Does Diet Soda Make You Fat?

The Internet has helped rumors about aspartame become more exaggerated—it's been said to cause seizures, lupus, autism, Gulf War syndrome (huh?) and more. But researchers from School of Medicine at the University of Texas Health Science Center San Antonio report that diet soda with aspartame causes health problems unrelated to chain emails. Consuming aspartame is linked to increased waistlines, which contributes to a host of medical problems. Longtime aspartame consumption also contributes to insulin resistance.

Researchers from San Antonio Health Science Center looked at data from 474 participants in the San Antonio Longitudinal Study of Aging (SALSA).

When subjects enrolled in SALSA, researchers recorded their height, weight, waist circumference, and diet soda intake. Over the next decade, researchers conducted follow-up exams and compared diet soda drinkers to non-diet soda drinkers. Diet soda drinkers saw a 70 percent increase in waist circumference (compared to non-diet soda drinkers). Users who consumed two or more diet sodas a day saw their waistlines increase 500 percent more than the non-diet soft drinking group. Excessive abdominal fat correlates with a higher risk of diabetes and also increases the chances of diseases such as colorectal cancer or high blood pressure.

"These results suggest that, amidst the national drive to reduce consumption of sugar-sweetened drinks, policies that would promote the consumption of diet soft drinks may have unintended deleterious effects," the researchers wrote. They presented their findings at the American Diabetes Association's Scientific Sessions.

In a separate study, researchers looked at how aspartame influenced mice’s fasting glucose levels. Typically, a person’s glucose level is lowest after eight hours of fasting and doctors sometimes test the amount of glucose in the blood at this time to determine diabetes. The researchers, also from San Antonio, fed two groups of mice chow—both varieties included corn oil, but one had aspartame. After three months of guzzling sweetened, fatty chow, the mice in the aspartame group showed increased level of fasting blood glucose and diminished insulin levels, which indicates early decline in pancreatic beta cell function. Beta cells produce insulin, which naturally regulates blood glucose. Faulty beta cells negatively impacts insulin production, leading to Type II diabetes.