I would never have guessed that chewing a piece of sugar-free gum after eating could boost diet-induced thermogenesis (DIT) and fat oxidation. I’m of course talking about the 25-50% increase in DIT observed in a small group of healthy men from Hamada et al’s latest study in the journal Obesity.
These researchers recruited 12 healthy, normal-weight young men and had them complete four experimental trials in a randomized crossover design (figure 1). Each trial involved 20 minutes of baseline measurements (gas-exchange variables, splanchnic circulation, and blood samples), followed by consuming a test meal as rapidly or slowly as possible, and completed with 180 minutes of post-meal measurements. Additionally, for 15 minutes after finishing the test meal, 3 kcal of sugar-free gum was chewed or 3 kcal of sugar was consumed. Accordingly, the four trials were rapid-eating with gum (RG), rapid-eating without gum (RN), slow-eating with gum (SG), and slow-eating without gum (SN).
Gas exchange and substrate oxidation
As can be seen in figure 2 below, chewing gum significantly increased oxygen consumption (VO2) and DIT for 45-60 minutes after the meal ended in both the rapid and slow-eating conditions, despite the gum chewing only lasting for 15 minutes. Respiratory exchange ratio (RER) was largely unaffected however. *P
Another interesting observation is that eating the meal slowly resulted in greater DIT than eating the meal quickly, and both oxygen consumption and DIT remained significantly elevated above baseline values for a longer period of time.
Looking more specifically at substrate oxidation (figure 3), chewing gum after the meal significantly increased protein oxidation in the rapid-eating trials only. For whatever reason, this may relate to the number of chews or chewing duration, as eating slowly significantly increased protein oxidation for the entire 3-hour post-meal measurement period while rapid-eating did not. This in turn may have “hidden” a significant effect from the gum chewing during these trials.
Carbohydrate oxidation was significantly increased and fat oxidation significantly reduced in all four trials, which is to be expected when you eat a test meal containing spaghetti and orange juice. Nonetheless, chewing gum did appear to lessen the effect and preserve fat oxidation, especially at the 30-45 post-meal marks.
A lot of the time-course changes were not statistically significant and unimpressive. However, when the data is aggregated as the total change over the 180-minute post-meal period, another picture is painted. Chewing gum led to an overall significant increase in DIT by 48% in the rapid-eating trials and by 25% in the slow-eating trials. This difference is likely because DIT was significantly greater in the slow-eating trials vs the rapid-eating trials, so there was less room for improvement.
Accumulated protein oxidation was also significantly greater in the slow-eating trials compared with the rapid-eating trials, but accumulated carbohydrate and fat oxidation levels did not differ significantly between non-gum-chewing and gum-chewing trials for both rapid-eating and slow-eating trials.
Pretty impressive findings if I do say so myself. At least, they are on the surface. Once we consider that the absolute increase in DIT induced by chewing gum ranged from 6-8 kcal, things change. Certainly this makes up for the 3 kcal that the gum provided, but it is certainly nothing to be excited over. Although, I suppose that chewing a larger amount of gum for a longer period of time could have a more pronounced effect.
Rather than chew gum, perhaps we should eat our food slowly. After all, the slow-eating trials averaged a 2-fold increase in DIT compared to the rapid-eating trials. This still only amounted to a 15 kcal difference, however. Moreover, protein oxidation was significantly increased, although the physiological significance of this finding is unclear. Interestingly, these differences were apparent despite the meal time being 10 vs 5 minutes in the slow and rapid eating trials, respectively.
So while the authors of this study happily conclude that “these results imply that slow eating and postprandial gum chewing can help weight management,” I would argue that reality begs to differ. You would be better off eating more quickly and using that extra 5 minutes you saved going for a walk. Or chew the gum to stave-off hunger. Then it could be a dieting aid.