The morbidity and mortality associated with overweight and obesity in adulthood: a systematic review.

BACKGROUND Overweight and obesity are generally thought to elevate morbidity and mortality. New data call this supposed association into question. METHODS The Cochrane, Pubmed, and other databases were systematically searched for a combination of relevant terms and subject headings. Meta-analyses and cohort studies based on the German population were evaluated for possible associations between overweight/ obesity and adult morbidity and mortality. Case-control and cross-sectional studies were excluded. RESULTS A total of 27 meta-analyses and 15 cohort studies were evaluated. The overall mortality of overweight persons (body mass index [BMI] 25-29.9 kg/m(2)) is no higher than that of persons of normal weight (BMI 18.5-24.9 kg/m(2)), but their mortality from individual diseases is elevated, diminished or unchanged, depending on the particular disease. The overall morbidity is unknown. Both obesity (BMI >30 kg/m(2)) and overweight are associated with increased disease-specific morbidity for some diseases, but decreased or unchanged for others. In general, obesity confers a higher risk than overweight. Morbidity and mortality are markedly influenced by the patient's age, sex, ethnic origin, and social status. The external validity of the comparative predictive performance (c-statistic) of BMI, waist circumference, and ratio of waist to hip circumference cannot be determined from the available analyses. CONCLUSION The prevailing notion that overweight increases morbidity and mortality, as compared to so-called normal weight, is in need of further specification. Obesity, however, is indeed associated with an elevated risk for most of the diseases studied.