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 AE 15 kg among the operated patients and 0.5 AE 8.9 kg among the obese controls. After eight years the weight loss was 20 AE 16 kg in the surgical group, while the controls had gained 0.7 AE 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. International Journal of Obesity (2001) 25, Suppl 1, S2 -S4 Keywords: obesity; weight reduction; surgery; risk factors; health-related quality of lifeThe rationale behind the SOS study Obesity is associated with elevated cardiovascular risk factors, increased morbidity and mortality. 1,2 Short-term weight loss improves all risk factors. 3 However, several observational epidemiological studies have found an association between weight loss and increased, rather than decreased, mortality, even in subjects that were obese at baseline. 4 This paradox might be related to an inability to distinguish between intentional and unintentional weight loss. 5 Furthermore, some long-term trials have shown a rebound in risk factors in spite of maintained weight reduction, pointing at the need for adequate observation times. 6 Inadequate nutrient intake might make weight reduction hazardous 7 and it could also be that loss of body fat decreases, while loss of lean body mass increases mortality. 8 The SOS study was initiated in 1987 as an attempt to elucidate this apparently enigmatic situation. Long-term observation of a large cohort of well characterised obese subjects that either lose a substantial amount of weight or remain weight stable would have the ability to sort out several of these problems.Design of the SOS study SOS consists of a cross-sectional registry study and a longitudinal intervention study. 9 Obese subjects are eligible for the SOS inte...

Systematic review of long-term weight loss studies in obese adults: clinical significance and applicability to clinical practice

“…Weight loss was 28-76 kg after 2 y, [79][80][81][82][83][84][85][86][87][88][89] 17-73 kg after 3 y, [79][80][81][86][87][88][89] and 20 kg after 8 y in one study [82][83][84] based on a completers method of analysis. No study reported the proportion of subjects with Z5% weight loss, although this was probably high given the absolute weight loss with surgical therapy.…”

“…Only two studies assessed this, [82][83][84]88 thereby precluding meaningful commentary. In one study that compared surgical and nonsurgical weight loss after 8 y, the risk of type 2 diabetes was 84% less with surgery (OR ¼ 0.16; 95% CI: 0.07-0.36) but there was no effect on the risk of hypertension (OR ¼ 1.01; 95% CI: 0.61-1.67).…”

“…In one study that compared surgical and nonsurgical weight loss after 8 y, the risk of type 2 diabetes was 84% less with surgery (OR ¼ 0.16; 95% CI: 0.07-0.36) but there was no effect on the risk of hypertension (OR ¼ 1.01; 95% CI: 0.61-1.67). [82][83][84] Applicability to clinical practice. Three studies had a followup of at least 4 y.…”

“…Three studies had a followup of at least 4 y. 80,[82][83][84]89 The proportion of subjects lost to follow-up varied widely (5-42%), but was reported only in three studies. One study had a control group of 'usual care'.…”

Bariatric surgery for pediatric extreme obesity: now or later?

“…In adults, RYGB results in remission and prevention of T2DM, 104,105 with normalization of fasting hyperglycemia in 64-83% of type 2 diabetic patients and 99% of those with impaired glucose tolerance. 26,36 Improvements in insulin resistance and b-cell function have been documented following surgical weight loss.…”