Beyond obesity

[DSeid]

Interesting JAMA editorial last week (unfortunately mostly behind wall) that I thought many here would like to be aware of: "Beyond the Obesity Paradox in Diabetes. Fitness, Fatness, and Mortality"

It was inspired by this article in the same issue that noted that the roughly 12% of those who are normal BMI at time of diagnosis with diabetes had a worse mortality rate than those who were overweight or obese at time of diagnosis. To me that seems almost like a no duh: if you have diabetes with a healthy level of fatness then you both have a different make up than someone who only develops diabetes at a higher fat level (be it by a genetic cause or an epigenetic cause) and if nothing else weight loss alone is less likely to be helpful. But the editorial uses it as cause to riff on something else, which even if not the main issue for this particular finding is one who many here will be glad to see the mainstream medical rag embracing: the issue of the "metabolically obese normal-weight (MONW)" Overlapping mightily with what gets more popularly called the "skinny fat."

Individuals who are MONW are becoming more common, as reported in an analysis from the National Health and Nutrition Examination Survey (NHANES): 23.5% of normal-weight adults in the United States (8.1% of the overall population) were metabolically abnormal.7 Furthermore, individuals with normal BMI but high body fat content (MONW-like) have higher cardiovascular mortality, particularly among women.8 The results reported by Carnethon et al5 also are consistent across minority groups with MONW, including Asian American individuals. This has broad significance in view of the global effects of diabetes, with an accelerating epidemic in Asian populations. This increase in diabetes prevalence is in part related to the emergence of the MONW phenotype, with data from the Korean NHANES showing the MONW phenotype in 12.7% of normal-weight persons (8.7% of the overall population).9

Sarcopenic obesity is defined by high body fat in the presence of reduced lean body mass and is associated with a reduction in cardiorespiratory fitness and physical function, which in turn leads to mobility disability and premature death.10 The study by Carnethon et al also highlights a potential role for lower lean mass and increased waist circumference (ie, sarcopenic obesity) in the higher mortality eventually seen in normal-weight individuals at the time of diabetes development. In their analyses, larger waist circumference was associated with increased total mortality, yet normal BMI remained significantly associated with mortality after adjustment for waist circumference, supporting contributions from both high body fat and low lean body mass. In a systematic review, the risk for all-cause and cardiovascular mortality was lower among individuals with high BMI and good aerobic fitness than in individuals with normal BMI and poor fitness.11 This phenomenon has also been reported in a study of veterans with diabetes in which the obesity paradox was observed along with an independent association between poor exercise capacity and mortality within BMI categories.12 Improved knowledge of the effects of body composition, fat distribution, and physical function, beyond the measurement of BMI, will help the medical and scientific community better understand the relationships among obesity, morbidity, and mortality in adults with diabetes. ... Recent data from the Look AHEAD (Action for Health in Diabetes) study also showed that intentional weight loss and improved fitness can slow the decline in mobility in overweight adults with type 2 diabetes.17 Therefore, a combination of exercise and modest calorie restriction appears to be the optimal method of reducing fat mass and preserving muscle mass ... Low cardiorespiratory fitness and inactivity may impose a greater health threat than obesity. Therefore, more emphasis should be placed on investigating the benefits incurred by increasing physical activity and fitness as a strategy to improve quality of life and reduce mortality risk in the increasing population of individuals with diabetes in the United States and abroad.

Thoughts or reactions?

[Michael63129]

It sounds like another complication of an increasingly sedentary world; people who have a normal body weight but low muscle mass and consequently too much body fat for their weight due to insufficient exercise. In particular, this sentence stands out:

Low cardiorespiratory fitness and inactivity may impose a greater health threat than obesity.

That may also explain the findings of some past studies, such as those that found that being slightly overweight (BMI around 25-27 or so) had a lower risk of mortality than those who were normal weight; somebody who is fat but gets regular exercise can be healthier than somebody who is thin but never exercises.

[yorick73]

Well, we know obesity is associated with metabolic abnormalities. I can't read the article but it appears to imply a problem with BMI in individuals who have high fat content and low lean mass. That seems like common sense...BMI is a blunt instrument and maybe better methods are necessary to identify those at risk.

I'm not clear exactly what you are getting at? Do you have some issue with this editorial?

[DSeid]

Actually I am pleased with the editorial. I shared it because of two main recurring and intertwined discussions that occur on these boards: how blunt of an instrument is BMI; and weight being set up as the goal rather than fitness.

1) Issues regarding BMI as a measure. For reasons of convenience overweight and obesity are defined by BMI levels and for tracking population trends it is a fairly good tool. This editorial represents the increasing understanding and greater acceptance of the need to utilize BMI at an individual level in a manner more sophisticated than that. The BMI is screening tool that will miss some who are normal by BMI but are still "metabolically obese" and will, if used as the definition of the problem (rather than identifying someone at being at higher risk of having unhealthy habits and lower fitness), have an unappreciated false positive rate.

