The Relation of Body Mass Index,Cardiorespiratory Fitness,and All‐Cause Mortality in Women

Objective: To examine the relation of body mass index (BMI), cardiorespiratory fitness (CRF), and all‐cause mortality in women. Research Methods and Procedures: A cohort of women (42.9 ± 10.4 years) was assessed for CRF, height, and weight. Participants were divided into three BMI categories (normal, overweight, and obese) and three CRF categories (low, moderate, and high). After adjustment for age, smoking, and baseline health status, the relative risk (RR) of all‐cause mortality was determined for each group. Further multivariate analyses were performed to examine the contribution of each predictor (e.g., age, BMI, CRF, smoking status, and baseline health status) on all‐cause mortality while controlling for all other predictors. Results: During follow‐up (113,145 woman‐years), 195 deaths from all causes occurred. Compared with normal weight (RR = 1.0), overweight (RR = 0.92) and obesity (RR = 1.58) did not significantly increase all‐cause mortality risk. Compared with low CRF (RR = 1.0), moderate (RR = 0.48) and high (RR = 0.57) CRF were associated significantly with lower mortality risk (p = 0.002). In multivariate analyses, moderate (RR = 0.49) and high (RR = 0.57) CRF were strongly associated with decreased mortality relative to low CRF (p = 0.003). Compared with normal weight (RR = 1.0), overweight (RR = 0.84) and obesity (RR = 1.21) were not significantly associated with all‐cause mortality. Discussion: Low CRF in women was an important predictor of all‐cause mortality. BMI, as a predictor of all‐cause mortality risk in women, may be misleading unless CRF is also considered.     

Eligibility for Obesity Treatment and Risk of Mortality in Men

Objective: To evaluate the risk of all‐cause and cardiovascular disease (CVD) mortality associated with each outcome of the NIH obesity treatment algorithm and to examine the effects of cardiorespiratory fitness on the risk of mortality associated with these outcomes. Research Methods and Procedures: The NIH obesity treatment algorithm was applied to 18, 666 men (20 to 64 years of age) from the Aerobics Center Longitudinal Study in Dallas, TX, examined between 1979 and 1995. Risk of all‐cause and CVD mortality was assessed using Cox proportional hazards regression. Results: A total of 7029 men (37.7%) met the criteria for needing weight loss treatment [overweight (BMI = 25 to 29.9 kg/m² or WC > 102 cm) with ≥2 CVD risk factors or obese (BMI ≥ 30 kg/m²)]. Mortality surveillance through 1996 identified 435 deaths (151 from CVD) during 191, 364 man‐years of follow‐up. Compared with the normal weight reference group, the hazard ratios (95% confidence interval) for death from all causes were 0.63 (0.45 to 0.88), 1.23 (0.98 to 1.54), 1.05 (0.60 to 1.85), and 1.71 (1.64 to 2.31) for men who were overweight with <2 CVD risk factors, overweight with ≥2 CVD risk factors, obese with <2 CVD risk factors, and obese with ≥2 CVD risk factors, respectively. Corresponding hazard ratios for CVD mortality were 0.72 (0.38 to 1.37), 1.67 (1.12 to 2.50), 1.69 (0.67 to 4.30), and 3.31 (2.07 to 5.30). Including physical fitness as a covariate significantly attenuated all risk estimates. Discussion: The NIH obesity treatment algorithm is useful in identifying men at increased risk of premature mortality; however, including an assessment of fitness would help improve risk stratification among all groups of patients.     

