Earlier studies that I reviewed here indicated that when we take our food in liquid form rather than in a solid one, we consume more calories that day. And now a big new study shows that when we cut back on the amount of liquid calories that we consume, we do lose weight.
But, unlike the earlier studies, the new one finds only one liquid culprit: sugar-sweetened beverages. No other type of beverage is associated with a change in weight.
This is good news for people with diabetes. More than 85 percent of us are overweight or obese, according to a survey by the U.S. Centers for Disease Control and Prevention.
Six other beverages tested in the new study had little or no effect on the weight of the participants. They are diet drinks sweetened with artificial sweeteners, milk with four different amounts of fat, 100 percent fruit and vegetable juices, coffee and tea with sugar, coffee and tea without sugar, coffee and tea sweetened with artificial sweeteners, and all sorts of alcoholic beverages.
The only culprit they found was regular soft drinks, fruit drinks, fruit punch, or any other high-calorie beverage sweetened with sugar. When participants in the study cut back by 1 serving of 12 fluid ounces per day, they lost an average of 1.1 pounds after six months and 1.5 pounds after 18 months.
Researchers from the Johns Hopkins School of Medicine, the National Heart, Lung, and Blood Institute, Duke University, the Pennington Biomedical Research Center, the Kaiser Permanente Center for Health Research, the University of Alabama, and Pennsylvania State University cooperated in this 18-month randomized, controlled, behavioral intervention. They conducted a prospective study of 810 adults aged 25 to 79.
Only the abstract of the study in the April 2009 issue of the American Journal of Nutrition is online. But at my request the Johns Hopkins Bloomberg School of Public Health sent me a PDF of the full-text.
The authors of the new study found a stronger weight-loss effect from the reduction in liquid calories in sugar-sweetened beverages than from reducing a like amount of solid calories. They aren't sure why, but have three possible explanations.
First, because we don't chew liquid beverages this might result in decreased pancreatic exocrine and endocrine responses compared with eating solid foods. Second, because our stomachs empty beverages faster than solid food, this may generate weaker signals that would lead to consuming more.
But, I can't buy those explanations, because the only culprits are sugar-sweetened beverages. I do buy their third explanation, which is related to the high fructose content of sugar-sweetened beverages.
The sugar in question is, of course, sucrose. And sucrose is half fructose.
"Long-term consumption of a large amount of fructose can promote fat storage and excessive food intake through an increase in de novo lipogenesis [the new conversion of excess dietary carbohydrates into fat] and changes in postprandial hormonal patterns," the article states. Regular readers of my articles here will recognize my growing concern with fructose.
The authors of the new study also suggest a reason why drinking the other six types of beverages in the study wasn't associated with weight change. Perhaps it's because the protein, fat, or fiber slows stomach emptying.
Of course, some of the types of beverages they included in the study, including coffee or tea alone or sweetened with artificial sweeteners, don't add any calories. I will stick with these drinks as well as with copious amounts of pure water.