The role of low-calorie sweeteners in the prevention and management of overweight and obesity: evidence v. conjecture

December 13, 2017 — A recent review published in Proceedings of the Nutrition Society examined the results of intervention studies to determine if claims undermining the theory that low-calorie sweeteners affect calorie intake, and thus body weight, are substantiated scientifically. [Peter J. Rogers, University of Bristol] Rogers provides a brief review of sweet taste and three hypotheses that have resulted in claims that LCS may not be beneficial in weight gain. While preference for sweet taste is inborn, the function for human liking of sweet taste is less clear. Some hypothesize a newborn’s preference for sweet taste ensures adequate intake while it is unclear why preference for nutrients with higher caloric density is not primary. Efforts to better understand sweet taste have used various sweet compounds while other studies have explored the relationship between sweet taste and food intake based on these three hypotheses:

  • LCS disrupt the learned control of energy intake (sweet taste confusion hypothesis);
  • Exposure to sweetness increases desire for sweetness (sweet tooth hypothesis);
  • Consumers might consciously overcompensate for ‘calories saved’ when they know they are consuming LCS (conscious overcompensation hypothesis)

Rogers reviews evidence from human, animal, and meta-analysis studies and states “Recent meta-analyses of acute and longer-term randomized controlled studies in human participants found clear evidence that consumption of LCS compared with sugar does indeed reduce energy intake and body weight.” Laboratory studies have shown that adults and children do consume more calories in a test-meal after having LCS than when they have a sugar preload. However, the total intake of the pre-load and meal is less when people consume LCS than sugar. Because laboratory studies may not have similar results as “real-life” scenarios, long-term studies have also been conducted and have shown effect sizes of LCS v. sugar to be −1·41 (95% CI −2·62, −0·20) kg for adults and −1·02 (95% CI −1·52, −0·52) kg for children. Prospective studies also show no overall association between LCS consumption and body weight though it should be noted that reverse causality may be evident in some studies with an effect. Lastly, rodent studies have shown LCS reduced weight or had no effect in mice and rats.

In reviewing animal studies that were conducted to test whether low-calorie sweeteners disrupt the learned control of energy intake, Rogers notes that findings from initial studies have not been replicated and that results contradict the flavor-confusion hypothesis. Furthermore, he notes a problem with the reasoning that sweetness could be a useful guide for the control of energy intake because level of sweetness does not reliably predict the energy content of different foods and beverages in the human diet.

Lastly Rogers evaluated the evidence that individuals may overcompensate and consume more calories than those “saved” by consuming a product with LCS compared with a sugar-sweetened product. He notes that short-term laboratory studies were conducted to reduce the risk that individuals knew the difference between LCS- and sugar- sweetened products. This differs from real world scenarios in which consumers will likely be aware of consuming a relatively low-energy product. The author states “In summary, there is little evidence for conscious compensation for LCS consumption. Studies however have not modelled all everyday life uses of LCS. For example, while there might be little or no conscious compensation when LCS are substituted for sugar as part of ‘calorie counted’ weight loss diet, full or even overcompensation may occur when the choice of LCS is used as an excuse for indulgence. Finally, conscious compensation can be ruled out as influencing overall energy intake if consumers are unaware they are consuming LCS.

Rogers reached the following conclusions regarding each of the claims considered:

  • LCS and energy intake: “sweetness is not a reliable predictor of energy density”, therefore absolving LCS from the charge that they disrupt the control of energy intake.
  • LCS and desire for sweetness: studies indicate that consumption of LCS beverages does not increase energy intake compared with water, and may have the advantage to some extent of satisfying desire for sweetness when consumed shortly before or with a meal.
  • LCS and overcompensation: “There is little evidence for conscious compensation for LCS consumption.” When using preload test-meals, there is partial compensation in energy intake for the difference in energy content of LCS versus sugar.

The overall conclusion is that the current body of evidence suggests LCS can be expected to reduce sugar and overall caloric intake and at a minimum, any counterproductive effects of LCS are outweighed by incomplete compensation for the reduced energy content of LCS foods and beverages.

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