Body weight and mortality

Just because people have a low BMI does not mean they are on Calorie Restriction or have the optimal nutrition part. Controlling for all factors that result in a low body weight would be difficult. Usually they just exclude deaths in the first 5 years and see if it attenuates the increase in death among underweight and overweight people. Sometimes this actually works, but sometimes it doesn't and for those reasons it seems that something is being missed and that trying to figure out this mess will be difficult because the results are fairly inconsistent. I argue that the mere fact that some cohorts have actually shown a decrease in mortality and morbidity when at a low BMI then it gives us hope that [UNDER CERTAIN CIRCUMNSTANCES] like CRON, we will have a more favourable response. Below are just a few studies that I have collected to show that low BMI doesn't always = higher mortality. The studies I've chosen here were for obvious reasons. Seventh day adventsts and Physicians for example would be more health conscious and therefor avoid some factors that could influence mortality.

Body mass index and mortality among US male physicians.
Ann Epidemiol. 2004 Nov;14(10):731-9.
PURPOSE: To assess the relationship between body mass index and mortality in a population homogeneous in educational attainment and socioeconomic status. METHODS: We analyzed the association between body mass index (BMI) and both all-cause and cause-specific mortality among 85,078 men aged 40 to 84 years from the Physicians' Health Study enrollment cohort. RESULTS: During 5 years of follow-up, we documented 2856 deaths (including 1212 due to cardiovascular diseases and 891 due to cancer). In age-adjusted analyses, we observed a U-shaped relation between BMI and all-cause mortality; among men who never smoked a linear relation was observed with no increase in mortality among leaner men (P for trend, <0.001). Among never smokers, in multivariate analyses adjusted for age, alcohol intake, and physical activity, the relative risks of all-cause mortality increased in a stepwise fashion with increasing BMI. Excluding the first 2 years of follow-up further strengthened the association (multivariate relative risks, from BMI<20 to > or = 30 kg/m2, were 0.93, 1.00, 1.00, 1.16, 1.45, and 1.71 [P for trend, <0.001]). In all age strata (40-54, 55-69, and 70-84 years), never smokers with BMIs of 30 or greater had approximately a 70% increased risk of death compared with the referent group (BMI 22.5-24.9). Higher levels of BMI were also strongly related to increased risk of cardiovascular mortality, regardless of physical activity level (P for trend, <0.01). CONCLUSIONS: All-cause and cardiovascular mortality was directly related to BMI among middle-aged and elderly men. Advancing age did not attenuate the increased risk of death associated with obesity. Lean men (BMI<20) did not have excess mortality, regardless of age.PMID: 15519894 [PubMed - indexed for MEDLINE]

Body mass index and patterns of mortality among Seventh-day Adventist men.Int J Obes. 1991 Jun;15(6):397-406.
This study examines the relationship between body mass index (BMI) and 26-year mortality among 8828 nonsmoking, nondrinking Seventh-day Adventist men, including 439 who were very lean (BMI less than 20 kg/m2). The adjusted relative risk comparing the lowest BMI quintile (less than 22.3) to the highest (greater than 27.5 kg/m2) was 0.70 (95 percent CI 0.63-0.78) for all cause mortality, 0.60 (95 percent CI 0.43-0.85) for cerebrovascular mortality, and 0.80 (95 percent CI 0.61-1.04) for cancer mortality. Very lean men did not show increased mortality. To assess whether the protective effect associated with low BMI is modified by increasing age, the product term between BMI and attained age (age at the end of follow-up or at death) was included as a time-dependent covariate. For ischemic heart disease mortality, age-specific estimates of the relative risk for the lowest quintile relative to the highest ranged from 0.32 (95 percent CI, 0.19-0.52) at age 50 to 0.71 (95 percent CI, 0.56-0.89) at age 90. Interaction was also seen for the next lowest quintile (22.4-24.2). There was a significant trend of increasing mortality with increasing BMI for all endpoints studied. For cancer and cerebrovascular mortality the P-values for trend were 0.0001 and 0.001 respectively. For the other endpoints the P-values were less than 0.0001. Thus, there was no evidence for a J-shaped relationship between BMI and mortality in males. While the protective effect associated with the lowest BMI quintile decreased with increasing age for ischemic heart disease mortality, it remained greater than one at all ages. The relatively large number of subjects who were lean by choice, rather than as a result of preclinical disease or smoking, may explain these findings.PMID: 1885263 [PubMed - indexed for MEDLINE]


Relationship between morbidity and body mass index of mariners in the Japan Maritime Self-Defense Force fleet escort Force
To establish a practical weight management program for mariners in the Japan Maritime Self-Defense Force (JMSDF) Fleet Escort Force, the relationship between morbidity and body mass index (BMI) was studied. To estimate morbidity, 10 medical problems were used as indices (hyperlipidemia, hyperuricemia, diabetes mellitus, lung disease, heart disease, upper gastrointestinal tract disease, hypertension, renal disease, liver disease, and anemia). A curvilinear relationship was found between morbidity and BMI, in which a BMI of 17.5 was associated with the lowest morbidity. This curvilinear pattern was more complex than a curve reported previously for Japanese civilians. Using the present curve and aiming for a BMI of 17.5 will help in the design and implementation of a practical management program for health promotion in the JMSDF.
http://cat.inist.fr/?aModele=afficheN&cpsidt=1101215

NIHNC, CDC, & DHHS. (1985). Body weight, health and longevity: conclusions and recommendations of the workshop. Nutrition Reviews, February, 43(2), pages 61-3.
In 1985, the National Institute of Health, Centers for Disease Control, and the Department of Health and Human Services published a "special report" stating: "[S]tudies based on life insurance data, the American Cancer Society Study and other long-term studies, such as the Framingham Heart Study and the Manitoba Study, indicate that the weights associated with the greatest longevity tend to be below the average weights of the population as long as such weights are not associated with concurrent illness or a history of medical impairment.


Lee IM. et al. (1993). Body weight and mortality. A 27-year follow-up of middle-aged men. Journal of the American Medical Association, December 15, 270(23), pages 2823-8.
In 1993, the Journal of the American Medical Association published a study that concluded: "In these prospective data, body weight and mortality were directly related. After accounting for confounding by cigarette smoking and bias resulting from illness-related weight loss or inappropriate control for the biologic effects of obesity, we found no evidence of excess mortality among lean men. Indeed, lowest mortality was observed among men weighing, on average, 20% below the US average for men of comparable age and height.

Manson E. et al. (1995). Body wight and mortality among women. New England Journal of Medicine, September 14, 333(11), pages 677-85.
In 1995, a study published in New England Journal of Medicine concluded: "Among women who never smoked, the leanest women ... had the lowest mortality, and even women with average weights had higher mortality. Mortality was lowest among women whose weights were below the range of recommended weights in the current U.S. guidelines. Moreover, a weight gain of 10 kg of more since the age of 18 was associated with increased mortality in middle adulthood. These data indicate that the lowest mortality rate for U.S. middle- aged women is found at body weights at least 15 percent below the U.S. average for women of similar age.

Solomon CG. (1997). Obesity and mortality: a review of the epidemiologic data. American Journal of Clinical Nutrition, October, 66(4 Suppl), pages 1044S-1050S.
In 1997, the American Journal of Clinical Nutrition published a study on body weight and mortality stating: "We conclude that when appropriate adjustments are made for effects of smoking and underlying disease, optimal weights [for longevity] are below average in both men and women; this appears to be true throughout the adult life span.