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Michael R

Relationship Between BMI and Disease, and Longevity

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I came across an interesting study, discussing, among other things, BMI:

Assessment of the Health Status of Centenarians in the South of China: A Cross‐Sectional Study

"The average age of the centenarians (85.0% female, 15.0% male) was 102. Average height was 146.7 ± 0.5 cm, average weight was 36.0 ± 0.4 kg, and average BMI was 16.7 ± 0.1 kg/m2. Only two of 271 centenarians for whom information was available were overweight, and none were obese. Alanine aminotransferase, total protein, albumin, globin, blood urine nitrogen, creatinine, and uric acid levels were all in normal physiological ranges. Levels of the important risk factors for cardiovascular diseases, blood glucose (101.0 ± 1.6 mg/dL), triglyceride (114.2 ± 3.5 mg/dL), and total cholesterol (180.6 ± 2.3 mg/dL) were significantly lower than those of the general older population (116.1 ± 0.9 mg/dL, 151.4 ± 2.7 mg/dL, and 222.3 ± 1.2 mg/dL, respectively) from the same province.7 These results were in good agreement with results of a previous study.9 Moreover, the prevalence of T2DM (16.9%), HTG (6.5%), and HP (52.9%) was lower in the centenarians than Chinese national levels (25.0%, 12.9%, and 66.9%, respectively). In addition, only four of 349 centenarians for whom information was available had benign tumors (hemangioma or melanoma). It seems that the incidence of age‐related diseases is delayed or reduced in centenarians. This relatively healthy status of centenarians suggests that they can serve as a good model for a healthy aging study. Additional evidence comes from the observation that more than 90% of the centenarians were cognitively normal...."

BMI of 16.1.... And half of them had no teeth. (I wonder how age was verified, but that's a different topic.)

On the subject of low BMI and longevity, here is a grab from search results, as I cannot find the actual text that includes this information:


925209316_ScreenShot2021-04-30at16_26_41.png.3a42bb2e7fd6e72b18175b59b5e1492c.png

BMI is again on the low end for Italiaans and Japanese, while higher for Northern Europeans and Americans. On the other hand, one has to keep in mind the fact that Northern Europeans and Americans have fewer centenarians per capita than the Italians or the Japanese despite generally better access to advanced medical care, and BMI may be a factor.

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From everything I’ve read, including various meta data analysis for the Adventist and China studies, the mortality was directly proportionate to the amount of animal protein consumed.
 

The BMI was also a direct result of the amount of animal protein. Thus, a low BMI but one based on animal protein won’t have a good long term prognosis.

From longest lifespan to lowest 

vegan #1, vegetarian #2, pascaterian #3, Carnivores a dismal 4th.

It will be interesting to see vegetarian studies based upon A2 milk / dairy as opposed to A1 casein.

 

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4 hours ago, Jon Power said:

From everything I’ve read, including various meta data analysis for the Adventist and China studies, the mortality was directly proportionate to the amount of animal protein consumed.

Campbell's China study received a barrage of criticism from unbiased sources as well. Also, a conclusion like that (mortality directly proportionate to animal protein) sounds pretty vegan-biased, that is, originated from studies driven by a specific agenda. I'm reasonably sure that  plant-based protein can increase mortality as well, if consumed in excess. Especially the processed protein like isolated soy, rice hemp and so on. Gastric distress caused by the ingestion of protein-rich plant foods is also a neurological factor which probably does not contribute to longevity.

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Regarding the optimal BMI of 18 in the 1970s and 26 today, there's a shift to higher BMI in the general population. Therefore, today's BMI of 18 is more likely caused by other factors such as mental illness, while in the 1970s it was more likely "naturally occurring" (with smoking excluded in the above study). Coupled with improved healthcare condition, the 26 optimal BMI becomes understandable. I bet that among today's very low BMI population there's a significant prevalence of underlying conditions such as mental illness or illicit substance abuse not reflected in the above cited study that caused their low BMI.

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8 hours ago, Aaron said:

Therefore, today's BMI of 18 is more likely caused by other factors such as mental illness, while in the 1970s it was more likely "naturally occurring" (with smoking excluded in the above study). Coupled with improved healthcare condition, the 26 optimal BMI becomes understandable.

I've had several friends and family members who experienced apparently improved health after giving up smoking despite gaining a few pounds.  I doubt a BMI of 26 is optimal unless one is quite muscular but it appears compatible with a good lifespan if one avoids other egregiously bad things such as smoking, chronic stress, poor sleep, malnutrition, etc.

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10 hours ago, Todd Allen said:

I doubt a BMI of 26 is optimal unless one is quite muscular

I agree. What I meant was today's "optimal 26 BMI" isn't really optimal if the underlying conditions like mental illness were accounted for, which would likely cause the optimal BMI to be closer to 18 of the 1970s.

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14 hours ago, Todd Allen said:

I doubt a BMI of 26 is optimal unless one is quite muscular

A  BMI of 26  with lots of muscle is optimal?    At what  age?   Where's the proof?

