This is the first study to directly test the effects of the natural sweetener, stevia, on food intake, satiety, and postprandial glucose and insulin levels in humans. The key finding was that participants did not compensate by eating more at either their lunch or dinner meal when they consumed lower calorie preloads containing stevia or aspartame compared to when they consumed higher calorie preloads containing sucrose. In other words, even after a lower calorie preload, food intake at subsequent lunch and dinner meals was not increased and discretionary food intake did not differ between the conditions. Thus, participants’ total caloric intake was lower in the stevia and aspartame conditions, compared to the sucrose condition, solely due to the difference in caloric amounts of the preloads used in this study. Our findings are consistent with previous studies, which have found that changing the energy density of a food does not result in an accurate compensation in energy intake at subsequent meals (Levitsy, 2001
; Rolls, Hetherington, & Laster, 1988
; Rolls, Laster, & Summerfelt, 1989
). Other studies have also found that consumption of preloads an hour and a half before testing did not influence the amount consumed in the following meal (Rolls et al., 1991
). Findings such as these suggest that the eating behavior of humans may not be strongly related to previous caloric intake, at least in the short-term. Other studies suggest that compensation may not occur even over relatively long time periods. For example, sucrose-sweetened food and beverages resulted in a 1.6 kg weight gain in overweight individuals whereas artificially sweetened foods and beverages resulted in a 1.0 kg weight loss over a 10 week period (Raben, Vasilaras, Moller, & Astrup, 2002
Consumption of stevia in preloads significantly lowered postprandial insulin levels compared to both aspartame and sucrose, as well as postprandial glucose levels compared to sucrose. Consumption of aspartame in preloads also reduced postprandial glucose compared to sucrose at twenty minutes following consumption of the preload. These effects on postprandial glucose levels are likely due in large part to the lower caloric and carbohydrate intake in the aspartame and stevia preloads compared to the sucrose preloads. However, these effects do not appear to be solely due to the lower calorie preloads in the stevia condition, as participants consumed identical calorie amounts in the preloads used in both the stevia and aspartame conditions. If future studies confirm these findings, then stevia may be helpful in managing postprandial hyperglycemia, which recent studies indicate is an important contributor to the development of insulin resistance and Type 2 diabetes (Viswanathan, Clementina, Nair, & Satyavani, 2007
Despite consuming significantly fewer calories when provided preloads sweetened with stevia or aspartame (as compared to sucrose) in a blinded condition, participants reported similar levels of satiety in all three conditions. Since each of the preloads sweetened with sucrose contained 203 more kcal than the preloads sweetened with stevia or aspartame, this finding suggests that the additional calories provided from sucrose did not increase satiety levels, at least in the short-term. However, future studies are needed to examine this hypothesis since the caloric content of the preloads in this study was not equivalent in all three conditions.
In either case, our findings suggest that using stevia or aspartame in place of sucrose (i.e., sugar) in the diet may be an effective strategy to manage food intake since hunger and satiety levels were similar in all three conditions. In terms of hedonic ratings, participants rated the preloads containing aspartame as having a more pleasant taste than the preloads containing stevia or sucrose. There were no differences, however, in the hedonic ratings of the stevia and sucrose preloads in terms of appearance, aroma, sweetness, or texture. This suggests the observed difference in food intake were not related to the hedonic value of the three different preloads.
One limitation of the present study is that eating behavior was measured in a laboratory setting rather than the participant’s natural environment. Similarly, the design of the present study was not in line with typical eating patterns, which may limit the generalizabilty of our findings. Although some studies suggest that participants may increase their food intake in laboratory settings due to the availability of free food (Gosnell, 2001
), other studies have found eating behavior in the laboratory to be consistent with eating behavior in the natural environment (Kissileff, Thornton, & Becker, 1982
) and to be stable over time (Martin et al., 2005
). Another potential limitation of the present study is that food intake was only measured over the course of a single day; thus, we were unable to evaluate whether compensation in food intake occurs over the long-term. We also did not collect information about the participant’s dinner the night before coming to the laboratory, which has been shown to influence the glycemic response the next day (Wolever, Jenkins, Ocana, Rao, & Collier, 1988
). Finally, a control condition without a sweetener was not included in this study. Although this condition would allow for further testing of the effects of sweetness on food intake, this was not the primary purpose of the present study. Rather, the present study was designed to test the effects of the natural sweetener, stevia on food intake, satiety, and postprandial glucose and insulin levels in humans as compared to both asparatame (positive caloric control) and sucrose .
This study also had a number of strengths. First, both lean and obese individuals were included, increasing the generalizability of these findings. Second, food intake was directly measured, and satiety measurements were taken at identical time intervals as blood glucose and insulin levels. Third, a pilot study was initially conducted to determine the appropriate gram and calorie amounts to provide in the preloads. Moreover, all preloads were matched for gram weight, and the aspartame and stevia preloads were matched for caloric content.
In conclusion, participants did not compensate by eating more at either their lunch or dinner meal and reported similar levels of satiety when they consumed lower calorie preloads containing stevia or aspartame than when they consumed higher calorie preloads containing sucrose. Additionally, stevia preloads reduced postprandial blood glucose and insulin levels, suggesting stevia may assist with glucose regulation. These effects appear to be independent of reductions in caloric intake, as participants consumed similar calorie amounts in both the stevia and aspartame conditions.