The average American has been increasing in weight at least since the 1950s. The reason for this increase in BMI has been debated for decades, but still there is no consensus as to what is causing it. There is no debate today that most Americans are overweight or obese. For many years it was argued the major cause was reduced activity. That may have been a contributing factor years ago, but there has been little change in the average activity of Americans since about 1980 and yet the average American keeps getting fatter. So while activity may play a role, it is unlikely to be the major driving force expanding the waistline of most Americans today. One increasingly likely culprit promoting increased adiposity is the gradual increase in beverage calories, particularly in sugar sweetened beverages, over the past several decades. Indeed, the percentage of total calories coming from beverages has increased dramatically for many years. Back in the 1950s and 1960s perhaps 10-12% of the average American’s total calorie intake came from drinks. Today the percentage of beverage calories has more than doubled for the average American. This marked increase in beverage calories and particularly sugar-sweetened drinks has been driven in part by larger average portion sizes and in part by an increased variety of beverages, particularly those rich in sugar. Back in the 1950s, most sugar-containing beverages were sodas and fruit juices. A standard bottle of Coke back in the 1950s had but 6 ounces. Today the “small” soda serving size is at least 2 to 3 times greater. In addition, there are now far more fruit drinks, “energy” drinks, “sports” drinks, and a growing variety of sugar-sweetened teas and coffees that were either not available or rarely consumed back in the 1950s and 1960s, when most American maintained a BMI of less than 25.
Sugar-Rich Drinks Promote Weight Gain
A study comparing the impact of consuming sugar as either soda or jelly beans over several weeks found that subjects compensated for the extra calories coming from the jelly beans and spontaneously reduced their intake of other sources of energy. However, this compensatory reduction in other sources of calories failed when the same amount of sugar was added to the diet as a soda drink. Not surprisingly, after 4 weeks weight was stable in those consuming the extra sugar as jelly beans whereas average weight increased significantly when the same amount of sugar was consumed as a soda drink. [DiMeglio DP, Mates RD. Liquid versus solid carbohydrate: effects on food intake and body weight. Int J Obesity 2000;24:795-800]. A meta-analysis of 88 studies looking at the association between soft drink consumption and BMI “..found a clear association of soft drink intake with increased calorie intake and body weight.” [Vartanian LR, et al. Effects of soft drink consumption on nutrition and health: a systematic review and met-analysis. Am J Pub Health. 2007;97:1-10]. A more recent analysis of data from three different prospective studies with over thirty thousand subjects followed concluded: “The genetic association with adiposity appeared to be more pronounced with greater intake of sugar sweetened beverages.” [Qi Q, et al. Sugar-sweetened beverages and genetic risk of obesity. N Engl J Med. 2012. DOI:10.1056/ NEJMoa1203039]. Simply put, those who appear to be more genetically prone to gain weight appeared to be the ones most likely to put on those extra pounds in response to consuming more sugar-sweetened drinks.
Another study in the same September 21, 2012 issue of the New England Journal of Medicine by researchers affiliated with Harvard University randomly assigned 224 overweight or obese adolescents to either an experimental or control group. Reported consumption of sugar-sweetened drinks in the two groups at baseline were the same on average. The experimental group intervention consisted largely of the researchers delivering sugar-free beverages to the homes of the experimental group of teenagers for one year. The parents of the experimental group were encouraged to stop buying sugar-sweetened beverages (including fruit juices) but there was no discussion about reducing calorie intake or increasing activity. By contrast, the parents of the control group were simply mailed $50 gift cards to a local supermarket twice during the year with no instructions on how the money should be spent. During the first year of the study, the control group gained an average of a bit more than 4 pounds more than the experimental group. Both groups were followed a second year without any intervention, and after the second year, the percent body fat in the two groups was not significantly reduced.
Bottom Line: The evidence continues to mount that calories from sugar-sweetened drinks provide little satiety and so promote weight gain, particularly in those genetically prone to put on excess body fat.
By James J. Kenney, PhD, RD, FACN
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.