June 29, 2011

Diet Sodas May Actually Expand Waistlines

People who drink diet sodas in an attempt to shed pounds or avert weight gain may be inadvertently sabotaging their goals, according to two University of Texas studies presented June 25 and 27 at a meeting of the American Diabetes Association in San Diego.

In the first study, epidemiologists at the University of Texas Health Science Center in San Antonio found that people who drank two or more diet sodas each day grew their waist size six times as much as those who abstained from diet drinks.

"Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised," warned Dr. Helen Hazuda, senior author of the study and professor and chief of the Division of Clinical Epidemiology of the Texas University School of Medicine.

"They may be free of calories but not of consequences," she said.

The decade-long study assessed data from 474 participants of the San Antonio Longitudinal Study of Aging, or SALSA -- a large, population-based study of the disablement process in elderly Mexican Americans and European Americans.

The researchers examined the data to determine the relationship, if any, between diet soft drink consumption and long-term changes in waist circumference.

Measures of height, weight, waist size and diet soda intake were recorded at SALSA enrollment, and again at during three follow-up exams over the following ten years.

The researchers compared long-term changes in waist circumference for diet soda drinkers versus non-drinkers during all follow-up periods, and adjusted for age, waist size, diabetes status, physical activity level, neighborhood of residence, smoking status, gender, ethnicity and education levels.

The data revealed that, as a group, people who consumed diet soft drinks experienced 70 percent greater increases in waist circumference than those who did not drink diet sodas.

Additionally, participants who said they consumed two or more diet sodas per day experienced waist circumference increases 500 percent greater than those of non-users.

The results have potentially serious implications, since abdominal fat is a major risk factor for diabetes, cardiovascular disease, cancer and other chronic conditions, the researchers said.

"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," wrote the study's authors.

Meanwhile, a separate but related study using mice found that consumption of the artificial sweetener aspartame resulted in elevated blood sugar levels.

The University of Texas researchers studied the relationship between oral exposure to aspartame, a calorie-free sweetener used in some diet sodas, and fasting glucose and insulin levels in 40 diabetes-prone mice.   The scientists fed one group of mice food to which both aspartame and corn oil were added, while another group of mice ate food with only corn oil added.

After three months of eating this high-fat diet, the mice that consumed the aspartame showed elevated fasting glucose levels, but equal or diminished insulin levels, consistent with early declines in pancreatic beta-cell function.

Beta cells are responsible for making insulin, the hormone that lowers blood sugar after a meal.  An imbalance ultimately leads to diabetes.

"These results suggest that heavy aspartame exposure might potentially directly contribute to increased blood glucose levels, and thus contribute to the associations observed between diet soda consumption and the risk of diabetes in humans," wrote the study's senior author, Gabriel Fernandes, professor of rheumatology and clinical immunology at the University of Texas.

The latest findings will likely disappoint the millions of people who drink low calorie artificial sweetened drinks to lose weight. In the United States alone, the number of people who eat foods containing artificial sweeteners has doubled to 160 million during the past 20 years.


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