There is little evidence for altered sweet taste in obesity. However, overweight and obese subjects generally prefer high fat, sweet stimuli. Here we examined brain responses to sweet tastes.
Eleven normal weight (BMI 22.5±2.2 kg/m2, age 48±12 y) and 11 women with obesity (BMI 50.2±9.2 kg/m2, age 43±9 y) rated the intensity and their liking of sucrose solutions (0, 0.1, 0.4, 0.86 & 1.05 M) presented in a three-block randomized design and underwent functional magnetic resonance imaging (fMRI) to assess brain responses to 0.40M and 0.10M sucrose sprayed onto the tongue as compared to water (7 sucrose and 17 water trials in each 5:52 min long scan). The 0.40M and 0.10M responses were acquired in separate alternating scans, counterbalanced across subjects.
There was no difference in rated sucrose intensity or preferred concentration between normal weight and obese subjects. Across the whole sample, BOLD activation from [Sucrose (0.40M) > water] occurred in bilateral gustatory insula, left sensorimotor cortex/rolandic operculum, pre-SMA, left middle frontal gyrus, left posterior lateral orbitofrontal cortex and bilateral ventral striatum (peak voxel significance p<0.005, k>20). A positive association between BMI and the [Sucrose (0.40M) > water] contrast appeared in the left and right gustatory insula, and left rolandic operculum, which remained after adding the covariate of sucrose solution liking. The [Sucrose (0.40M) > water] contrast associated positively with liking in the left ventral postcentral gyrus. There were no negative correlations between BMI and the [Sucrose (0.40M) > water] contrast and no correlations with the [Sucrose (0.10M) > water] contrast.
These preliminary findings suggest that women with obesity have greater sweet taste-induced responses in gustatory cortex, consistent with reported sweet food preferences in obesity. These data might also suggest that gustatory cortex reactivity is altered by adiposity, possibly complicating diet compliance.