09/02/2011 08:12 am ET Updated Nov 02, 2011

Soda: Does It Fizzle Your Health?

Despite fewer super-sized meals, American's waistlines continue to expand, according to a recent study funded by the National Institutes of Health. According to University of North Carolina at Chapel Hill researchers who conducted the study and examined surveys of daily eating habits over a 30-year period, the number of daily meals and snacks consumed by U.S. adults rose to 4.8 in 2006 from 3.8 in 1977.

Many health professionals say that frequent eating in small doses revs up the metabolism and controls hunger, and is a healthier way of eating than three big meals. However, much consideration must also be given to what and how much you eat over the course of the day -- not just how often you eat.

Case in point: The analysis also found that although the size of meal portions has stabilized in recent years, the number of total calories consumed is rising. By 2006, the end of the period studied, Americans were consuming 570 more calories per day than they did in the late 1970s. A chief culprit behind the calorie gain: Americans now consume 220 more calories daily from sugar-sweetened soft drinks than they did in the 1960s, the study found.

So it's okay to switch to diet soda, right? Not so fast. Two new studies presented recently at the American Diabetes Association's (ADA) Scientific Sessions have linked drinking diet soda to weight gain and that the artificial sweeteners in them could potentially contribute Type 2 diabetes.

In one study, researchers from the School of Medicine at The University of Texas Health Science Center San Antonio, looked at aggregate data from 474 older adults in the San Antonio Longitudinal Study of Aging, or SALSA. At the time of enrollment and at three follow-up exams thereafter, all participants reported their diet soda intake and were measured for height, weight and waist circumference. The researchers wanted to track any association between diet soda drinking and body fat over time.

People who said they drank two or more diet sodas a day experienced waist size increases that were six times greater than those of people who didn't drink diet soda, according to researchers from the University of Texas Health Science Center at San Antonio. Researchers said their results were adjusted for other contributing factors like diabetes status, leisure-time, physical activity and age.

The data didn't say why diet sodas might play a role in weight gain, but previous research suggests it has to do with the idea that the brain is wired to expect a big load of calories when foods taste sweet or fatty, but because diet foods fail to deliver, it throws the brain out of whack. Studies in animals suggest that artificial sweetener consumption may lead to even more eating and weight gain -- perhaps in part because it triggers the body to start storing more calories as fat.

A second study that found the sweetener aspartame raised blood sugar levels in diabetes-prone mice. The researchers, also from the School of Medicine at The University of Texas Health Science Center San Antonio, fed aspartame -- a calorie-free sweetener used in some diet sodas -- to diabetes-prone mice. One group of mice ate chow to which both aspartame and corn oil were added; another other group ate chow with only corn oil added. After three months, the mice that ate aspartame showed elevated blood sugar levels. The findings aren't directly translatable to humans, but may still be meaningful. So ... maybe it's time to switch to carbonated water?