Optimum BMI?

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Optimum BMI?

Postby DianeR » Sat May 17, 2008 6:15 am

I was curious what you have run across in terms of the health and longevity effects of different points in the officially healthy BMI range of 18.5 to 24.9. I think in another thread you said it was best to be at the bottom of this range. Is lower always better or is the optimum somewhere else?

Or is body fat percentage a better measure? And if so, what is the optimum there?

I've tried to research this myself in the past. But it seems what I could find didn't adjust for people who had low weight because of illness or insufficient available calories.
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Re: Optimum BMI?

Postby JeffN » Sat May 17, 2008 10:07 am

DianeR wrote:I was curious what you have run across in terms of the health and longevity effects of different points in the officially healthy BMI range of 18.5 to 24.9. I think in another thread you said it was best to be at the bottom of this range. Is lower always better or is the optimum somewhere else?

Or is body fat percentage a better measure? And if so, what is the optimum there?

I've tried to research this myself in the past. But it seems what I could find didn't adjust for people who had low weight because of illness or insufficient available calories.


Hi Diane,

There is no one simple answer as there are many things that influence mortality & influence BMI. And BMI is only one factor that may influence mortality.

As you mentined, some of the studies show conflicting info 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 exapmles of issues that can all contribute to lowered mortality & lower BMI.

However, when studies have tried to factor out these other issues, we see lower disease rates and a lower mortality at BMIs in the 18.5 to 23 range, depending on the study & how they grouped the subjects.

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Postby JeffN » Sat May 17, 2008 3:26 pm

"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.


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Postby DianeR » Sun May 18, 2008 7:32 am

Thanks! It is always nice to have ammunition when people tell me I'm too skinny. I'm hovering around a 19 BMI now.

Did that study happen to look at osteoporosis? My sister keeps claiming that my light frame (I'm really short too) is a big risk factor for osteoporosis, which our mom has. Of course, I tell her that the real risk factors are things like animal protein, high sodium, and a lack of significant weight-bearing exercise. And of course, she doesn't listen to me or look at my links because I'm the little sister ...

My mother-in-law also tells my husband that I'm too skinny and need to gain some weight.

Need I mention that both big sis and MIL are not in the healthy weight range?

Is there any evidence of any difference in the 18.5 and 21.9 range?

Maybe now that you've answered, I can tell my relatives that I've consulted a famous nutritionist and my weight is just fine :lol:
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Postby JeffN » Sun May 18, 2008 12:45 pm

DianeR wrote:Did that study happen to look at osteoporosis? My sister keeps claiming that my light frame (I'm really short too) is a big risk factor for osteoporosis, which our mom has. Of course, I tell her that the real risk factors are things like animal protein, high sodium, and a lack of significant weight-bearing exercise.


No. But, low BMI's are associated with an increased risk but I do not know that to be true for BMI's within the healthy range. Also, there are some serious issues with the DEXA and how accurate the readings are, especially for people who are smaller and/or thinner, especially thinner.

All the other issues are important also.

DianeR wrote:Is there any evidence of any difference in the 18.5 and 21.9 range?


Not, that I know of. I have a few other citations, that are eluding me right now, but show the same thing as the one above, a lower risk of DB, HTN and increased longevity at the 18.5-22 range.

But again, remember, BMI is just one marker.

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Postby Melinda » Sun May 18, 2008 9:21 pm

Jeff, I have been wondering re the BMI's - it doesn't really allow for differences in body frame. For example, there can be quite a difference in the frame and muscle structure of a woman who is 5'8" and a man who is 5'8''. So I don't trust BMI. My BMI is low, but my husband who is a medium build and slim has a much higher BMI. What do you think?
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Other Markers

Postby Dangling Carrots » Mon May 19, 2008 10:09 am

What are the other markers to consider other than BMI? I'm guessing cholesterol and glucose levels but are there others?

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Postby JeffN » Mon May 19, 2008 11:45 am

There are many biomarkers used to help determine/evaluate someones health.

These include (but not limited to)

BMI,
Waist Circumference
Waist to hip ratio
Waist to height ratio
Percentage Body Fat

Total Cholesterol
LDL
HDL
LDL/HDL
Total Cholesterol/HDL
Triglycerides

Blood sugar
insulin

Etc, etc

BMI is just one marker, as are all of the rest, and no one marker alone can predict someones health outcomes. And, they are just markers.

Or as the old saying goes, they are "fingers pointing to the moon" but not the "moon" itself.

I still think the "plate test" is the best test there is :)

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Postby JeffN » Sat May 31, 2008 5:44 am

FYI,

Excerpts from....

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

Three studies of human subjects living in wealthy countries suggest that low levels of consumption can have beneficial effects on health. Two of the studies, the Okinawa study (Kagawa, 1978) and the Nurses' Health study (Manson et al., 1995), were correlational studies demonstrating that health and longevity are greatest in individuals whose levels of consumption and body weights, respectively, are below prescribed national norms. The third study, the Biosphere 2 study (Walford, Harris, & Gunion, 1992), was an uncontrolled experimental demonstration that an improvement in health can result from a substantial reduction of food intake in ostensibly normal-weight, healthy individuals.

In the Okinawa study (Kagawa, 1978), the caloric intake and health of inhabitants of the Japanese island of Okinawa were compared with those of inhabitants of other parts of Japan. Adult Okinawans were found to consume, on average, 20% fewer calories than other adult Japanese, and Okinawan school children were found to consume 38% fewer calories than recommended by Japanese health authorities. Remarkably, the rates of morbidity and mortality in Okinawa were found to be markedly lower than in other parts of Japan, a country in which overall levels of caloric intake and obesity are well below Western norms (see Kagawa, 1978). Most notably, the death rates from stroke, cancer, and heart disease in Okinawa were only 59%, 69%, and 59%, respectively, of those in the rest of Japan, and the death rate for Okinawans between 60 and 64 years of age was only 50% of the Japanese average. Indeed, the proportion of Okinawans living to be over 100 years of age was 5 to 40 times greater than that of inhabitants of various other areas of Japan.

