Researchers from Purdue University have laboratory evidence that the widespread use of no-calorie sweeteners may actually make it harder for people to control their intake and body weight.
In one experiment using rats, the researchers compared the consumption of yogurt sweetened with glucose (sugar) and yogurt sweetened with zero-calorie saccharin. They found that the rats eating the artificial sweetener consumed more calories, gained more weight, put on more body fat, and didn't make up for it by cutting back later.
Researchers Susan Swithers and Terry Davidson surmised that by breaking the connection between a sweet sensation and high-calorie food, the use of saccharin changes the body's ability to regulate intake. That change depends on experience. Problems with self-regulation might explain in part why obesity has risen in parallel with the use of artificial sweeteners. It also might explain why, says Swithers, scientific consensus on human use of artificial sweeteners is inconclusive, with various studies finding evidence of weight loss, weight gain or little effect. Because people may have different experiences with artificial and natural sweeteners, human studies that don't take into account prior consumption may produce a variety of outcomes.
The study also measured changes in core body temperature. Normally, when we prepare to eat, the metabolic engine revs up. However, rats that had been trained to respond using saccharin (which broke the link between sweetness and calories), relative to rats trained on glucose, showed a smaller rise in core body temperate after eating a novel, sweet-tasting, high-calorie meal. The authors think this blunted response both led to overeating and made it harder to burn off sweet-tasting calories.
"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," the study, published in Behavioral Neuroscience, noted.
The authors acknowledge that this outcome may not come as welcome news to health-care practitioners, who have long recommended low- or no-calorie sweeteners. But they note that their findings match emerging evidence that people who drink more diet drinks are at higher risk for obesity and metabolic syndrome.
Other artificial sweeteners - such as aspartame, sucralose and acesulfame K - which also taste sweet but do not predict the delivery of calories, could have similar effects, say the researchers.
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Source: American Psychological Association