The Swedish Obese Subjects (SOS) study—rationale and results

Abstract

OBJECTIVE: Obesity is associated with increased morbidity and mortality. Several observational epidemiological studies have indicated that weight gain and weight loss, even in the obese, is also related to an increased mortality. The Swedish Obese Subjects (SOS) study was initiated in 1987 as an attempt to elucidate this paradox.

Design: Two thousand matched patient pairs will be followed for 10 y each. One pair member is surgically treated, while the other receives conventional obesity treatment. By February 2000, 1879 patient pairs have been recruited.

RESULTS: The two-y weight reduction was 28±15 kg among the operated patients and 0.5±8.9 kg among the obese controls. After eight years the weight loss was 20±16 kg in the surgical group, while the controls had gained 0.7±12 kg. Weight reductions achieved in the surgical group reduced the two-y incidence of diabetes 32 times as compared to the controls. After eight years there was still a 5-fold reduction in diabetes incidence. The two-y incidence of hypertension was similarly reduced 2.6 times in the surgical group. After eight years the incidence of hypertension was almost equal in the two study groups.

CONCLUSION: Compared to weight stability, large intentional weight loss results in substantial reductions in the two-y incidence of several cardiovascular risk factors. After eight years there is still a reduced risk of developing diabetes in the surgical group, while the incidence of hypertension is equal in the two treatment groups. Whether intentional weight loss will reduce mortality is still too early to tell.