Body Mass Index and All-Cause Mortality in a Large Prospective Cohort of White and Black U.S. Adults

Remaining controversies on the association between body mass index (BMI) and mortality include the effects of smoking and prevalent disease on the association, whether overweight is associated with higher mortality rates, differences in associations by race and the optimal age at which BMI predicts mortality. To assess the relative risk (RR) of mortality by BMI in Whites and Blacks among subgroups defined by smoking, prevalent disease, and age, 891,572 White and 38,119 Black men and women provided height, weight and other information when enrolled in the Cancer Prevention Study II in 1982. Over 28 years of follow-up, there were 434,400 deaths in Whites and 18,702 deaths in Blacks. Cox proportional-hazards regression was used to estimate multivariable-adjusted relative risks (RR) and 95% confidence intervals (CI). Smoking and prevalent disease status significantly modified the BMI-mortality relationship in Whites and Blacks; higher BMI was most strongly associated with higher risk of mortality among never smokers without prevalent disease. All levels of overweight and obesity were associated with a statistically significantly higher risk of mortality compared to the reference category (BMI 22.5–24.9 kg/m²), except among Black women where risk was elevated but not statistically significant in the lower end of overweight. Although absolute mortality rates were higher in Blacks than Whites within each BMI category, relative risks (RRs) were similar between race groups for both men and women (p-heterogeneity by race  = 0.20 for men and 0.23 for women). BMI was most strongly associated with mortality when reported before age 70 years. Results from this study demonstrate for the first time that the BMI-mortality relationship differs for men and women who smoke or have prevalent disease compared to healthy never-smokers. These findings further support recommendations for maintaining a BMI between 20–25 kg/m² for optimal health and longevity.     

Cut‐off Point of BMI and Obesity‐Related Comorbidities and Mortality in Middle‐Aged Koreans

Objective: The need for a lower BMI to classify overweight in Asian populations has been controversial. Using both disease and mortality outcomes, we investigated whether lower BMI cut‐off points are appropriate for identifying increased health risk in Koreans. Research Methods and Procedures: We conducted a cohort study among 773, 915 men and women from 30 to 59 years old with 8‐ to 10‐year follow‐up periods. Primary outcomes were change of obesity prevalence, obesity‐related disease incidence, and all‐cause mortality. Results: Prevalence of overweight (BMI of 25.0‐29.9) has steadily increased (1.3% annually), whereas obesity (BMI ≥ 30) showed a lower prevalence and only a slight increase (0.1%‐0.2% annually). Our study revealed that dose‐response relationships exist between obesity and related disease incidences (hypertension, type 2 diabetes, and hypercholesterolemia) beginning at lower BMI levels than previously reported. Compared with those in the healthy weight range, Koreans with a BMI ≥ 25 were not at greater risk of hypertension, type 2 diabetes, or hypercholesterolemia than has been reported for whites in similar studies. Obesity‐related all‐cause mortality also did not seem so different from that of whites. Discussion: Our findings did not support the use of a lower BMI cut‐off point for defining overweight in Koreans compared with whites for the purpose of identifying different risks. However, populations with BMI ≥ 25 are rapidly increasing and have substantial risks of diseases. To preempt the rapid increases in obesity and related health problems that are occurring in Western countries, Korea should consider using a BMI of 25 as an action point for obesity prevention and control interventions.     

Waist Circumference,BMI, Smoking,and Mortality in Middle‐Aged Men and Women

Objective: Measurement of waist circumference alone as a proxy of abdominal fat mass has been suggested as a simple clinical alternative to BMI for detecting adults with possible health risks due to obesity. Research Methods and Procedures: From 1993 to 1997, 27, 178 men and 29, 875 women, born in Denmark, 50 to 64 years of age, were recruited in the Danish prospective study Diet, Cancer and Health. By the end of the year 2000, 1465 deaths had occurred. We evaluated the relationship between waist circumference and BMI (simultaneously included in the model) and all‐cause mortality. We used Cox regression models to estimate the mortality‐rate ratios and to consider possible confounding from smoking. Results: Waist circumference among both men and women showed a strong dose‐response type of relationship with mortality when adjusted for BMI, whereas the low range of BMI was inversely associated with mortality when adjusted for waist circumference. A 10% larger waist circumference corresponded to a 1.48 (95% confidence interval: 1.36 to 1.61) times higher mortality over the whole range of waist circumference. The associations were independent of age and time since baseline examination. Restriction to never smokers showed a similar pattern, but a weakening of the associations. Discussion: Despite the high correlation between waist circumference and BMI, the combination may be very relevant in clinical practice because waist circumference for given BMI was a strong predictor of all‐cause mortality. The inverse association between BMI and mortality for given waist circumference was diminished in never smokers, particularly for high values of BMI.     

