Kenneth Adams

BACKGROUND: Obesity, defined by a body-mass index (BMI) (the weight in kilograms divided by the square of the height in meters) of 30.0 or more, is associated with an increased risk of death, but the relation between overweight (a BMI of 25.0 to 29.9) and the risk of death has been questioned. METHODS: We prospectively examined BMI in relation to the risk of death from any cause in 527,265 U.S. men and women in the National Institutes of Health-AARP cohort who were 50 to 71 years old at enrollment in 1995-1996. BMI was calculated from self-reported weight and height. Relative risks and 95 percent confidence intervals were adjusted for age, race or ethnic group, level of education, smoking status, physical activity, and alcohol intake. We also conducted alternative analyses to address potential biases related to preexisting chronic disease and smoking status. RESULTS: During a maximum follow-up of 10 years through 2005, 61,317 participants (42,173 men and 19,144 women) died. Initial analyses showed an increased risk of death for the highest and lowest categories of BMI among both men and women, in all racial or ethnic groups, and at all ages. When the analysis was restricted to healthy people who had never smoked, the risk of death was associated with both overweight and obesity among men and women. In analyses of BMI during midlife (age of 50 years) among those who had never smoked, the associations became stronger, with the risk of death increasing by 20 to 40 percent among overweight persons and by two to at least three times among obese persons; the risk of death among underweight persons was attenuated. CONCLUSIONS: Excess body weight during midlife, including overweight, is associated with an increased risk of death.

Despite weight loss recommendations to prevent cancer, cancer outcome studies after intentional weight loss are limited. Recently, reduced cancer mortality following bariatric surgery has been reported. This study tested whether reduced cancer mortality following gastric bypass was due to decreased incidence. Cancer incidence and mortality data through 2007 from the Utah Cancer Registry (UCR) were compared between 6,596 Utah patients who had gastric bypass (1984-2002) and 9,442 severely obese persons who had applied for Utah Driver's Licenses (1984-2002). Study outcomes included incidence, case-fatality, and mortality for cancer by site and stage at diagnosis of all gastric bypass patients, compared to nonoperated severely obese controls. Follow-up was over a 24-year period (mean 12.5 years). Total cancer incidence was significantly lower in the surgical group compared to controls (hazard ratio (HR) = 0.76; confidence interval (CI) 95%, 0.65-0.89; P = 0.0006). Lower incidence in surgery patients vs. controls was primarily due to decreased incidence of cancer diagnosed at regional or distant stages. Cancer mortality was 46% lower in the surgery group compared to controls (HR = 0.54; CI 95%, 0.37-0.78; P = 0.001). Although the apparent protective effect of surgery on risk of developing cancer was limited to cancers likely known to be obesity related, the inverse association for mortality was seen for all cancers. Significant reduction in total cancer mortality in gastric bypass patients compared with severely obese controls was associated with decreased incidence, primarily among subjects with advanced cancers. These findings suggest gastric bypass results in lower cancer risk, presumably related to weight loss, supporting recommendations for reducing weight to lower cancer risk.

BACKGROUND: Obesity is a risk factor for postmenopausal breast cancer, but the role of the timing and amount of adult weight change in breast cancer risk is unclear. METHODS: We prospectively examined the relations of adiposity and adult weight change to breast cancer risk among 99 039 postmenopausal women in the National Institutes of Health-AARP Diet and Health Study. Anthropometry was assessed by self-report in 1996. Through 2000, 2111 incident breast cancer cases were ascertained. RESULTS: Current body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared), BMI at ages 50 and 35 years, and waist-hip ratio were associated with increased breast cancer risk, particularly in women not using menopausal hormone therapy (MHT). Weight gained between age 18 years and the current age, between ages 18 and 35 years, between ages 35 and 50 years, and between age 50 years and the current age was consistently associated with increased breast cancer risk in MHT nonusers (relative risk [RR], 2.15; 95% confidence interval [CI], 1.35-3.42 for a >/=50-kg weight gain between age 18 years and the current age vs stable weight) but not in current MHT users. Risk associated with adult weight change was stronger in women with later vs earlier age at menarche (RR, 4.20; 95% CI, 2.05-8.64 for >/=15 years vs RR, 1.51; 95% CI, 1.11-2.06 for 11-12 years; P = .007 for interaction). In MHT nonusers, the associations with current BMI and adult weight change were stronger for advanced disease than for nonadvanced disease (P = .009 [current BMI] and .21 [weight gain] for heterogeneity) and were stronger for hormone receptor-positive than hormone receptor-negative tumors (P < .001 for heterogeneity). CONCLUSION: Weight gain throughout adulthood is associated with increased postmenopausal breast cancer risk in MHT nonusers.

The authors examined the association between waist circumference and mortality among 154,776 men and 90,757 women aged 51-72 years at baseline (1996-1997) in the NIH-AARP Diet and Health Study. Additionally, the combined effects of waist circumference and body mass index (BMI; weight (kg)/height (m)(2)) were examined. All-cause mortality was assessed over 9 years of follow-up (1996-2005). After adjustment for BMI and other covariates, a large waist circumference (fifth quintile vs. second) was associated with an approximately 25% increased mortality risk (men: hazard ratio (HR) = 1.22, 95% confidence interval (CI): 1.15, 1.29; women: HR = 1.28, 95% CI: 1.16, 1.41). The waist circumference-mortality association was found in persons with and without prevalent disease, in smokers and nonsmokers, and across different racial/ethnic groups (non-Hispanic Whites, non-Hispanic Blacks, Hispanics, and Asians). Compared with subjects with a combination of normal BMI (18.5-<25) and normal waist circumference, those in the normal-BMI group with a large waist circumference (men: > or =102 cm; women: > or =88 cm) had an approximately 20% higher mortality risk (men: HR = 1.23, 95% CI: 1.08, 1.39; women: HR = 1.22, 95% CI: 1.09, 1.36). The finding that persons with a normal BMI but a large waist circumference had a higher mortality risk in this study suggests that increased waist circumference should be considered a risk factor for mortality, in addition to BMI.

Renal cell cancer (RCC) incidence has increased in the United States over the past three decades. The authors analyzed the association between body mass index (BMI) and invasive RCC in the National Institutes of Health (NIH)-AARP Diet and Health Study, a large, prospective cohort aged 50-71 years at baseline initiated in 1995-1996, with follow-up through December 2003. Detailed analyses were conducted in a subcohort responding to a second questionnaire, including BMI at younger ages (18, 35, and 50 years); weight change across three consecutive age intervals; waist, hip, and waist-to-hip ratio; and height at age 18 years. Incident RCC was diagnosed in 1,022 men and 344 women. RCC was positively and strongly related to BMI at study baseline. Among subjects analyzed in the subcohort, RCC associations were strongest for baseline BMI and BMI recalled at age 50 years and were successively attenuated for BMI recalled at ages 35 and 18 years. Weight gain in early (18-35 years of age) and mid- (35-50 years of age) adulthood was strongly associated with RCC, whereas weight gain after midlife (age 50 years to baseline) was unrelated. Waist-to hip ratio was positively associated with RCC in women and with height at age 18 years in both men and women.