Magnitude and composition of post-MBS weight loss not associated with MACE

The magnitude and composition of post- metabolic-bariatric surgery (MBS) weight loss were not associated with incident major adverse cardiovascular events (MACE) and mortality in the total population, according to an international team of researchers.

They also reported that a high total weight loss and a disproportional composition of weight loss with a relatively high fat-free mass loss, were associated with a greater risk of adverse outcomes in middle-aged and older patients.

Although previous studies have shown that MBS is associated with a reduced risk of all-cause and cardiovascular mortality and a lower incidence of heart failure, myocardial infarction and stroke, the researchers said it remains unclear how these risk reductions are impacted by the composition of weight loss, more specifically by disproportional FFM loss.

They hypothesised that a lower fat mass (FM) loss and a higher (proportional) free-fat mass (FFM) loss are associated with a higher incidence of events. Therefore, they investigated the association between the magnitude and composition of post-MBS weight loss and the incidence of major adverse cardiovascular events and all-cause mortality during clinical follow-up.

This retrospective cohort study, a total of 892 out of 6,781 eligible patients were excluded due to failure to match data of the NOK with hospital patient files (n=66), type of surgery (n = 98) and missing data for body composition (n=728). The analytical cohort consisted of 5,889 patients (21% men), who underwent RYGB (84%) or SG (16%) at the age of 44.3 ± 11.1 years and with a preoperative BMI of 44.3 ± 5.7 kg/m2. Preoperative medication use was 22% for cardiovascular medication and 15% for diabetes medication. Mean follow-up time was 4.9 ± 2.2 years.

Outcomes

At 12.3 ± 0.9 months post-surgery, patients had lost 42.6 ± 11.7 kg weight, which was equivalent to 33.0% ± 7.1% TWL. Weight loss consisted of 30.6 ± 11.2 kg FM and 9.5 ± 5.6 kg FFM, yielding a FFML/WL of 22.5% ± 12.1%. Eighteen percent of the patients showed a FFML/WL ≥ 30%, whereas the cut points for HI versus LO-MO were established for TWL (≥ 36.2%), FML (≥ 33.9 kg) and FFML (≥ 10.8 kg). The prevalence of obesity complications, cardiovascular- and diabetes medication was higher among patients with LO-MO %TWL and %FFML/WL ≥ 30%.

After nine years of follow-up, 106 patients (3.7 per 1000 person years) experienced the composite endpoint of MACE or all-cause mortality (n=62 and n=44, respectively). No significant differences in event-free survival between %TWL groups (event rate: LO-MO 1.9% vs. HI 1.5%, p=0.49), FML groups (event rate: LO-MO 2.0% vs. HI 1.4%, p=0.07) and FFML groups (event rate: LO-MO 1.8% vs. HI 1.8%, p=0.70) were observed, however patients with a FFML/WL ≥ 30% (event rate: LO-MO 1.5% vs. HI 3.2%, p=0.006) had a significantly worse survival. After adjustment for potential confounders, no significant associations were observed between weight loss composition subgroups and clinical outcomes.

High TWL and FFML/WL ≥ 30% were associated with an increased risk of MACE or mortality in patients aged ≥ 45 years (fully adjusted HR = 1.68 [1.03–2.75] and HR = 1.78 [1.12–2.85], respectively), whereas no impact of age was observed for FML (kg) and FFML (kg). No associations between the composite endpoint and any of the body composition outcomes were found for strata based on sex, type of surgery and cardiovascular or diabetes medication use.

“These findings contradict the current belief that more weight loss is better, and future studies should examine the potential harm of excessive TWL and evaluate countermeasures to limit disproportional FFML in order to improve clinical outcomes for patients undergoing MBS,” they concluded. “It is important to take patient (i.e., age, gender, health status) and characteristics (i.e., type of surgery, perioperative care program) into account in such endeavours.”

The findings were reported in the paper, 'Association of Weight Loss Composition Following Metabolic-Bariatric Surgery With Incident Major Adverse Cardiovascular Events and All-Cause Mortality', published in Clinical Obesity. To access this paper, please click here