Obesity Abstracts

Background: Resting energy expenditure (REE) and diet induced thermogenesis (DIT) are known to influence long term maintenance of weight loss following bariatric surgery. Although it is known that fat free mass (FFM) contributes to REE to a greater extent than fat mass (FM), there has been relatively little work looking at the REE:FFM ratio and its overall effect on and relationship to weight loss.

Aim: To assess weight loss, REE and REE:MMT ratio in patients undergoing Roux-en-Y Gastric Bypass (RYGB) up to one year post-operatively.

Methods: 20 patients undergoing RYGB were followed up for one year. Weight, REE and FFM were measured at baseline (pre operatively), 1, 3, 6 and 12 months using the Tanita BC-418MA body composition analyser. One way ANOVA was used to compare results at 1, 3, 6 and 12 months to baseline.

Results: There were 16 females and 5 males. Mean age was 48. Overall mean weight (kg) decreased significantly over the course of one year (117.8 kg vs 80.6 kg P=<0.0001). Mean REE decreased significantly at all times points compared to baseline (2037 kcal at baseline vs 1583 kcal at 12 months). DIT increased at 3 months compared to baseline and then decreased at one year (229.5 kcal vs 354.7 kcal vs 263.3 kcal respectively) however this difference was not significant. FFM decreased significantly from baseline to 12 months (P=<0.0001). REE:FFM ratio decreased significantly at 3 and 6 months compared to baseline (P=0.028), there was no significant difference at 12 months (P=0.215).

Conclusion: Our findings indicate a decrease in weight, REE and FFM over 12 months in RYGB patients. REE:FFM ratio was also significantly decreased at 3 and 6 months. This suggests that the reduction in REE may either be independent of FFM (i.e. another factor is contributing to REE decrease) or the inherent metabolic activity of the FFM in these post-operative patients has decreased. Further studies are required to investigate the relationship of FFM to REE and weight loss.