Obesity.

In 1992 Pieramico et al. (40) reported that obese patients had significantly fewer phase III contractions that started in the stomach compared with healthy controls. This change in origin was associated with significantly lower motilin plasma levels in the obese patients compared with the lean controls. Unfortunately, hunger was not scored during the measurement.

We recently studied the association between gastric motility, motilin plasma levels, and hunger ratings in obese subjects and also found a shift in the origin of phase III contractions from stomach to duodenum in morbidly obese patients (19). Unlike the findings by Pieramico et al. (40), we found significantly elevated motilin plasma levels during all phases of the MMC and irrespective of the origin of phase III in obese patients compared with healthy controls. Although plasma levels were overall higher in the obese patients the fluctuation of motilin plasma levels was diminished (19). Our findings of elevated motilin levels are in agreement with two other studies reporting significantly higher motilin plasma levels in obesity (15, 40, 59). Hunger measurements showed lower hunger scores during phase III in the obese compared with the healthy controls, which is probably due to the shift in origin from gastric to duodenal, despite the higher motilin plasma levels (19). This shift in origin of phase III could be due to 1) a lack of motilin fluctuation or 2) a desensitization of the motilin receptor (8). Similarly, a shift toward more small intestinal phase III contractions has already been reported for elderly individuals, although their motilin plasma levels during all phases of the MMC were increased (4, 23). Differences in body mass index were, however, not evaluated between the controls and elderly, nor were their hunger scores measured and compared. In agreement with a changed MMC pattern, it has been reported that both obese and elderly subjects have a higher prevalence of SIBO (24, 35, 37, 42, 44).

After Roux-en-Y gastric bypass surgery we found that the pattern of the MMC is still present in the constructed Roux limb both 6 mo and 1 yr after surgery (19). Absence of this activity in the Roux limb can contribute to Roux-en-Y syndrome (56). Whether the stomach and bypassed duodenum still contribute to this bypassed MMC is unknown and difficult to measure manometrically. More interestingly, the motilin plasma levels both 6 mo and 1 yr after Roux-en-Y gastric bypass decreased significantly compared with the values preoperatively (19). Further research in both obese and elderly patients should be performed to clarify the clinical significance of the shift in the origin of phase III and the increased motilin plasma levels. Administration of the motilin receptor agonist, erythromycin still induced gastric phase III and increased hunger ratings in obese patients prior to bariatric surgery (19). Furthermore, our study suggests that “hedonic” rather than “physical” hunger drives food intake in obese patients. Hedonic hunger is defined as the drive to eat palatable food for pleasure in the absence of energy deficit and has been reported to be increased in obese individuals but decreases after Roux-en-Y gastric bypass surgery (46, 55). We have reported as well that hedonic hunger is decreased after Roux-en-Y gastric bypass surgery, together with a decrease in motilin plasma levels (19). The role of motilin in hedonic hunger sensations requires further attention.