Association of cigarettes smoked daily with obesity in a general adult population

Objective: We analyzed the cross‐sectional association between obesity and smoking habits, taking into account diet, physical activity, and educational level. Research Methods and Procedures: We used data from the 2002 Swiss Health Survey, a population‐based cross‐sectional telephone survey assessing health and self‐reported health behaviors. Reported smoking habits, height, and weight were available for 17,562 subjects (7844 men and 9718 women) ≥25 years of age. BMI was calculated as (self‐reported) weight divided by height². Results: Mean BMI was 25.1 kg/m² for non‐smokers, 26.1 kg/m² for ex‐smokers, 24.6 kg/m² for light smokers (1 to 9 cigarettes/d), 24.8 kg/m² for moderate smokers (10 to 19 cigarettes/d), and 25.3 kg/m² for heavy smokers (≥20 cigarettes/d) in men and 24.0, 24.1, 22.9, 22.9, and 23.3 kg/m², respectively, in women. Obesity (BMI ≥ 30 kg/m²) was increasingly frequent with older age, lower physical activity, lower fruits/vegetables intake, and lower educational level. Compared with non‐smokers, the odds ratio for obesity vs. normal weight (BMI = 18.5 to 25.0 kg/m²) adjusted for age, nationality, educational level, leisure time physical activity, and fruit/vegetable intake were 1.9 (95% confidence interval: 1.5 to 2.3) for ex‐smokers, 0.5 (0.3 to 0.8) for light smokers, 0.7 (0.4 to 1.0) for moderate smokers, and 1.3 (1.0 to 1.7) for heavy smokers in men and 1.3 (1.1 to 1.6), 0.7 (0.5 to 1.0), 0.8 (0.5 to 1.0), and 1.1 (0.8 to 1.4), respectively, in women. Discussion: Among smokers, obesity was associated in a graded manner with the number of cigarettes daily smoked, particularly in men. More emphasis should be put on the risk of obesity among smokers.     

Morbidity and mortality risk associated with an overweight BMI in older men and women

Background: There is controversy as to whether older adults with a BMI in the overweight range (25 to 29.9 kg/m²) are at increased health risk and whether they should be encouraged to lose weight. The purpose of this study was to determine whether older adults with a BMI in the overweight range are at increased morbidity and mortality risk. Methods: Participants consisted of 4968 older (≥65 years) men and women from the Cardiovascular Health Study limited access dataset. Based on BMI (kg/m²), participants were grouped into normal‐weight (20 to 24.9 kg/m²), overweight (25 to 29.9 kg/m²), and obese (≥30 kg/m²) categories. Participants were followed for up to 9 years to determine if they developed 10 weight‐related health outcomes that are pertinent to older adults. Cox proportional hazards models were used to estimate the hazards ratios of morbidity and mortality after adjusting for age, sex, income, smoking, and physical activity. Results: Compared with the normal‐weight group, the risks of myocardial infarction, stroke, sleep apnea, urinary incontinence, cancer, and osteoporosis were not different in the overweight group (p > 0.05). The risks for arthritis and physical disability were modestly increased in the overweight group (p < 0.05), whereas the risk for type 2 diabetes was increased by 78% in the overweight group (p < 0.01). After adjusting for all relevant covariates, all‐cause mortality risk was 11% lower in the overweight group (p < 0.05). Conclusions: A BMI in the overweight range was associated with some modest disease risks but a slightly lower overall mortality rate. These findings suggest that a BMI cut‐off point of 25 kg/m² may be overly restrictive for the elderly.     