In the Nurses' Health study (Manson et al., 1995), the association between body-mass index and mortality was assessed in a large cohort of U.S. female nurses-levels of consumption were not directly measured. In this study, over 100,000 female nurses were recruited and studied over a 16-year period. In contrast to previous studies of the relation between body-mass index and mortality (see, e.g., Stevens et al., 1992; Tuomilehto et al., 1987; Wilcosky, Hyde, Anderson, Bangdiwala, & Duncan, 1990), this study controlled the confounding effects of cigarette smoking, which is more prevalent among relatively lean people (Garrison, Feinleib, Castelli, & McNamara, 1983). In addition, it controlled the effects of several other potential confounds, including age, levels of alcohol consumption, levels of dietary fat intake, menopausal status, preexisting disease, illness-related weight loss, and levels of physical activity. 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.

In the Biosphere 2 study (Walford et al., 1992), four normal-weight females, three normal-weight males, and one mildly overweight male lived continuously for two years in a self-contained ecosystem: the so-called Biosphere 2. During their first six months in Biosphere 2, the eight participants were limited to a diet of 1,780 calories per day, an intake nearly 600 calories less than the current North American average (Walford & Walford, 1994). Among the health benefits observed in participants following this six-month period were decreases of 15% in average body weight, 30%/27% in average blood pressure, 38% in average cholesterol level, 20% in average fasting blood glucose level, and 24% in average white blood cell count.

The results of the aforementioned studies have been the focus of attention (e.g., Weindruch, 1996) because of their provocative implication that consumption below levels prevalent in wealthy countries can improve health and longevity. However, because they were uncontrolled, these three studies, even when considered together, provide only equivocal support for this conclusion. For example, it is impossible to rule out the possibility that the effects on health in each of the three studies were mediated by differences in the constitution of the high-calorie and low-calorie diets, rather than by total caloric intake per se; because the constituents of the high-calorie and low-calorie diets were not equated in any of the three studies, the health gains may have resulted from the fact that the lower calorie diets were richer in health-promoting nutrients and lower in toxins and fats than the high-calorie diets. However, this and other methodological problems (e.g., self-selection) have been resolved by controlled experiments on dietary restriction in nonhuman species.
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Postby DianeR » Sat May 31, 2008 8:10 am

What studies support the idea that a BMI less than 18.5 is unhealthy, if you know? I tried looking for them once (when I was below 18.5 :lol: ) and couldn't find anything very good. What I was finding were studies of other countries where a low BMI was probably due to not having enough to eat or illness.

Now I'm right at 19. I seemed to have gained muscle when I upped the weight training a year ago.

You have me wondering if I should try to lose a little. I know, I'm too much a perfectionist :D

Maybe a better marker than BMI is body fat percentage. Is there any good research on that? I've seen widely divergent recommendations. Some would say I don't have enough body fat and others say the optimum is a little less than what I have.
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Postby JeffN » Sat May 31, 2008 9:11 am

There is no one marker so do not obsess over this. I was just providing more information about the question you asked showing why being in the lower range of normal "may" be better. These studies do not in anyway prove a single number is the best.

Also, there are some studies that have accounted for smoking, illness and disease and have showed a J curve for BMI meaning there is a point where you can go to low and I beleive it was shown around a BMI of 18 for men. I do not remember off hand what it was for women

Relax!

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Postby JeffN » Sun Jul 13, 2008 4:23 pm

Some more info on the topic...

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1) A large, 5 year study found:

“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.” [1]

2) Available well-researched and well-analyzed epidemiology shows that mortality (among nonsmokers without preexisting medical conditions) is lowest in people with the lowest BMI. [2]

3) From a 1987 careful literature methods review in JAMA, “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 was 10% below the 1987 average, which was
significantly below the current average BMI] [3]


[1] 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


[2] Lee IM, Manson JE, Hennekens CH, Paffenbarger RS Jr. Body weight and mortality. A 27-year follow-up of middle-aged men. JAMA. 1993 Dec 15;270(23):2823-8. PMID: 8133621

[3] Manson JE, Stampfer MJ, Hennekens CH, Willett WC. Body weight and longevity. A reassessment. JAMA. 1987 Jan 16;257(3):353-8. PMID: 3795418
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Postby JeffN » Thu Jul 24, 2008 6:27 am

I found two more..

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.”


And 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.”

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17.5 bmi = 122 lbs for me at 5'10"

Postby MarkCSpangenberg » Thu Jul 24, 2008 6:50 am

Would need to lose 148lbs. Even when I ran cross country/track in high school and would do one run a week of 15-18 miles, my weight would range from 125 to 135 (on daily basis - weight would fluctuate 10lbs).
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Re: 17.5 bmi = 122 lbs for me at 5'10"

Postby JeffN » Thu Jul 24, 2008 7:04 am

MarkCSpangenberg wrote:Would need to lose 148lbs. Even when I ran cross country/track in high school and would do one run a week of 15-18 miles, my weight would range from 125 to 135 (on daily basis - weight would fluctuate 10lbs).


Hi Mark

Thanks and good point.

This information and these numbers are posted in light of the original question and are in no way posted here as the ideal recommendations and goal for everyone.

Studies have also clearly shown that regardless of what your current weight and/or BMI is, just losing 5-10% of your weight will produce significant health benefits. And, regardless of what your current weight and/or BMI is, exercising and being physically fit will lower your risks.

Some people are just to short for their weight. :)

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