Health outcomes and their association with weight regain after substantial weight loss in Sweden: a prospective cohort study

Abstract

Background: The clinical implications of weight regain following weight loss remain uncertain. We analysed mortality, cardiovascular events, cancer, and microvascular disease in individuals with significant weight loss, comparing maintainers to regainers.

Methods: Using a prospective cohort design, we analysed 1346 participants who underwent bariatric surgery in the Swedish Obese Subjects (SOS) study, aged 37-60 years with BMI ≥34 (men) or ≥38 (women), recruited 1987-2001. Individuals who regained ≥20% of their 1-year weight loss after 4 years (regain group) were compared to those who regained less (maintenance group). The study was closed on December 31, 2020 with median follow-up of 27 years and 99.9% mortality tracking (ClinicalTrials.govNCT01479452).

Findings: Average weight loss after 1 year was 29.3 ± 11.7 kg and 31.9 ± 13.8 kg and average weight change from year 1 to year 4 was +12.7 ± 6.6 kg and -0.6 ± 7.3 kg in the regain and maintenance groups, respectively. During follow-up, regain and maintenance groups showed similar rates of total mortality and cancer, 12.4 (95% CI: 10.9-14.2) vs 12.4 (10.7-14.3), p = 0.740, and 11.3 (95% CI: 9.7-13.0) vs 10.4 (8.8-12.2) per 1000 person-years (p = 0.308), respectively. The regain group had, however, higher incidence of microvascular disease, 11.0 (95% CI: 9.5-12.8) vs 8.7 (7.3-10.4) per 1000 person-years (p = 0.024), and while not statistically significant, also higher incidence of major adverse cardiovascular events (myocardial infarction, stroke, and heart failure) 15.7 (95% CI: 13.8-17.8) vs 13.0 (11.2-15.1) per 1000 person-years (p = 0.055).

Interpretation: Weight regain was linked to increased vascular disease risk but we could not demonstrate an association with life expectancy.

Funding: The Swedish Research Council, the Swedish State under the agreement between the Swedish Government and the county councils, the Health & Medical Care Committee of the Region Västra Götaland, the Adlerbert Research Foundation, the Wilhelm and Martina Lundgren Foundation, the Royal Society of Arts and Sciences in Gothenburg, Academy of Finland, Finnish Medical Foundation, Gyllenberg Foundation, Novo Nordisk Foundation, Finnish Diabetes Research Foundation, Paulo Foundation and Sigrid Juselius Foundation.

Keywords: Bariatric surgery; Morbidity; Mortality; Obesity; Weight regain.

Fig. 1

Changes in body mass index, both absolute (A) and relative (B), over 20 years following bariatric surgery for the weight regain and weight maintenance groups. The comparison between the regain and the maintenance group was adjusted for age and sex.

Fig. 2

Self-reported energy intake (A), leisure-time physical activity (B), and work-related physical activity (C) in the weight regain and weight maintenance groups over 10 years following bariatric surgery. The comparisons between the regain and the maintenance group were adjusted for age and sex.

Fig. 3

Kaplan–Meier cumulative incidence of major adverse cardiovascular events (myocardial infarction, stroke and heart failure) (A), cancer (B), and microvascular disease (C) in the weight regain and maintenance groups after bariatric surgery, including both fatal and non-fatal events. The comparisons between the regain and the maintenance group were adjusted for age, sex, BMI, smoking status, diabetes, history of cardiovascular disease, year of inclusion to the study, and the type of surgery. Individuals with an event during the first four years were excluded from the respective outcome analysis.

Fig. 4

Survival in weight regain and maintenance groups. Shown are the Kaplan–Meier estimate of survival (opaque lines) and the estimate of survival from an unadjusted Gompertz regression model (fainter lines).