Diet Soda and Belly Fat: A Growing Concern

A growing body of evidence is showing that it might not just be added sugar, but also artificial sweeteners, that are contributing to the rapidly rising rates of obesity and diabetes in America.

An important new long-term analysis1 of 375 seniors in Texas has shown a clear relationship between the number of diet sodas consumed on a daily basis and abdominal obesity – the belly fat that serves as the most obvious indicator of underlying metabolic syndrome and, with it, increased risk of diabetes and cardiovascular disease.

The study, which was conducted by researchers in the University of Texas Health Science Center in San Antonio, followed a group of Mexican-American and European-American seniors for an average of 9.4 years, with three follow-up visits during that time.

The study found that the increase in waist circumference (3.16 inches over 9 years) for participants who drank one or more diet sodas per day was nearly four times the increase that non-soda drinkers experienced (0.8 inches). Occasional diet soda consumers (0-1 sodas per day) fell about mid-way between those, with an average waist increase of 1.83 inches over the course of the study.

Interestingly, the authors found that diet soda drinkers were similar to those who don’t consume diet drinks with respect to age and sex, but had higher education levels and were more likely to live in the suburbs and to be of European descent, less likely to smoke and more likely to expend more energy during leisure times – all elements we would normally associate with greater health-promotion behavior.  Even so, diet soda drinkers had higher rates of obesity from the start of the study (45% obese) than non-drinkers (27.8%). The researchers adjusted for these differences in the study, but noted that these are precisely the people who are most likely to replace sugar-sweetened soda with diet drinks in an effort to lose weight.

These results are consistent with a growing body of research in both humans and animals, showing that frequent consumption of diet soda or artificial sweeteners is associated with greater body mass index (BMI), obesity and metabolic syndrome.

Why, precisely, that is happening is still unclear. Previous research2 had indicated that artificial sweeteners could be a major cause of both obesity and diabetes by changing the balance of bacteria in our guts, favoring the microbes that induce glucose intolerance (see previous SugarScience Alert). 

Regardless of the biological causes, this study raises concerns about the safety of drinking not just sugar-sweetened sodas, but also substituting diet sodas, especially for people already at risk for obesity, heart disease and diabetes.

  • [1]Fowler, S.P., Williams, K., & Hazuda, H.P. (2015, March 17). Diet Soda Intake Is Associated with Long-Term Increases in Waist Circumference in a Biethnic Cohort of Older Adults: The San Antonio Longitudinal Study of Aging . J Am Geriatr Soc . doi:10.1111/jgs.13376. Retrieved from
  • [2]Suez, J., Korem, T., Zeevi, D., Zilberman-Schapira , G., Thaiss , C.A.., Maza , O., Israeli, D., Zmora, N., Gilad, S., Weinberger, A., Kuperman, Y., Harmelin, A., Kolodkin-Gal, I., Shapiro, H., Halpern, Z., Segal, E., & Elinav, E. (2014, October 9). Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature (514), 181–186. doi:10.1038/nature13793. Retrieved from

Heart disease

A broad term for a group of chronic diseases of the heart, these diseases include problems with blood supply to heart muscle, problems with heart valves and the electrical system of the heart. Another term you will see used to mean the same thing is cardiovascular disease.

SugarScience Glossary

Metabolic syndrome

Also called Syndrome X is a group of body abnormalities that go along with increased risk of cardiovascular disease, type 2 diabetes and stroke. The definition of this syndrome varies a little worldwide.

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Added sugar

Any sugar added in preparation of foods, either at the table, in the kitchen or in the processing plant. This may include sucrose, high fructose corn syrup and others.

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Diabetes mellitus

Usually shortened to just diabetes. Sometimes called sugar diabetes. Look at Type 1 Diabetes and Type 2 Diabetes for more information

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Glucose is a sugar we eat. It is found in starch. It is the main fuel for our bodies. It is the sugar measured when we have a blood test to measure the blood sugar.

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One of the three major groups of nutrients we eat. Much of this website is related to problems associated with too much fat storage in the body. Each gram of fat produces 9 calories of energy if burned by the body as fuel. Fat can be stored in many places in the body. We generally think of fat as under the skin (subcutaneous), but the fat that may be most damaging to us is the fat stored in the liver and around the organs of the abdomen (intrahepatic and visceral or abdominal or intra-abdominal)

SugarScience Glossary

SugarScience is the authoritative source for evidence-based, scientific information about sugar and its impact on health.

Laura A. Schmidt, PhD, MSW, MPH

Laura A. Schmidt, PhD, MSW, MPH, is a professor in the UCSF School of Medicine. She has dedicated her career to intervening on the social determinants of health and to understanding how lifestyle risk factors, such as alcohol and poor diet, influence chronic disease and health inequality.

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