aspartame does not block the enzyme directly. It does so through one of its intestinal breakdown products called phenylalanine.