Tehran Obesity Treatment Study identifies significant predictors of insufficient weight loss post-BMS

Researchers from Iran, reporting the latest outcomes from the Tehran Obesity Treatment Study, have reported older age, a higher baseline BMI, T2DM, non-smoking, and sleeve gastrectomy (SG) were significant predictors of insufficient weight loss (IWL) following BMS.

This sub analysis from TOTS, included 3,456 individuals who has BMS of whom 2,352 underwent SG, 986 underwent OAGB and 118 RYGB. IWL was defined as not achieving 50% of EWL during a median follow-up of 18 months (range: 12–24 months) after surgery or the less popular definition < 20% TWL. The individuals who did not fall into the IWL category were considered to achieve sufficient weight loss (SWL).

A majority of the 3,456 individuals (78.2%) were female and the medians of age and BMI were 39.9 years and 44.8 kg/m2, respectively. Most of the participants were categorised in the obesity class III (BMI: 40-44.9). After a median follow-up of 18 months post-surgery, 3,190 (92.3%) individuals achieved 50% or more EWL (i.e., the SWL group), and 266 (8%) failed to achieve this parameter (categorized as IWL).

The members of the IWL group were older and had a higher mean baseline BMI (47.6 ± 6.3 vs. 44.6 ± 5.5 p<0.001), as well as higher baseline FM% (51.3 ± 4.4 vs. 49.9 ± 4.7 p <0.001), and lower baseline FFM% (48.5 ± 4.1 vs. 49.9 ± 4.7% Pp<0.001). In the IWL group compared to the SWL group, a significantly higher ratio of patients underwent SG compared to GB (9.7% vs. 3.4%, p<0.001). All metabolic parameters and obesity-related comorbidities (WC, TG, FPG, HbA1C, SBP, DBP, dyslipidemia, HTN, DM, and insulin resistance) were higher or more frequent in the IWL group compared to the SWL group (p<0.05).

Figure 1 shows changes in fat mass (FM) %, fat-free mass (FFM) %, fat-free mass loss relative to weight loss (FFML/WL) %, and excess weight loss percentage (EWL) % in the SWL and IWL groups throughout a median of 18 months of follow-up. The means of FM%, FFM%, and FFML/WL% significantly decreased, and EWL% significantly increased in both the SWL and IWL groups (Ptrend < 0.05). There were significant differences in FM%, FFM%, FFML/WL%, and EWL% between the two groups over time, with the IWL group showing a higher FFM/WL% loss and a lower FM loss after six months of follow-up (P time before & after six months <0.05) (Figure 1).

Figure 1: Trend of different characteristics of IWL and SWl individuals during 24 months of follow-up. a) Fat mass percentage (FM%). b) Fat-free mass percentage (FFM%). c) fat-free mass loss/weight loss (FFML/WL). d) excess weight loss (EWL%)

With defining IWL < 50% EWL at 18 months post-surgery, an older age, suffering from T2DM, undergoing SG, a higher baseline BMI and non-smoking were associated with a greater likelihood of IWL, so these parameters were the main negative predictors of achieving a satisfactory outcome after bariatric surgery (p<0.05). In addition, by defining IWL as < 20% TWL, the prevalence of IWL and SWL was 2.9% (n=100) and 85% (n=2938), respectively. Predictors of IWL, associated with a higher risk of IWL with this definition were: an older age, suffering from DM and HTN, undergoing SG, a higher baseline BMI and non-smoking. However, significant results of hypertension and non-significant BMI of 40–44.9 kg/m2 and age of 40–59 in the multivariate analysis were different in comparison to the former definition (EWL < 50%).

Regarding the remission of co-morbidities, the analysis revealed a significantly greater remission rate of HTN and DM in the SWL group compared to the IWL. However, there were not any significant differences in dyslipidaemia resolution between the two groups.

“In order to get to the goal of effective treatment after bariatric surgery there is a dire need for a standardised definition of IWL. This makes it difficult to define how much EWL% is significant to achieve improvement of co-morbidities. Therefore, there is a need to address the IWL definitions knowledge gaps including the exact cutoff points predicting cardiometabolic outcomes,” the authors concluded. “Moreover, for obesity treatment, the term surgical nonresponse would be appropriate as a replacement for IWL. Further studies will be needed to elucidate all preoperative and post-operative modifiable predictors of IWL, including physical activity and dietary regimen, to achieve the best outcomes possible.”

The findings were reported in the paper, ‘Insufficient weight loss after bariatric surgery and its predictors: Tehran Obesity Treatment Study (TOTS)’, published inn Langenbeck's Archives of Surgery. To access this paper, please click here