Edited by Sibiriak

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9 hours ago, Sibiriak said:

A  BMI of 26  with lots of muscle is optimal?    At what  age?   Where's the proof?

At an age of 122 years and 165 days it is optimal.

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10 hours ago, Sibiriak said:

A  BMI of 26  with lots of muscle is optimal?    At what  age?   Where's the proof?

I've always thought that guys that walk around with huge amounts of muscle mass and spout that they are "healthy" because of their muscles (and disregard their BMI) are not realizing the full picture when it comes to health and longevity. Having that high of a BMI, regardless of whether one is muscular or fat, entails that the heart has to pump pretty hard to circulate blood. Indeed, a low body fat muscular 26 BMI human will not be likely to get diabetes, but I don't think he/she will be immune to cardiac events.

Perhaps the clearest example of this is in the sport of MMA where the very muscular fighters barely can go more than two rounds without "gassing" out, while the relatively skinny guys with just a tad bit of muscle can go 5 rounds. 

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4 hours ago, alexthegra8 said:

I've always thought that guys that walk around with huge amounts of muscle mass and spout that they are "healthy" because of their muscles (and disregard their BMI) are not realizing the full picture when it comes to health and longevity. Having that high of a BMI, regardless of whether one is muscular or fat, entails that the heart has to pump pretty hard to circulate blood. Indeed, a low body fat muscular 26 BMI human will not be likely to get diabetes, but I don't think he/she will be immune to cardiac events.

J Natl Med Assoc. 2002 Feb;94(2):88-99.
Less is better
Thomas T Samaras, Harold Elrick
PMID: 11853051 PMCID: PMC2594131
Free PMC article
Abstract
The "more is better" credo is evaluated in terms of its harmful ramifications on human health, the environment, and the survival of the human race. The trend towards greater height and body weight in developed countries is evaluated in terms of its negative aspects on health and longevity. The benefits of reduced caloric intake are discussed. Countries that survive on lower food intakes are shown to have much less heart disease, such as South Africa, where rural blacks outlive whites and also have a higher percentage of centenarians. The risks of increasing birth weight are discussed in terms of promoting cancer and overweight in adulthood. Rapid childhood growth also is shown to have risks because rapid maturity is in conflict with the need to have more time to learn about our complex world before reaching reproductive capability. The increase in the average size of humans aggravates our burgeoning population numbers, placing even greater demands on our need for fresh water, energy, resources, and a clean invironment. Many good things come in large packages, such as elephants, whales, and trees. While Sumo wrestlers, football players, and basketball players play an important role in our world, their small numbers do not pose a threat to our survival. However, their body habitus should not be the goal for the average male of the future.

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First of all, a BMI of 26 means, for example, 75 kg in a 170 cm individual, or 80 kg in a 175 kg individual, or 192 pounds in a 6' individual. With a little adiposity (about 10%) that degree of muscularity is remarkable but not overly impressive. It may take time to maintain it, although muscle tissue maintenance is far easier than building muscle. It may take more nourishment and shift the optimization balance toward a more efficient execution of some duties and a less efficient longevity. It may provide more resistance to injuries. There are many aspects to evaluate, I don't know about any specific literature.

17 hours ago, alexthegra8 said:

Indeed, a low body fat muscular 26 BMI human will not be likely to get diabetes, but I don't think he/she will be immune to cardiac events.

That's not even granted. Nourishing those muscles may require lots of carbs and predispose to diabetes. Tolerance will be probably better (dampening of glucose spikes) but it is not granted that fasting glucose will be better. I reached a BMI of 25.6 a few months ago but my fasting glucose increased.

My point is that it's not so easy to evaluate all parameters. A BMI of 26 with an optimal dietary regimen which allows optimal blood glucose, optimal lipids, optimal blood pressure, avoids inflammation and includes some periodic fasting, little stress, optimal sleep may sure have its longevity advantages.

Edited by mccoy

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6 hours ago, mccoy said:

First of all, a BMI of 26 means, for example, 75 kg in a 170 cm individual, or 80 kg in a 175 kg individual, or 192 pounds in a 6' individual. With a little adiposity (about 10%) that degree of muscularity is remarkable but not overly impressive. It may take time to maintain it, although muscle tissue maintenance is far easier than building muscle. It may take more nourishment and shift the optimization balance toward a more efficient execution of some duties and a less efficient longevity. It may provide more resistance to injuries. There are many aspects to evaluate, I don't know about any specific literature.

That's not even granted. Nourishing those muscles may require lots of carbs and predispose to diabetes. Tolerance will be probably better (dampening of glucose spikes) but it is not granted that fasting glucose will be better. I reached a BMI of 25.6 a few months ago but my fasting glucose increased.

My point is that it's not so easy to evaluate all parameters. A BMI of 26 with an optimal dietary regimen which allows optimal blood glucose, optimal lipids, optimal blood pressure, avoids inflammation and includes some periodic fasting, little stress, optimal sleep may sure have its longevity advantages.

