Consuming low-calorie drinks may increase the risk of putting on weight, according to a new study.
The new research suggests that people who choose diet drinks containing artificial sweeteners tend to overcompensate and consume more calories than those who do not.
Although the rise in obesity has corresponded with a growth in low-calorie soft drinks, designed to make keeping weight down easy by replacing sugar with saccharine or other sweeteners, scientists who conducted experiments using rats at Purdue University in Indiana, have suggested that the opposite may be happening.
They found that rats fed on yogurt sweetened with saccharine ate more calories, gained more weight and put on more body fat than rats that were given yogurt sweetened with glucose.
Susan Swithers and Terry Davidson, who conducted the experiments, have suggested that by breaking the connection between a sweet sensation and high-calorie food, the use of saccharine changes the body’s ability to regulate how many calories it consumes.
“The data clearly indicate that consuming a food sweetened with no-calorie saccharine can lead to greater body-weight gain and adiposity than would consuming the same food sweetened with a higher-calorie sugar,” they conclude in their report, which is published in the journal Behavioral Neuroscience.
They admit that their results may seem counterintuitive and might not be welcome to nutritionists and doctors who have long recommended low-calorie or no-calorie sweeteners. But they say that their findings match emerging evidence that people who drink more diet drinks are at higher risk of obesity and metabolic syndrome, a collection of medical problems such as abdominal fat, high blood pressure and insulin resistance that put people at greater risk of heart disease and diabetes.
People and animals learn that eating certain foods has consequences. Sweet tastes signal calories. If that link is broken, the researchers suggest, then the individual loses the ability to judge how many calories are being consumed. One controversial theory is that calorie consumption is signalled by a rise in body temperature after eating. The greater the rise in body temperature, the more aware the individual is that a lot of calories have been consumed.
In the experiments, the rats that were used to eating low-calorie yogurt showed a smaller rise in temperature after eating a different, calorie-loaded meal. It appeared that their ability to detect calories had been blunted, leading to overeating.
Normally, the researchers say, sweet foods provide a stimulus that strongly predicts that someone is about to take in a lot of calories and their ingestive and digestive reflexes gear up for that intake. But when false sweetness is not followed by lots of calories the system gets confused. Thus, they argue, people on low-calorie diets may eat more — or expend less energy — than they otherwise would. If their theory is correct, then artificial sweeteners such as aspartame, sucralose and acesulfame K, which taste sweet but do not provide calories, could have similar effects.