Mortality in Micronesian Nauruans and Melanesian and Indian Fijians is not associated with obesity

Do the Low WHRs and BMIs Judged Most Attractive Indicate Better Health?

It is widely claimed that in well-nourished populations, very low female waist-hip ratios (WHRs) together with low body mass indices (BMIs) are judged attractive by men because these features reliably indicate superior health and fertility. However, studies show that mortality rates are higher in women with low BMIs than in women with average BMIs and are inversely related to BMI in subsistence populations. Measures of current health in women of reproductive age have not been similarly studied. We analyze large U.S. samples of reproductive-age women and show that controlling for other factors known to affect health, those with low BMIs (<20), WHRs, or waist/stature ratios did not have better health than those with values in the middle range, and there was no relationship between subsequent health outcomes and BMI in early adulthood. Lower self-reported BMIs were linked to poorer health and an increased risk of infection. However, based on recent U.S. natality data, primiparas with lower BMIs had a lower risk of an operative delivery and of gestational hypertension. Beyond these two parity-restricted effects, relevant studies and new tests fail to support the view that women with the very low BMIs and WHRs consistently judged attractive are generally healthier than women with average values; significant correlations were consistently in the opposite direction.

BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants

OBJECTIVE

To conduct a systematic review and meta-analysis of cohort studies of body mass index (BMI) and the risk of all cause mortality, and to clarify the shape and the nadir of the dose-response curve, and the influence on the results of confounding from smoking, weight loss associated with disease, and preclinical disease.

DATA SOURCES

PubMed and Embase databases searched up to 23 September 2015.

STUDY SELECTION

Cohort studies that reported adjusted risk estimates for at least three categories of BMI in relation to all cause mortality.

DATA SYNTHESIS

Summary relative risks were calculated with random effects models. Non-linear associations were explored with fractional polynomial models.

RESULTS

230 cohort studies (207 publications) were included. The analysis of never smokers included 53 cohort studies (44 risk estimates) with >738 144 deaths and >9 976 077 participants. The analysis of all participants included 228 cohort studies (198 risk estimates) with >3 744 722 deaths among 30 233 329 participants. The summary relative risk for a 5 unit increment in BMI was 1.18 (95% confidence interval 1.15 to 1.21; I(2)=95%, n=44) among never smokers, 1.21 (1.18 to 1.25; I(2)=93%, n=25) among healthy never smokers, 1.27 (1.21 to 1.33; I(2)=89%, n=11) among healthy never smokers with exclusion of early follow-up, and 1.05 (1.04 to 1.07; I(2)=97%, n=198) among all participants. There was a J shaped dose-response relation in never smokers (Pnon-linearity <0.001), and the lowest risk was observed at BMI 23-24 in never smokers, 22-23 in healthy never smokers, and 20-22 in studies of never smokers with ≥20 years' follow-up. In contrast there was a U shaped association between BMI and mortality in analyses with a greater potential for bias including all participants, current, former, or ever smokers, and in studies with a short duration of follow-up (<5 years or <10 years), or with moderate study quality scores.

CONCLUSION

Overweight and obesity is associated with increased risk of all cause mortality and the nadir of the curve was observed at BMI 23-24 among never smokers, 22-23 among healthy never smokers, and 20-22 with longer durations of follow-up. The increased risk of mortality observed in underweight people could at least partly be caused by residual confounding from prediagnostic disease. Lack of exclusion of ever smokers, people with prevalent and preclinical disease, and early follow-up could bias the results towards a more U shaped association.

Mortality trends and the epidemiological transition in Nauru

This article aims to examine the epidemiological transition in Nauru through analysis of available mortality data. Mortality data from death certificates and published material were used to construct life tables and calculate age-standardized mortality rates (from 1960) with 95% confidence intervals. Proportional mortality was calculated from 1947. Female life expectancy (LE) varied from 57 to 61 years with no significant trend. Age-standardized mortality for males (15-64 years) doubled from 1960-1970 to 1976-1981 and then decreased to 1986-1992, with LE fluctuating since then from 49 to 54 years. Proportional mortality from cardiovascular disease and diabetes increased substantially, reaching more than 30%. Nauru demonstrates a very long period of stagnation in life expectancy in both males and females as a consequence of the epidemiological transition, with major chronic disease mortality in adults showing no sustained downward trends over 40 years. Potential overinterpretation of trends from previous data due to lack of confidence intervals was highlighted.

Obesity paradox and cardiorespiratory fitness in 12,417 male veterans aged 40 to 70 years

OBJECTIVE

To evaluate the influence of cardiorespiratory fitness (fitness) on the obesity paradox in middle-aged men with known or suspected coronary artery disease.

