It is widely believed by the public that replacing sugars with artificial sweeteners will help reduce calorie (energy) intake and aid weight loss. As a result sales of foods and drinks sweetened with artificially sweeteners are at an all time high, as are rates of overweight and obesity.

However, while appropriate use of artificial sweeteners may help control energy intake and bodyweight in the short-term, little is known about the long-term impact of artificial sweetener consumption on energy intake and body weight.

A lower intake of energy relative to energy expenditure promotes weight loss. Therefore, it would make sense that substituting foods and drinks containing artificial sweeteners for those with sugar, weight loss would follow. However, the science is not as straight forward as it may seem: the body is capable of sensing and adapting to a reduced energy intake, and as a result people may compensate for this by eating more later.

Professor David Benton, of the University of Wales, Swansea, conducted a review of the scientific evidence looking at the effect of artificial sweeteners in weight control and energy intake. Publishing his findings in Nutrition Research Reviews, Professor Benton concluded that at present the scientific evidence suggests there is a lack of convincing evidence to draw firm conclusions on the role of artificial sweeteners on long-term energy intake and bodyweight regulation. Current evidence suggests that, although artificial sweeteners may be helpful in the short-term, there is little long-term benefit of in people of normal, body weight.

Professor Benton suggests this is because “consumption of artificial sweeteners or low-energy foods tends to be followed by an increase in energy intake to make up for the lost energy in people of a normal bodyweight”. The evidence as its stands, suggests that men, rather than women, and children rather, than adults, are better at compensating. However, people who exercise dietary restraint (i.e. watch what they eat carefully)may benefit from artificial sweeteners as they tend not to compensate for energy intake.

Professor Benton suggests that following a low-fat diet is best for weight loss. “Energy-dense diets tend to be associated with obesity, and energy-dense foods tend to be high in fat and have a low water content”. High-carbohydrate diets, however, tend to be low in fat. He adds “a number of studies suggest that the use of artificial sweeteners leads to increased consumption of fat, which in theory could lead to weight gain in unrestrained eaters” as gram for gram fat provides more than twice the calories of sugar. There are a number of reasons why this may be, including that fact that carbohydrates, when consumed as solids, promote satiety (feelings of fullness) more than fat. Therefore, people who eat high fat meals may end up eating more energy than people who eat high carbohydrate meals.

It is clear that artificial sweeteners are not a magic solution to all bodyweight problems but may be helpful to some people as part of an overall diet and lifestyle conducive to slimming or weight control.

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