Estimating the Effects of Obesity and Weight Change on Mortality Using a Dynamic Causal Model

Background

A well-known challenge in estimating the mortality risks of obesity is reverse causality attributable to illness-associated and smoking-associated weight loss. Given that the likelihood of chronic and acute illnesses rises with age, reverse causality is most threatening to estimates derived from elderly populations.

Methods

I analyzed data from 12,523 respondents over 50 years old from a nationally representative longitudinal dataset, the Health and Retirement Study (HRS). The effects of both baseline body weight and time-varying weight change on mortality are estimated, adjusting for demographic and socio-economic variables, as well as time-varying confounders including illness and smoking. Body weight is measured by body mass index (BMI). In survival models for mortality, illness and smoking were lagged to minimize bias from reverse causality in estimates of the effect of weight change. Furthermore, because illness both causes and is caused by changes in BMI, I used a marginal structural model (MSM) rather than standard adjustment to control confounding by this and other time-dependent factors.

Results

Overall, relative to normal weight, underweight and Class II/III at baseline are associated with hazard ratios that are 2.07 (95% confidence interval (CI): 1.28–3.37) and 1.82 (1.54–2.16) respectively, whereas overweight and Class I obesity do not significantly lower or raise the mortality risks. Furthermore, relative to stable weight change, all types of weight change lead to significantly increased risk of mortality. Specifically, large weight loss results in a mortality risk that is nearly 3.86 (3.26–4.58) times of staying in the stable weight range and small weight loss is about 1.81 (1.55–2.11 ) times riskier. In contrast, large weight gain and small weight gain are associated with hazard ratios that are 1.98 (1.67–2.35) and 1.20 (1.02–1.41) respectively.

Conclusions

Being underweight or severe obese at baseline is associated with excess mortality risk, and weight change tend to raise mortality risk. Both the confounding by illness and by smoking lead to overestimates of the effects of being underweight at baseline and of weight loss, but underestimates the effect of being obese at baseline.     

Comparison of Overall Obesity and Body Fat Distribution in Predicting Risk of Mortality

Results of studies comparing overall obesity and abdominal adiposity or body fat distribution with risk of mortality have varied considerably. We compared the relative importance and joint association of overall obesity and body fat distribution in predicting risk of mortality. Participants included 5,799 men and 6,429 women aged 30–102 years enrolled in the third National Health and Nutrition Examination Survey who completed a baseline health examination during 1988–1994. During a 12‐year follow‐up (102,172 person‐years), 1,188 men and 925 women died. In multivariable‐adjusted analyses, waist‐to‐thigh ratio (WTR) in both sexes (P_trend <0.01 for both) and waist‐to‐hip ratio (WHR) in women (P_trend 0.001) were positively associated with mortality in middle‐aged adults (30–64 years), while BMI and waist circumference (WC) exhibited U‐ or J‐shaped associations. Risk of mortality increased with a higher WHR and WTR among normal weight (BMI 18.5–24.9 kg/m²) and obese (BMI ≥30.0 kg/m²) adults. In older adults (65–102 years), a higher BMI in both sexes (P_trend <0.05) and WC in men (P_trend 0.001) were associated with increased survival, while remaining measures of body fat distribution exhibited either no association or an inverse relation with mortality. In conclusion, ratio measures of body fat distribution are strongly and positively associated with mortality and offer additional prognostic information beyond BMI and WC in middle‐aged adults. A higher BMI in both sexes and WC in men were associated with increased survival in older adults, while a higher WHR or WTR either decreased or did not influence risk of death.     

