Artificial sweeteners in diet drinks and colas aren’t inert. Despite having no or low calories, they change the way the body processes sugar, and they contribute to diabetes and weight gain. In one study of 474 older adults, all participants saw their waistlines expand, yet those who reported drinking diet drinks had 70% greater increases in waistline growth than non-diet-soda-drinkers 9.5 years later. For those who consumed two or more diet drinks a day, waistline increase was 500% greater than among non-diet-soda-drinkers. Another study reported a striking dose-response relationship: increasing diet drinks was associated with escalating abdominal obesity. The more the participants consumed, the more obesity they experienced. In a study of 17 obese people, those who drank water sweetened with sucralose (Splenda®, an artificial sweetener) saw their insulin levels rise by 20%. In support of this, a recent study found consumption of artificial sweeteners drives the development of glucose intolerance through upsetting the gut microflora. These sweetener-altered microbial metabolic pathways are linked to host susceptibility to metabolic disease and obesity.
Similarly, 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. Rats fed artificial sweeteners in conjunction with their normal diet consumed more calories and got fatter. In another study, rats eating artificially sweetened yoghurt ate more chow than those eating sugar-sweetened yoghurt, so overall calorie intakes were the same. However, the rats consuming artificial sweetener gained weight at a rate faster than those eating sugar.