PATIENTS AND METHODS

This study consists of 12,417 men aged 40 to 70 years (44% African American) who were referred for exercise testing at the Veterans Affairs Medical Centers in Washington, DC, or Palo Alto, CA (between January 1, 1983, and June 30, 2007). Fitness was quantified as metabolic equivalents achieved during a maximal exercise test and was categorized for analysis as low, moderate, and high (defined as <5, 5-10, and >10 metabolic equivalents, respectively). Adiposity was defined by body mass index (BMI) according to standard clinical guidelines. Separate and combined associations of fitness and adiposity with all-cause mortality were assessed by Cox proportional hazards analyses.

RESULTS

We recorded 2801 deaths during a mean+/-SD follow-up of 7.7+/-5.3 years. Multivariate hazard ratios (95% confidence interval) for all-cause mortality, with normal weight (BMI, 18.5-24.9 kg/m2) used as the reference group, were 1.9 (1.5-2.3), 0.7 (0.7-0.8), 0.7 (0.6-0.7), and 1.0 (0.8-1.1) for BMIs of less than 18.5, 25.0 to 29.9, 30.0 to 34.9, and 35.0 or more kg/m2, respectively. Compared with highly fit normal-weight men, underweight men with low fitness had the highest (4.5 [3.1-6.6]) and highly fit overweight men the lowest (0.4 [0.3-0.6]) mortality risk of any subgroup. Overweight and obese men with moderate fitness had mortality rates similar to those of the highly fit normal-weight reference group.

CONCLUSION

Fitness altered the obesity paradox. Overweight and obese men had increased longevity only if they registered high fitness.

Mortality in people with type 2 diabetes in the UK

AIMS

Under-reporting of diabetes on death certificates contributes to the unreliable estimates of mortality as a result of diabetes. The influence of obesity on mortality in Type 2 diabetes is not well documented. We aimed to study mortality from diabetes and the influence of obesity on mortality in Type 2 diabetes in a large cohort selected from the General Practice Research Database (GPRD). Methods A cohort of 44 230 patients aged 35-89 years in 1992 with Type 2 diabetes was identified. A comparison group matched by year of birth and sex with no record of diabetes at any time was identified (219 797). Hazards ratios (HRs) for all-cause mortality during the period January 1992 to October 1999 were calculated using the Cox Proportional Hazards Model. The effects of body mass index (BMI), smoking and duration of diabetes on all-cause mortality amongst people with diabetes was assessed (n = 28 725). Results The HR for all-cause mortality in Type 2 diabetes compared with no diabetes was 1.93 (95% CI 1.89-1.97), in men 1.77 (1.72-1.83) and in women 2.13 (2.06-2.20). The HR decreased with increasing age. In the multivariate analysis in diabetes only, the HR for all-cause mortality amongst smokers was 1.50 (1.41-1.61). Using BMI 20-24 kg/m(2) as the reference range, for those with a BMI 35-54 kg/m(2) the HR was 1.43 (1.28-1.59) and for those with a BMI 15-19 kg/m(2) the HR was 1.38 (1.18-1.61).

CONCLUSIONS

Patients with Type 2 diabetes have almost double the mortality rate compared with those without. The relative risk decreases with age. In people with Type 2 diabetes, obesity and smoking both contribute to the risk of all-cause mortality, supporting doctrines to stop smoking and lose weight.

Body mass index and mortality: a meta-analysis based on person-level data from twenty-six observational studies

PURPOSE

For this report, we examined the relationships between the conditions of being overweight and obese and mortality from all causes, heart disease, cardiovascular disease, and cancer.

METHODS

We defined the categories of body weight according to level of body mass index, BMI=wt(kg)/ht(m)2, using classifications suggested by the National Institutes of Health and the World Health Organization. These classifications are as follows: "normal weight" is defined as BMI > or = 18.5, but less than 25; "overweight" equals BMI > or = 25, but less than 30; and "obese" individuals have BMIs > or = 30. Our investigation is based on person-level data from 26 observational studies that include both genders, several racial and ethnic groups, and samples from the US and other countries. The database consists of 74 analytic cohorts, arranged according to natural strata including gender, race, and area of residence. It includes 388,622 individuals, with 60,374 deaths during follow-up. We use proportional hazards models to examine the relationships between the BMI categories and mortality, controlling for age and smoking status. We use random-effects models to assess summary relative risks associated with the overweight and obesity conditions across cohorts.

RESULTS

The relative risks among the heaviest individuals for overall death, death caused by coronary heart disease (CHD), and death caused by cardiovascular disease (CVD) are 1.22, 1.57, and 1.48, respectively, when compared with the those within the lowest BMI category. The summary relative risk among the heaviest participants for death from cancer is 1.07.

CONCLUSIONS

We document once again, excess mortality associated with obesity. Our results do, however, question whether the current classification of individuals as "overweight" is optimal in the sense, since there is little evidence of increased risk of mortality in this group.