Prevalence of Overweight and Obesity in Elderly People in Spain

Objective: To estimate the prevalence of obesity and overweight in the older adult population in Spain by sex, age, and educational level. Research Methods and Procedures: A cross‐sectional study was carried out in 2001 in a sample of 4009 persons representative of the noninstitutionalized population ≥60 years of age. Anthropometric measurements (BMI and waist circumference) were obtained using standardized techniques and equipment. Overweight was considered at a BMI of 25 to 29.9 kg/m² and obesity at a BMI of ≥30 kg/m². Central obesity was considered at a waist circumference of >102 cm in men and >88 cm in women. Results: The mean BMI was 28.2 kg/m² in men and 29.3 kg/m² in women. The prevalence of overweight and obesity in men was 49% and 31.5%, respectively. The corresponding percentages in women were 39.8% and 40.8%. The prevalence of obesity was higher in persons with no education than in those with third level education (i.e., university studies), especially among women (41.8% vs. 17.5%). The prevalence of central obesity was 48.4% in men and 78.4% in women. Differences by educational level were seen in only women, in whom the prevalence of central obesity was 80.9% in those with no education and 59% in those with third‐level education. Discussion: The prevalence of overweight and obesity in the Spanish adult elderly population is very high. Some other populations show similar prevalences, especially in Mediterranean countries. Socioeconomic conditions in Spain during the years these cohorts were born may partly explain the high‐frequency of obesity.     

Dietary Intake of Whole and Refined Grain Breakfast Cereals and Weight Gain in Men

Objective: Prospective studies have suggested that substituting whole grain for refined grain products may lower the risk of overweight and obesity. Breakfast cereal intake is a major source of whole and refined grains and has also been associated with having a lower BMI. The aim of this study was to prospectively assess the association between whole and refined grain breakfast cereal intakes and risk of overweight (BMI ≥ 25 kg/m²) and weight gain. Research Methods and Procedures: We examined 17, 881 U.S. male physicians 40 to 84 years of age in 1982 who were free of cardiovascular disease, diabetes mellitus, and cancer at baseline and reported measures of breakfast cereal intake, weight, and height. Results: Over 8 and 13 years of follow‐up, respectively, men who consumed breakfast cereal, regardless of type, consistently weighed less than those who consumed breakfast cereals less often (p value for trend = 0.01). Whole and refined grain breakfast cereal intake was inversely associated with body weight gain over 8 years, after adjustment for age, smoking, baseline BMI, alcohol intake, physical activity, hypertension, high cholesterol, and use of multivitamins. Compared with men who rarely or never consumed breakfast cereals, those who consumed ≥1 serving/d of breakfast cereals were 22% and 12% less likely to become overweight during follow‐up periods of 8 and 13 years (relative risk, 0.78 and 0.88; 95% confidence interval, 0.67 to 0.91 and 0.76 to 1.00, respectively). Discussion: BMI and weight gain were inversely associated with intake of breakfast cereals, independently of other risk factors.     

Prevalence of obesity and correlations with lifestyle and dietary factors in Chinese men

Objective: To estimate the age‐adjusted prevalence of general and centralized obesity among Chinese men living in urban Shanghai. Methods and Procedures: A cross‐sectional study was conducted in 61,582 Chinese men aged 40–75. BMI (kg/m²) was used to measure overweight (23 ≤ BMI < 27.4) and obesity (BMI ≥ 27.5) based on the World Health Organization (WHO) recommended criteria for Asians. Waist‐to‐hip ratio (WHR) was used to measure moderate (75th ≤ WHR < 90th percentile) and severe (WHR ≥ 90th percentile) centralized obesity. Results: The average BMI and WHR were 23.7 kg/m² and 0.90, respectively. The prevalence of overweight was 48.6% and obesity was 10.5%. The prevalence of general and centralized obesity was higher in men with high income or who were retired, tea drinkers, or nonusers of ginseng than their counterparts. Men with high education had a higher prevalence of overweight and centralized obesity, but had a lower prevalence of obesity and severe centralized obesity compared to those with less education. Current smokers or alcohol drinkers had a lower prevalence of general obesity but higher prevalence of centralized obesity than nonsmokers or nondrinkers of alcohol. Ex‐smokers and ex‐alcohol drinkers had a higher prevalence of general and centralized obesity compared to nonsmokers and nondrinkers of alcohol. Prevalence of obesity was associated with high energy intake and less daily physical activity. Discussion: The prevalence of obesity among Chinese men in urban Shanghai was lower than that observed in Western countries but higher than that in other Asian countries, and the prevalence of general and centralized obesity differed by demographic, lifestyle, and dietary factors.     

