Impact of weight change, secular trends and ageing on cardiovascular risk factors: 10-year experiences from the SOS study.

OBJECTIVE: Many short-term studies indicate that 5% weight loss in the obese is enough to induce significant improvements of cardiovascular risk factors. However, it is not known what degree of weight loss is required to improve risk factors over a more extended period of time or how ageing and secular trends per se are influencing risk factors during long-term follow-up.
METHODS: Patients examined after 10 years in the intervention study Swedish Obese Subjects were used for the current analysis. Surgically treated subjects (n=959) and conventionally treated obese controls (n=842) were pooled to obtain a study group with a large range of weight changes. The patients were divided in 11 groups based on the amount of weight change. Analysis of covariance was used to determine the necessary weight change over 10 years for a significant alteration of a risk factor. In a linear regression of risk factor change by weight change, the y intercept was interpreted as the effect of 10 years ageing and secular trends on a given risk factor in the absence of weight change.
RESULTS: The necessary weight loss for significant improvement of risk factors ranged from 10 to 44 kg. At zero weight change, 10 years of ageing was associated with significant increases in systolic blood pressure, pulse pressure, high-density lipoprotein cholesterol and glucose, and with significant decreases in diastolic blood pressure, total cholesterol, triglycerides and insulin.
CONCLUSIONS: The necessary weight loss to maintain a favourable effect on risk factors in an obese population is larger than previously indicated by short-term studies. Treatment effects are influenced by non-weight change-dependant shifts in risk factor levels.