Role of a critical visceral adipose tissue threshold (CVATT) in metabolic syndrome: implications for controlling dietary carbohydrates: a review

There are likely many scenarios and pathways that can lead to metabolic syndrome. This paper reviews mechanisms by which the accumulation of visceral adipose tissue (VAT) may contribute to the metabolic syndrome, and explores the paradigm of a critical VAT threshold (CVATT). Exceeding the CVATT may result in a number of metabolic disturbances such as insulin resistance to glucose uptake by cells. Metabolic profiles of patients with visceral obesity may substantially improve after only modest weight loss. This could reflect a significant reduction in the amount of VAT relative to peripheral or subcutaneous fat depots, thereby maintaining VAT below the CVATT. The CVATT may be unique for each individual. This may help explain the phenomena of apparently lean individuals with metabolic syndrome, the so-called metabolically normal weight (MONW), as well as the obese with normal metabolic profiles, i.e., metabolically normal obese (MNO), and those who are "fit and fat." The concept of CVATT may have implications for prevention and treatment of metabolic syndrome, which may include controlling dietary carbohydrates. The identification of the CVATT is admittedly difficult and its anatomical boundaries are not well-defined. Thus, the CVATT will continue to be a work in progress.

Body mass index and mortality in aboriginal Australians in the Northern Territory

OBJECTIVE

To assess the association between body mass index and the risk of all-cause and disease-specific mortalities in Australian Aborigines in a remote community.

DESIGN

A community based cohort study.

PARTICIPANTS AND SETTING

744 Aboriginal adults aged 20 to 77 years in a remote community in Northern Territory. Eighty-seven deaths occurred during the follow-up period of 5,040.8 person-years.

MEASURES

Mortality data for the period of 1992 and June 2000 were collected. Mortality rate ratios for each body mass index quartile was determined using a Cox proportional hazards model with adjustment for age, sex, and smoking and drinking status.

RESULTS

An inverse relationship between BMI quartiles and the risk of all-cause, natural, and non-CVD mortality was found. Adjusted rate ratios (95% CI) of all-cause mortality were 0.92 (0.54-1.59), 0.71 (0.40-1.26) and 0.38 (0.19-0.75) for second, third and fourth BMI quartiles, respectively, with the first quartile as the reference. The fourth BMI quartile had the lowest risk of mortality with adjusted rate ratios of 0.38, 0.28, and 0.16 for deaths from all-cause, natural, and non-CVD, respectively. However, the associations between BMI and CVD and renal deaths did not reach statistical significance.

CONCLUSIONS

BMI and mortality are inversely associated in Aboriginal adults in a remote community. Individuals with relatively higher BMI have a lower risk of death.

Human obesity: an evolutionary approach to understanding our bulging waistline

The unique worldwide spread of the human species and the remarkably long post-reproductive survival show that our genome permits excellent adaptation to vastly different environments. Moreover, the main scourges of later age, namely malignant growths and atherosclerosis, appear in humans later than in shorter-living animals. In recent years, excess weight and obesity have become mass phenomena with a pronounced upward trend in all developed countries. However, despite the detrimental effects of being overweight, these populations live longer than ever, which in part may be explained by the availability of better medical treatment. The prevalence and predicted further spread of obesity can be understood in the light of evolution. In all animal species energy metabolism is asymmetric with energy accumulation ('thrifty genotype') being the necessary condition of survival during hard times. For humans, which are no different to other animals in this respect, this genetic programming was necessary for survival because during the course of history, including the recorded history in the more developed Middle East, Europe or China, there was never a long period of uninterrupted food abundance, whereas famines were regular and frequent. Therefore fat accumulation, when food was available, meant survival at times of shortage, while the possible detrimental effects of overindulgence in food and being overweight expressed in unrealistically old age were irrelevant. It is the central, mostly intra-abdominal fat (in both humans and animals) that is more medically important than the subcutaneous truncal fat, and the accumulation of both types of fat is conditioned by high food consumption; therefore it is a historic novelty for human populations. In contrast, lower-body fat in human females is unique in the animal kingdom: it is much less metabolically active, it is of much lower pathologic significance than central fat, and it is programmed to be mobilized mostly during pregnancy and lactation. In view of all this, norms of desired weight should be based on hard mortality and morbidity statistics and not on theoretical, esthetic or fashion considerations. By this criterion, the upper limit of desirable weight is likely to be body mass index (BMI) 27 or 28, but specified for different populations (sex, race, ethnic origin); moreover, with aging, the detrimental effects of obesity diminish and finally disappear. Risks of other pathologies related to obesity (e.g. diabetes, hypertension and coronary disease) are also population-specific. However, total fatness, measured by BMI, is insufficiently sensitive as a risk factor, and fat distribution (upper-body versus low-body type, as reflected by waist circumference and waist:hip ratio) plays at least as prominent a role. Therefore the detailed norms, not yet available, should take into account both general obesity and fat distribution and be specific for different populations. Since long-term weight loss in adults is rarely achievable, public health measures should be aggressively directed at the prevention of obesity from childhood.

Obesity in North America. An overview

The terms "obesity" and "overweight" mean different things to different people. This article discusses such issues as prevalence, morbidity, mortality, and psychosocial effects. Definitions and various classifications of obesity are discussed also.