Long-term effects of obesity on employment and work limitations among U.S. Adults, 1986 to 1999

Objective: To determine the relationships between BMI and workforce participation and the presence of work limitations in a U.S. working‐age population. Research Methods and Procedures: We used data from the Panel Study of Income Dynamics, a nationwide prospective cohort, to estimate the effect of obesity in 1986 on employment and work limitations in 1999. Individuals were classified into the following weight categories: underweight (BMI < 18.5), normal weight (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), and obese (BMI ≥ 30). Using multivariable probit models, we estimated the relationships between obesity and both employment and work disability. All analyses were stratified by sex. Results: After adjusting for baseline sociodemographic characteristics, smoking status, exercise, and self‐reported health, obesity was associated with reduced employment at follow‐up [men: marginal effect (ME) ?4.8 percentage points (pp); p < 0.05; women: ME ?5.8 pp; p < 0.10]. Among employed women, being either overweight or obese was associated with an increase in self‐reported work limitations when compared with normal‐weight individuals (overweight: ME +3.9 pp; p < 0.01; obese: ME +12.6 pp; p < 0.01). Among men, the relationship between obesity and work limitations was not statistically significant. Discussion: Obesity appears to result in future productivity losses through reduced workforce participation and increased work limitations. These findings have important implications in the U.S., which is currently experiencing a rise in the prevalence of obesity.     

Varying patterns of BMI increase in sex and birth cohorts of Korean adults

Objective: The Korean population has recently experienced a rapid increase in obesity associated with lifestyle changes arising from economic growth. We examined trends in BMI by analyzing sex‐specific birth cohorts using 3,400,727 measurements from 1,662,477 Korean adults. Research Methods and Procedures: Birth cohort data were collected from the employees of government organizations and schools and their dependents, 20 to 65 years of age, who participated in health examinations provided by the Korean National Health Insurance Corporation in 1992, 1996, and 2000. Results: The prevalence of obesity (BMI ≥ 30 kg/m²) was 0.8% among men and 0.3% among women in 1992, but by 2000, it had increased 2.5‐fold to 2.0% in men and 2.3‐fold to 0.7% in women. Over the 8‐year period, the mean BMI increased 0.8 kg/m² in men and 0.3 kg/m² in women. The rate of BMI increase over the 8 years varied markedly among the sex‐specific birth cohorts, with the steepest slopes representing the youngest men (0.2 kg/m² per year). Discussion: National health promotion activities should target younger men to prevent an increase in obesity‐related morbidity and mortality.     

The Changing Body Mass–Mortality Association in the United States: Evidence of Sex-Specific Cohort Trends from Three National Health and Nutrition Examination Surveys

The association between body mass index (BMI) categories and mortality remains uncertain. Using three National Health and Nutrition Examination Surveys covering the 1971–2006 period for cohorts born between 1896 and 1968, this study estimates separately for men and women models for year-of-birth (cohort) and year-of-observation (period) trends in how age-specific mortality rates differ across BMI categories. Among women, relative to the normal weight (BMI 18.5–24.9 kg/m²), there are increasing trends in mortality rates for the overweight (BMI 25–29.9) or obese (BMI ≥ 30). Among men, mortality rates relative to the normal weight decrease for the overweight, do not change for the moderately obese (BMI 30–34.9), and increase for the severely obese (BMI ≥ 35). Period and cohort trends are similar, but the cohort trends are more consistent. In the latest cohorts, compared with the normal weight, mortality rates are 50 percent lower for overweight men, not different for moderately obese men, and 100–200 percent higher for severely obese men and for overweight or obese women. For U.S. cohorts born after the 1920s, a lower overweight than normal weight mortality is confined to men. I speculate on possible reasons why the mortality association with overweight and obesity varies by sex and cohort.     

