In this article we look at whether non-caloric beverages can help with weight loss and weight management.

There are questions about the effectiveness of the use of soft drinks with non-nutritive sweeteners in terms of weight management. These have been raised as there are various hypotheses supporting that exposure to sweetness encourages the desire for increased intake of sweet, energy-dense foods and drinks, while other theories predict that a potential reduction in energy intake may be compensated for, consciously and/or unconsciously.

Recently, the results of the SWITCH study, a 52-week randomised controlled trial, were published, that compared the consumption of non-nutritive sweeteners versus water.

The trial involved women and men with overweight or obesity who were enrolled in a weight management programme. Participants experienced a weight loss of 6.3% at 12 weeks, which was maintained at 52 weeks (7.5%).

The study found that weight loss was greater for participants who consumed sugar-free beverages compared to those who consumed water (7.5 kg versus 6.1 kg).

Another feature of the study was that a quarter of the participants were "naïve" to sugar-free soft drinks, meaning that in the 5 years before the trial, they had very rarely consumed soft drinks without sugar.

The analyses even showed that the weight loss of participants who were given soft drinks with non-nutritive sweeteners in the trial did not differ in relation to their "naivety" to them.

This contradicts the sweet taste confusion hypothesis, since it predicts that increased exposure to sweetness that would not match energy intake should undermine appetite control in this group (i.e., place an additional burden on them), compared to participants who were not "naïve" to sugar-free soft drinks since they had prior experience of this potential disadvantage.

Also, although the "sweet tooth hypothesis" and the "sweet taste confusion hypothesis" are difficult to test experimentally, the evidence against them are and growing.

The results of SWITCH are comparable to those identified in meta-analyses of previous trials that performed this comparison, which overall do not indicate differences for body weight between soft drinks using non-nutritive sweeteners and water.

The totality of the evidence, of course, is not homogeneous. For example, a previous randomised controlled trial, on which SWITCH was largely based, found a larger effect in favour of unsweetened soft drinks. In contrast, another long-term randomized controlled trial, also as part of a weight management program, found a significant effect in favor of water.

It is also worth noting that it is unlikely that the physiological effects of soft drinks with non-nutritive sweeteners on appetite and/or metabolism can explain the effects of their consumption on body weight, as meta-analyses do not indicate an effect on body weight of non-nutritive sweeteners consumed in capsules compared to placebo capsules.

On the other hand, replacing sugars with unsweetened soft drinks is not neutral with respect to individual differences in physiological and/or psychological characteristics.

For example, a large randomized controlled trial found evidence that children with a higher initial BMI compensated less for a covert reduction in energy intake achieved by replacing sugars using sugar-free soft drinks than children with a lower initial BMI.

It therefore appears that the hypotheses that state that the potential reduction in energy intake can be compensated for, consciously and/or unconsciously as well as that sweetness can increase appetite are wrong.

We can therefore say with certainty that these assumptions have been disproven and it is now clear that the data overall, including findings from properly analysed prospective cohort studies, support the use of soft drinks with non-nutritive sweeteners in weight management.

These results therefore suggest that the consumption of sugar-free soft drinks may provide a benefit, albeit rather small, in terms of weight management.

-Suprastratum: The authority on health, fitness and nutrition

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