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Lab study questions sweeteners for weight control

By Stephen Daniells , 11-Feb-2008

Sweetening foods with artificial sweeteners like saccharin may lead to increased body weight and fat build-up, suggests a study with rats that goes against intuition.

Male rats fed yoghurt sweetened with glucose or saccharin, and found that animals fed the artificial sweetened food gained body weight and body fat, reports the study in the journal Behavioral Neuroscience, published by the American Psychological Association (APA). "The data clearly indicate that consuming a food sweetened with no-calorie saccharin can lead to greater body-weight gain and adiposity than would consuming the same food sweetened with a higher-calorie sugar," wrote Susan Swithers and Terry Davidson from Purdue University. The research challenges previous findings in this area, including a review published last year in the European Journal of Clinical Nutrition, which concluded that low-calorie (or no-calorie) sweeteners may be of help in resolving the obesity problem. The new study used 27 male Sprague-Dawley rats and fed them a sweet taste from glucose (caloric intake) or saccharin (no calories). The Purdue researchers report that consumption of foods containing artificial sweeteners resulted in a subsequent increase in caloric intake, as well as body weight and adiposity increases. Moreover, a blunted thermic responses to sweet-tasting diets was observed. In attempting to rationalise the findings, Swithers and Davidson suggested that sweet foods may provide a "salient orosensory stimulus", said to strongly predict when someone is about to take in a lot of calories. They said that ingestive and digestive reflexes prepare individuals for that intake, but when sweetness is not accompanied by calories, the system gets confused. "This interference could lead to reduced energy utilisation and, ultimately, to increased weight gain," they wrote. "The generality of findings obtained with rats in the laboratory to humans in their much more complex food environments can and should be questioned," wrote Swithers and Davidson. "However, it is conceivable that just as exposure to non-predictive sweet taste-calorie relationships in the laboratory appears to promote increased body weight and body adiposity in rats, the widespread use of non-caloric sweeteners in the food environment of humans may have similar effects on the predictive validity of sweet tastes and ultimately on the normal ability of humans to control their intake and body weight." The study is at odds with previous studies, particularly those in humans. The review published in the European Journal of Clinical Nutrition evaluated a variety of laboratory, clinical and epidemiological studies on low-calorie sweeteners, energy density and satiety. "Low-calorie sweeteners reduce the energy of most beverages to zero and lower the energy density of many foods," said review co-author, Adam Drewnowski, director at the Center for Public Health Nutrition at the University of Washington. "In the final analysis, all health experts agree that weight loss is best achieved by a combination of reducing caloric intake, lowering energy density of the diet, and increasing physical activity," he said. "By all accounts, low-calorie sweeteners do help. Suggesting that low-calorie sweeteners actually cause people to gain weight is an irresponsible direct application of rat models to dietary counselling and to public health," concluded Drewnowski. Commenting on the new study, Beth Hubrich from the Calorie Control Council, an association representing low- and reduced-calorie foods and beverages, said: "This study oversimplifies the causes of obesity." "The causes of obesity are multi-factorial. Although surveys have shown that there has been an increase in the use of 'sugar-free' foods over the years, portion sizes of foods have also increased, physical activity has decreased and overall calorie intake has increased," she added. Sources: Behavioral Neuroscience February 2008, Volume 122, Number 1, doi: 10.1037/0735-7044.00.0.000 "A Role for Sweet Taste: Calorie Predictive Relations in Energy Regulation by Rats" Authors: S.E. Swithers, T.L. Davidson, European Journal of Clinical Nutrition Volume 61, Pages 691-700, doi:10.1038/sj.ejcn.1602649 "Intense sweeteners, energy intake and the control of body weight" Authors: F. Bellisle and A. Drewnowski

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