Associations of Maternal Prenatal Smoking with Child Adiposity and Blood Pressure

Objective: To examine the extent to which maternal prenatal smoking is associated with adiposity, central adiposity, and blood pressure in 3‐year‐old children. Research Methods and Procedures: We studied 746 mother‐child pairs in Project Viva, a prospective cohort study, and categorized mothers as never, early pregnancy, or former smokers. Main outcome measures were overweight (BMI for age and sex > 85th percentile), BMI z‐score, sum of subscapular (SS) and triceps (TR) skinfolds, SS:TR skinfold ratio, and systolic blood pressure (SBP). Results: One hundred sixty‐one (22%) mothers quit smoking before pregnancy, 71 (10%) smoked in early pregnancy, and 514 (69%) never smoked. At age 3 years, 204 (27%) children were overweight. On multivariable analysis, compared with children of never smokers, children of early pregnancy smokers had an elevated risk for overweight [odds ratio (OR), 2.2; 95% confidence interval (CI), 1.2, 3.9] and higher BMI z‐score (0.30 units; 95% CI, 0.05, 0.55), SS + TR (2.0 mm; 95% CI, 0.9, 3.0), and SBP (2.4 mm Hg; 95% CI, ?0.1, 4.9). Children of former smokers were not more overweight (BMI z‐score, 0.02 units; 95% CI, ?0.15, 0.19) but had higher SBP (1.5 mm Hg; 95% CI, ?0.1, 3.2). We saw no relationship of smoking with central adiposity (SS:TR). Discussion: Former and early pregnancy smokers had children with somewhat higher SBP, but only early pregnancy smokers had children who were more overweight. Mechanisms linking smoking with child adiposity and blood pressure may differ. A long‐term impact of maternal smoking on offspring cardiovascular risk provides further reason to reduce smoking in women.     

BMI and Mortality: Results From a National Longitudinal Study of Canadian Adults

Although a clear risk of mortality is associated with obesity, the risk of mortality associated with overweight is equivocal. The objective of this study is to estimate the relationship between BMI and all‐cause mortality in a nationally representative sample of Canadian adults. A sample of 11,326 respondents aged ≥25 in the 1994/1995 National Population Health Survey (Canada) was studied using Cox proportional hazards models. A significant increased risk of mortality over the 12 years of follow‐up was observed for underweight (BMI <18.5; relative risk (RR) = 1.73, P < 0.001) and obesity class II+ (BMI >35; RR = 1.36, P <0.05). Overweight (BMI 25 to <30) was associated with a significantly decreased risk of death (RR = 0.83, P < 0.05). The RR was close to one for obesity class I (BMI 30–35; RR = 0.95, P >0.05). Our results are similar to those from other recent studies, confirming that underweight and obesity class II+ are clear risk factors for mortality, and showing that when compared to the acceptable BMI category, overweight appears to be protective against mortality. Obesity class I was not associated with an increased risk of mortality.     