Very good points! 

For what its worth, I always felt better w/ less muscle mass but being in good "cardio" shape after bouts of long sessions of cardio for extended weeks at a time; I am surely in the low BMI camp in this regard. Another dynamic worth considering is that lots of muscle usually is correlated with more weight lifting which itself is correlated with higher arterial pressure.

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Muscle masks fat risk

The study looked at data collected from more than 11,500 adults who participated in the National Health and Nutrition Examination Survey (NHANES) between the years 1999 and 2004. (NHANES is a federal survey done annually to evaluate Americans' diets and health.) All participants in that survey had their BMI calculated from their height and weight, and their muscle mass was measured by a body scan.

The results suggest that prior research using BMI has likely underestimated the risk associated with excess body fat, Abramowitz said. That's because when BMI is used as an index, it doesn't distinguish between a person's fat mass and muscle mass, so having more muscle will raise BMI as much as having more body fat; this masks the risks of increased body fat, he said.

The new study's findings show that by accounting for muscle mass in the analysis, the "obesity paradox" goes away, Abramowitz said. In other words, when people with low muscle mass are excluded from the analysis or when differences in muscle mass are taken into consideration, the risks associated with high BMI are magnified and the level of BMI linked with the greatest chance of living longer shifts downward toward a normal weight, he explained.

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Adding to my previous comment on reverse causality of low BMI, here's an article discussing BMI and mortality which I'm not sure if it's been posted already: Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3·6 million adults in the UK

gr2_lrg.jpg

 

As I expected, there's strong reverse causality in cancers related to the digestive and metabolic systems (oesophageal, stomach, liver), while mortality is lower in all other categories for lower BMI. Diseases in these systems are strongly associated with weight loss. There's similar trend in other diseases as well especially mental and neurological disorders and injuries/suicide.

What about respiratory infections? An article discusses the relation:

Quote

Several studies in children or adults suggest that both underweight and obesity are associated with increased infection risk. However, confounding factors such as malnutrition, hygienic status and underlying disease or co-morbidities might aggravate accurate assessment of the impact of body weight on infection risk.

Back to the first article:

Quote

The raised risks of many outcomes at low BMI, coupled with the fact that mental health conditions showed the strongest inverse associations with low BMI, might indicate pervasive effects of mental health problems on a range of outcomes, through pathways that could include poorer self-care and less access to or use of health-care services, or both. The persistence of inverse associations between BMI and deaths from self-harm and interpersonal violence even in sensitivity analyses in which follow-up was started up to 10 years after BMI recording, or when individuals with previously recorded mental illness were excluded, argues against reverse causality. However, it remains possible that depression and related diseases leading to appetite suppression even over a long time period or without a formal diagnosis could partly explain this finding [I wouldn't be surprised if the majority of people with poor mental health DON'T have a formal diagnosis]. Imposing a longer period between BMI recording and study entry tended to attenuate associations between low BMI and outcomes; this might have been observed because a side-effect of this approach is to reduce the amount of person-time included at young ages, and we separately found the strongest associations between low BMI and mortality to be in younger people. The analyses stratified by age also suggested that mortality was minimised in older individuals at higher BMI, perhaps indicating increased importance of nutritional reserves in older age. This finding might suggest that healthy weight recommendations need to account for age, but further work is needed to establish whether increased weight is actually beneficial for older individuals: there is increased risk of reverse causation in older people because of the increased prevalence of most diseases, and BMI might be compromised as a measure of adiposity in the oldest individuals because of complications from loss of muscle mass.

Look at the above graph again and consider that when the confounding factors are attenuated, it's likely that lower BMI results in lower overall mortality of all causes, especially at old ages:

gr3.jpg

The reality is that among the most common mortality-causing illnesses, more of them are likely to cause weight loss than weight gain. And since the majority of UK population (in case of this study) are in normal to overweight category, it causes the overall curve to shift upward on the left side. You might be wondering, doesn't the same apply to 1970s? As I said above, today's population has a general shift to higher BMI. Majority of "naturally healthy" people are in the normal to overweight BMI category, and so today's low BMI is more commonly caused by other abnormal factors instead of being result of natural lifestyle as is more so the case in 1970s.

Look at the green line above and imagine it lowered on the left end with reverse causality attenuated, and the curve shifted leftward overall (due to today's overall BMI rightward shift). Now the 18 BMI of 1970s makes more sense. Just try not to fall when you walk up the stairs.

Edited by Aaron

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On 8/19/2021 at 3:19 AM, Aaron said:

The reality is that among the most common mortality-causing illnesses, more of them are likely to cause weight loss than weight gain. And since the majority of UK population (in case of this study) are in normal to overweight category, it causes the overall curve to shift upward on the left side.

Yep. It goes back further than the 1970s. The US population was getting taller and heavier for a while, now it's actually getting shorter and even fatter.
 

The evolution of BMI values of US adults: 1882-1986

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