Underweight, overweight, and obese men and women had higher rates of death than men and women of normal weight. The association of BMI with death varied according to the cause of death and was modified by age, sex, and smoking history.

Obesity is associated with diverse health risks, but the role of body weight (BMI) as a risk factor for all and site-specific cancers remains controversial and risks for cancer associated with obesity have not been well-characterized in Asians. Body weight and risk for cancer were examined in a 14-year prospective cohort study of 1,213,829 Koreans aged 30-95 years insured by the National Health Insurance Corporation who had a biennial medical evaluation in 1992-1995. Incidence rates for all cancers and site-specific cancers were examined in relation to BMI. Age- and smoking-status adjusted hazard ratios (HR) with 95% confidence intervals (CI) were examined using the Cox proportional hazards model. For both sexes, the average baseline BMI was 23.2 kg/m(2), and the association of risk for all-cancers with BMI was positive. Obese men (BMI >or= 30 kg/m(2)) were at increased risk for developing the following cancers: stomach (1.31, 1.05-1.64), colon (1.42, 1.02-1.98), liver (1.63, 1.27-2.10) and gallbladder (1.65, 1.11-2.44). Obese women (BMI >or= 30 kg/m(2)) were at increased risk for developing liver cancer (1.39, 1.00-1.94), pancreatic cancer (1.80, 1.14-2.86) and breast cancer among women aged >or=50 years old (1.38, 1.00-1.90). The HRs were comparable in never and ever smokers for all cancers and all specific sites except for lung cancer. For all cancers common to both sexes, the association was significantly weaker (p < 0.01) in females. Our study provides further confirmation of the excess cancer risk associated with obesity. Rising obesity in Asian populations raises concern that increasing numbers of avoidable cancer cases will occur among Asians.

In Korea, smoking is an independent risk factor for a number of major cancers. The findings affirm the need for aggressive tobacco control in Korea in order to minimize the epidemic of smoking-caused disease.

Cigarette smoking, heavy alcohol consumption, and HBsAg were independently associated with increased risk of mortality from hepatocellular carcinoma but did not interact synergistically. The relatively higher increase in mortality from hepatocellular carcinoma in HBsAg-seropositive women compared with men merits further research.

Background: Despite differences in body shape and adiposity characteristics according to sex and age, a single range of healthy weight [body mass index (BMI, kg/m2) of 18.5–24.9) regardless of sex and age has been recommended. The aim of the study is to examine whether the association between BMI and all-cause mortality varies by sex and age, and, if relevant, to estimate sex-age-specific optimal BMIs associated with a minimal risk of death.Methods: A total of 12 832 637 Korean adults aged 18–99 years who participated in health examinations during 2001–04 were followed up until 2013. Hazard ratios of death in sex-age groups were calculated using Cox regression models after adjustment for age, smoking status and known pre-existing illness.Results: During follow-up, 456 175 men and 241 208 women died. Among men, the age-specific optimal BMI was 23.0–25.9 (kg/m2) at 18–34 years, 24.0–27.9 at 45–54 year, and 25.0–28.9 at 65–74 years. Among women, it was 15.5–24.9 at 18–34 years, 21.0–26.9 at 45–54 years and 24.0–28.9 at 65–74 years. Patterns of sex-age-specific association generally did not differ between never-smokers with no known illness and all participants. Progressively increased risks above and below sex-age-specific optimums were observed (reverse J-curve). Smoking had a limited impact on the observed associations.Conclusions: Women had a lower optimal BMI than men, especially at younger ages. The optimal BMI increased with age. Change in optimal BMI with age, however, was more profound in women than in men. Sex-age-specific optimums were generally higher than the current normal weight (BMI of 18.5–24.9), except in women below 50 years. Sex-age-specific guidelines related to body weight may be needed to guide people for better health.