Obese individuals have an increased preference for high caloric foods, such as sweets and fats. However, following gastric bypass (GBP) surgery, morbidly obese patients tend to avoid these foods. We hypothesize that this aversion may occur, in part, from permutations in taste acuity. To test this hypothesis, taste detection and recognition thresholds for the four basic tastes (salt, sweet, sour, and bitter) were assessed using a modification of the Henkin forced choice three stimulus technique. Taste acuity measurements were obtained at baseline and at 30, 60, and 90 days post-operative for six morbidly obese GBP women and ten non-surgical, lean female controls. We found nonsignificant differences in taste detection and recognition thresholds between morbidly obese and lean control study subjects at baseline, and no significant correlation between taste acuity and body size. Furthermore, in our study population of lean and obese women, ages 26 to 52, there were no significant interrelationships between baseline taste thresholds and known effectors of taste acuity, i.e., zinc levels, glycemic status, liver and kidney function, or age. Following GBP surgery, a significant up-regulation in taste acuity for bitter and sour was observed along with a trend toward a reduction in salt and sweet detection and recognition thresholds. These findings would suggest the following: (1) taste acuity does not influence taste preferences of the obese individual who has not had bariatric surgery; (2) taste effectors such as zinc, when within the range of normal values, do not alter thresholds of the 4 basic tastes; and (3) weight loss following gastric bypass surgery is associated with an up-regulation in taste acuity in the morbidly obese. Studies are currently under investigation at our center to identify the specific etiology of taste acuity upregulation in the morbidly obese following GBP surgery.

Although vitamin D deficiency has been well-documented following gastric bypass surgery, there are few studies of vitamin D status in the non-operative morbidly obese patient. We examined 25-hydroxyvitamin D (25-OHD) levels in 60 morbidly obese pre-operative females; 62% of them had 25-OHD levels below normal range (16-74 ng/ml) which were not associated with reductions in serum calcium or phosphorus, liver or kidney dysfunction, and were not significantly correlated to patients' age. However, 25-OHD levels were significantly (p < 0.0001) and negatively correlated to body mass (r = -0.49). These data suggest that low vitamin D may be associated with obesity per se. Hypovitaminosis D, when it is found in post-bariatric surgery patients, may not be caused by the surgery since it may have been present to some degree pre-operatively.

The morbidly obese and especially the super-morbidly obese (> 225% ideal body weight) often require gastric bypass surgery as treatment for long-term remission of their obesity. The extended gastric bypass Roux-en-Y (X-GBP) procedure evolved as a result of a perceived need to increase weight loss in morbidly obese subjects beyond the limitations of the regular gastric bypass Roux-en-Y (R-GBP). We compared weight loss, caloric intake, and percentage of total caloric intake from carbohydrate, protein, and fat in eight R-GBP and eight X-GBP patients at 3, 6, 9, and 12 months following surgery. We found that R-GBP and X-GBP groups were similar in age and height, adjusting for baseline weight differences (p = 0.122). Both groups demonstrated significant weight loss overtime (p < 0.0001), with similar patterns of weight loss at each interval of nonsignificant interaction (p = 0.585). Weight loss for the two groups did not differ statistically. The X-GBP group lost 5% more weight than the R-GBP group by 12 months following surgery. The adjusted average weight loss over 12 months was 56.82 kg for X-GBP and 46.82 kg for R-GBP patients. Furthermore, the X-GBP group ingested fewer calories than the R-GBP group at 3, 6, 9, and 12 months following surgery. The X-GBP group ingested a lower percentage of calories from fat than the R-GBP group at 3, 9, and 12 months following surgery. This study depicts clinical trends in weight loss following X-GBP and R-GBP surgeries. The greater weight loss of the X-GBP group may be due to differences in total caloric intake or the lower percentage of calories ingested from fat. Other possibilities for the greater weight loss shown by the X-GBP group may include changes in malabsorption or resting energy expenditure over time following surgery.

BACKGROUND: upper body, or abdominal, distribution of body fat is associated with a number of metabolic and hormonal aberrations that could influence resting energy expenditure REE. The purpose of our study was to examine the effects of fat distribution on REE of 96 morbidly obese premenopausal females. METHODS: the study population consisted of three groups of study subjects, 32 with lower body fat distribution (LBD) and waist-to-hip circumference ratios WHR < 0.80, 20 with intermediate (INT) fat distribution and WHR between 0.80 and 0.85 and 34 females with upper body distribution of fat (UBD) and WHR > 0.85. Indices measured included: (1) REE; (2) maximal oxygen consumption during an exercise tolerance test (VO&inf2; max); (3) basal respiratory quotient (RO); (4) fasting blood glucose; and (5) serum cholesterol and triglycerides. RESULTS: we found that morbidly obese women who store fat abdominally (WHR > 0.80) have significantly (p < 0.01) higher REE (kcal per h per BSA) than those with lower body obesity. Levels of triglyceride and glucose of the UBD group were also higher than those of the LBD subjects, i.e. 35% and 23%, respectively. VO&inf2; max and RO were similar between the study groups, suggesting that the elevated REE of the patients with abdominal adiposity were likely not the result of their greater muscle mass or differences in substrate utilization. CONCLUSION: fat distribution affects REE in morbidly obese premenopausal females, and further research is needed to identify the various entities regulating REE in the morbidly obese.