The claim that non-nutritive sweeteners accelerate body weight gain by disrupting sweet-calorie associations was tested in two experiments using rats. The experiments were modelled on a key study from a series of experiments reporting greater body weight gain in rats fed yoghurt sweetened with saccharin than with glucose (Swithers & Davidson, 2008). Both of the current experiments likewise compared groups fed saccharin- or glucose-sweetened yoghurt in addition to chow and water, while Experiment 1 included a third group (Control) given unsweetened yoghurt. In Experiment 1, but not in Experiment 2, rats were initially exposed to both saccharin- and glucose-sweetened yoghurts to assess their relative palatability. We also tested whether the provision of an energy-dense sweet biscuit would augment any effects of saccharin on food intake and weight gain, as seemingly predicted by Swithers and Davidson (2008). In Experiment 1 there were no differences in body weight gain or fat pad mass between the Saccharin and Control group, whereas the Glucose group was the heaviest by the final 5 weeks and at cull had the largest fat pads. Greater acceptance of saccharin predicted more weight gain over the whole experiment. Consistent with past reports, fasting blood glucose and insulin measures did not differ between the Saccharin and Control groups, but suggested some impairment of insulin sensitivity in the Glucose group. Experiment 2 found similar effects of glucose on fat mass, but not on body weight gain. In summary, adding saccharin had no detectable effects on body-weight regulation, whereas the effects of glucose on fat pad mass were consistent with previous studies reporting more harmful effects of sugars compared to non-nutritive sweeteners.
This study by Boakes et al did not confirm the theory of Swithers & Davidson (2008), claiming that low calorie sweeteners cause weight gain and actually found that saccharin did not cause higher weight gain compared to glucose, while, on the contrary, significant differences in fat pad mass were observed between the two groups, with higher g/kg fat in glucose-fed animals. The researchers from the University of Sydney, Australia, replicated the experiments by Swithers & Davidson (2008) in order to test the theory that low calorie sweeteners accelerate body weight gain by disrupting sweetness-energy associations, but their findings refute the hypothesis of the Swithers’ group.
In this study by Boakes et al, the researchers explored also the hypothesis whether prior exposure to saccharin would produce poorer energy compensation and, over time, increase energy intake and/or weight gain. In both experiments they conducted, they found that saccharin did not lead to higher energy consumption and greater weight gain compared to glucose. The authors conclude in their publication that “Our results indicate that the effects of glucose were more harmful than saccharin in terms of body weight gain and fat mass. This result is in opposition to the findings of the Swithers group and others, but is consistent with the majority of animal and human research suggesting the effects of non-nutritive sweeteners are not more harmful than those of caloric sweeteners”.