To continue where we left off in our discussion of body weight, disease risk and longevity...
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.
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.”
We also see similar recommendatons 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."
A twenty year prospective study found that “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].”
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
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
So, as you can see, there is lots of good evidence to maintain a healthy BMI (18.5-25) in regard to both lowering your disease risk and in potentially increasing your lifespan. And, in addition, maintaining a BMI in the lower range of the "healthy" category (18.5-22) or slightly lower, may be the best.
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.”
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.”
This may just be one of those times, where "less is more!"