The Role of Overweight and Obesity in Calcium Oxalate Stone Formation

Objective: The aim of the study was to assess the influence of overweight and obesity on the risk of calcium oxalate stone formation. Research Methods and Procedures: BMI, 24‐hour urine, and serum parameters were evaluated in idiopathic calcium oxalate stone formers (363 men and 164 women) without medical or dietetic pretreatment. Results: Overweight and obesity were present in 59.2% of the men and in 43.9% of the women in the study population. Multiple linear regression analysis revealed a significant positive relationship between BMI and urinary uric acid, sodium, ammonium, and phosphate excretion and an inverse correlation between BMI and urinary pH in both men and women, whereas BMI was associated with urinary oxalate excretion only among women and with urinary calcium excretion only among men. Serum uric acid and creatinine concentrations were correlated with BMI in both genders. Because no association was established between BMI and urinary volume, magnesium, and citrate excretion, inhibitors of calcium oxalate stone formation, the risk of stone formation increased significantly with increasing BMI among both men and women with urolithiasis (p = 0.015). The risk of calcium oxalate stone formation, median number of stone episodes, and frequency of diet‐related diseases were highest in overweight and obese men. Discussion: Overweight and obesity are strongly associated with an elevated risk of stone formation in both genders due to an increased urinary excretion of promoters but not inhibitors of calcium oxalate stone formation. Overweight and obese men are more prone to stone formation than overweight women.     

Vitamin E supplementation and plasma 8-isoprostane and adiponectin in overweight subjects

Objective: Isoprostanes are a marker of oxidant stress and atherosclerotic risk, and plasma concentrations are elevated in obesity. Adiponectin is a regulator of insulin sensitivity, and low circulating levels are associated with oxidant stress and obesity. The aim of this study was to determine the effect of vitamin E supplementation on plasma concentrations of 8‐isoprostane and adiponectin in overweight/obese subjects. Research Methods and Procedures: The study was a 6‐month, randomized, double‐blind, placebo‐controlled trial in 80 overweight subjects (60 women and 20 men, BMI >27 kg/m²). Exclusion criteria were serious illness, smoking, or taking antioxidant supplements. Participants were randomized to receive 800 IU/d natural vitamin E (n = 39) or placebo (n = 41) for 3 months with an increase in the dose to 1200 IU/d for a further 3 months. Plasma 8‐isoprostane and adiponectin concentrations were measured at baseline and 3 and 6 months. Results: During 6 months of supplementation with vitamin E, plasma vitamin E concentration increased significantly (p < 0.001) by 76%, and plasma 8‐isoprostane concentrations decreased significantly (?11%, p = 0.03), whereas plasma adiponectin concentrations did not change significantly. Discussion: These findings suggest that supplementation with high‐dose vitamin E decreases systemic oxidative stress and 8‐isoprostane concentrations in overweight/obese individuals. A decrease in plasma 8‐isoprostane has the potential to reduce risk of cardiovascular disease in obesity.     

Overweight and Obesity in Young and Middle Age and Early Retirement: The ARIC Study

The objective of this study was to examine associations between weight status in young and middle age and early retirement in African‐American and white men and women. Data were from the Atherosclerosis Risk in Communities (ARIC) study. Analyses were restricted to participants aged 45–55 years at baseline (n = 6,483). Associations between weight status at age 25 and ages 45–55 and age at early retirement (prior to age 65) over 9 years of follow‐up were examined using proportional hazard regression analyses in models stratified by race and gender. Models were adjusted for education, household income, health insurance status, occupation, occupational physical activity, marital status, smoking, and field center. Between 18.7 and 21.6% of African‐American and white men and women reported retiring prior to age 65. Although not always statistically significant, overweight and obesity were associated with early retirement in all but white women. Overweight (BMI ≥ 25 kg/m²) at age 25 was significantly associated with early retirement in African‐American women (hazard ratio (95% confidence interval): 1.62 (1.17–2.23)) and white men (1.32 (1.12–1.57)). There was also a trend between overweight at age 25 and early retirement in African‐American men (1.43 (0.99–2.07)). Obesity (BMI ≥ 30 kg/m²) in middle age was significantly associated with early retirement in white men only (1.32 (1.03–1.69)). Furthermore, overweight at age 25 and obesity at ages 45–55 were associated with early retirement for health reasons among African‐American and white men and women. In conclusion, analyses of the economic impact of obesity may need to consider its effects on early retirement.