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From: Jeff Novick, MS, RD, LD, LN (novick.vegsource.com)
Subject:         Re: accuracy of bmi tables
Date: July 23, 2008 at 2:20 pm PST

In Reply to: Re: accuracy of bmi tables posted by bmi19.4 on July 23, 2008 at 11:04 am:

Some of the studies have shown conflicting results in regard to whether a lower BMI is healthier in regard to BMI and longevity because they do not always account for some of the medical/health issues that may be contributing to a low BMI. Cancer, smoking, alcoholism, are all examples of issues that can all contribute to a lowered mortality & lower BMI.

1) The following is from a 1987 careful review of the literature methods in JAMA.

Manson JE, Stampfer MJ, Hennekens CH, Willett WC. Body weight and longevity. A reassessment. JAMA. 1987 Jan 16;257(3):353-8. PMID: 3795418

“Conflicting results have been reported concerning the association between body weight and longevity. The shape of the curve relating weight to all-cause mortality has been variously described as linear, J-shaped, and even U-shaped. To assess the validity of the evidence for optimal weight recommendations, we examined the 25 major prospective studies on the subject. Each study had at least one of three major biases: failure to control for cigarette smoking, inappropriate control of biologic effects of obesity, such as hypertension and hyperglycemia, and failure to control for weight loss due to subclinical disease. The presence of these biases leads to a systematic underestimate of the impact of obesity on premature mortality. Although these biases preclude a valid assessment of optimal weight from existing data, available evidence suggests that minimum mortality occurs at relative weights at least 10% below the US average.”

[NOTE: This statement "10% below the US average" was made in 1987, when the average BMI was lower than the current average BMI.]

2) When studies have tried to factor out these other issues, we see lower disease rates and a lower mortality rate at BMIs in the 18.5 to 22 range, depending on the study & how they grouped the subjects In the following study, we see that a BMI between 18.5 and 22 may be best for lowering the risk of disease.

"Impact of Overweight on the Risk of Developing Common Chronic Diseases During a 10-Year Period Arch Intern Med. 2001;161:1581-1586

Conclusions: During 10 years of follow-up, the incidence of diabetes, gallstones, hypertension, heart disease, colon cancer, and stroke (men only) increased with degree of overweight in both men and women. Adults who were overweight but not obese (ie, BMI 25.0 to BMI 29.9) were at significantly increased risk of developing numerous health conditions. Moreover, the dose-response relationship between BMI and the risk of developing chronic diseases was evident even among adults in the upper half of the healthy weight range (ie, BMI of 22.0-24.9), suggesting that adults should try to maintain a BMI between 18.5 and 21.9 to minimize their risk of disease.

The above recommendations are especially important as they come from a ten-year follow-up (1986-1996) of middle-aged women in the Nurses' Health Study and men in the Health Professionals Follow-up Study, two very large and respected epidemiological studies.

3) This large 5 year study found similar results:

Ajani UA, Lotufo PA, Gaziano JM, Lee IM, Spelsberg A, Buring JE, Willett WC, Manson JE. Body mass index and mortality among US male physicians. Ann Epidemiol. 2004 Nov;14(10):731-739. PMID: 15519894

“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. … 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… 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.”

4) We also see similar recommendations from the following study...

Pinel JP, Assanand S, Lehman DR. Hunger, eating, and ill health. Am Psychol. 2000 Oct;55(10):1105-16. PMID: 11080830

"Most notably, the results revealed a positive correlation between body-mass index and mortality, with the lowest mortality rate occurring among those nurses with body-mass indices below 19-that is, among those nurses weighing at least 15% below the average weight of U.S. women of a similar age and at least 10% below their recommended weights according to the widely used Metropolitan Life Insurance Company Table of 1983. Furthermore, negative correlations were observed between body-mass index and various measures of health: Diabetes, gall stones, hypertension, and nonfatal myocardial infarction were all less frequent in the leanest nurses than in the normal-weight or overweight nurses. Apparently, the various health advantages of a low body-mass index had not been detected in previous studies (e.g., Tuomilehto et al., 1987) because they had not controlled for cigarette smoking."

5) This twenty year prospective study found the lowest mortality in the BMIs < 20...

Greenberg JA. Biases in the mortality risk versus body mass index relationship in the NHANES-1 Epidemiologic Follow-Up Study. Int J Obes Relat Metab Disord. 2001 Jul;25(7):1071-8. PMID: 11443509

“Average-adulthood BMI appears to be an appropriate predictor of mortality risk, provided baseline BMI is used as a covariate. Among non-elderly persons, being leaner meant a lower mortality risk, down to the lowest category of leanness in the study: [BMI < 20].”


6) This study on the 115,195 U.S. women enrolled in the prospective Nurses' Health Study found the lowest mortality rate among women who weighed at least 15 percent less than the U.S. average

Manson JE, Willett WC, Stampfer MJ, Colditz GA, Hunter DJ, Hankinson SE, Hennekens CH, Speizer FE. Body weight and mortality among women. N Engl J Med.
1995 Sep 14;333(11):677-85. PMID: 7637744

“A weight gain of 10 kg (22 lb) or more since the age of 18 was associated with increased mortality in middle adulthood. CONCLUSIONS. Body weight and mortality from all causes were directly related among these middle-aged women. Lean women did not have excess mortality. The lowest mortality rate was observed among women who weighed at least 15 percent less than the U.S. average for women of similar age and among those whose weight had been stable
since early adulthood.”


7) And finally, this one found the lowest morbidity at a BMI of 17.5

Relationship between morbidity and body mass index of mariners in the Japan Maritime Self-Defense Force Fleet Escort Force. Mil Med. 2001 Aug;166(8):681-4. PMID: 11515316

“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…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.”

Sometimes, "less is more"

Regards
Jeff

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