Doubt cast on role of diet drinks in weight loss

London - Do diet drinks make a useful contribution to weight loss? Not according to new research from Imperial College London where the drinks do not lead to behavioral changes that reduce overall calorie intake.

On one hand it may seem obvious that diet drinks contribute to weight loss. Take coca cola, the sugar version, for a standard measure (500mL), contains around 200 calories whereas the diet equivalents (Diet Coke or Coke Zero) contain around one calorie. Simply switching drinks and keeping all other factors equal should lead to an overall calorie reduction (depending upon how many such drinks a person consumes each day).

However, human behavior is more complex. By switching to diet drinks many people feel, according to the new research, that this 'virtuous act' allows them to reduce the amount of exercise they take or to eat greater quantities of food that is higher in fats or sugars. This may not be a totally conscious behavior either. Because diet drinks are sweet, the body may expect a calorie intake that does not occur, leading to an urge to find calories elsewhere (this stemmed from an earlier study headed "Intake of high-intensity sweeteners alters the ability of sweet taste to signal caloric consequences: implications for the learned control of energy and body weight regulation".) Thus the diet drink switch can, in some case, lead to a physiological and psychological change.

The review from Imperial College London also argues there is "no solid evidence" that low-calorie sweeteners are any better for weight-loss than full-sugar drinks. Moreover, they challenge the idea that such drinks are automatically healthier. Instead the researchers state there is no evidence that diet drinks, for example, have no affect on type 2 diabetes.

in related sugar news, Public Health England (via the BBC) has issued a warning that children are packing in so much sugar at breakfast, from breakfast cereals, that half their daily allowance has already been eaten before they arrive at school. In addition, the U.K. National Diet and Nutrition Survey shows that four- to 10-year-oldsare consuming twice as much sugar as they should be.