2) Many threads here have posters hyperfocused on weight loss as their goal or others telling them that it should be their goal and that achieving such is a simple thing to do. In a recent thread one poster advised an op that his mother with abdominal obesity needn't bother much with exercise because exercise won't help her lose much weight. I think the attitudes of many docs only exacerbate the focus on the weight, the scale, as the goal. Like BMI the weight is easy to measure and easy to follow. My hope is that this editorial helps them recognize the quote highlighted by Michael63129 above and the data that shows that not only can someone who is fat but fit be healthier than someone who is skinny but unfit; they are:

In a systematic review, the risk for all-cause and cardiovascular mortality was lower among individuals with high BMI and good aerobic fitness than in individuals with normal BMI and poor fitness.

[TheTerribleTako]

Thanks for the article, DSeid. I don't have much to add on this topic, but you always seem to have up to date information and you always explain it with much clarity in a field that's often full of noise misinformation. As someone who mostly lurks on this board, I really appreciate your posts and analysis on topics related to obesity and health. I wish more doctors were like you.

[don't ask]

The thing that most surprises me about scientific research is how many of the findings are of the "sun rises in the East" variety. Nothing in that editorial is at all novel. I recalling seeing this book at a friend's a couple of years ago and surely something like
Top 10 Reasons Why The BMI Is Bogus from NPR should have heralded the death knell of using BMI as a measure. But I routinely see pieces lauding new research that is not new or novel at all.

[Enkel]

From Don't Ask's second link:

8. It makes the more cynical members of society suspect that the medical insurance industry lobbies for the continued use of the BMI to keep their profits high.

Insurance companies sometimes charge higher premiums for people with a high BMI. Among such people are all those fit individuals with good bone and muscle and little fat, who will live long, healthy lives during which they will have to pay those greater premiums.

I believe this one. I've always had a problem with BMI. I'm a dense sort of person and when ever I have to be weighed, they always do that double-take on the scale. When I had insurance, you can bet that I got charged more for their BMI calculation, despite the fact that I could unload and stack nearly 8 tons of hay at one go and daily carried four 100 pound bales on my back the 300 feet from the barn to the field.

[MsRobyn]

I've been exercising a good bit lately. Most of it is aerobic exercise, and I try to mix in some weight-bearing stuff like walking to make things interesting. I've been able to do around 25 miles on hilly road on my bike, and my walking speed has definitely increased, from around 2.5 miles per hour to 3.5+ miles per hour. My endurance has never been this good ever, and that includes after Navy boot camp. (I'm dealing with some residual respiratory issues due to not smoking, which isn't helping that much, but the exercise is clearing the crap out of my lungs as is the fact that I live in a humid climate. But I digress.)

That being said, my overall weight loss has stalled out, which is disappointing. Exercise increases my hunger, and even though I'm trying to make good choices (fruit and sugar-free Jello, for example), my weight loss has apparently stalled out a bit due to a combination of emotional eating and probably the exercise. And, thanks to the exercise, I look much better than I ever have, except maybe after boot camp. But Weight Watchers is myopically focused on BMI, as well, and I can't achieve my goal weight until I lose those last pounds. It's pretty damn frustrating.

[DSeid]

don't ask,

Thing is that the BMI is not bogus. And there is a big difference between sensationalized articles claiming such a thing, distorting how the modern use of BMI developed and playing to silly conspiracy theories, and the AMA mouthpiece journal promoting a more nuanced usage of the tool. That NPR list is very stupid (if you want I could go down point by point). There is also a big difference between this editorial's points and a book that tells people to "eat what you want, when you want, enjoy pleasurable foods ..." Focusing the fight on fitness and the nutritional plan rather than on the scale is not the same as advising people to "give up the fight."

Yes information about MONW has been being published for years and BMI was always known in the literature to be a convenient to use rough correlate of adiposity, particularly good at identifying the obese. Yes, information about the importance what sort of adiposity has been accumulating for years. Nothing "novel", but still something significant.

As a screening tool BMI is pretty dang good. It was the step of using BMI as the definitions of overweight and obesity at an individual level that was regrettable and more importantly the focus on fatness over fitness.

MsRobyn,

The fact that you look so much better and have so much better endurance are proof that you've lost fat and become more fit. The point of this editorial is an endorsement of the POV that the scale is a poorer correlate for your health outcomes than those two, especially the latter one. It is the case that fitness is harder to measure in a Weight Watcher meeting or at a doctor's visit than weight or BMI and thus those numbers will continue to be used. But you have to accept that your goal is not the weight number. It is the better health in both the short and long terms and that is being achieved by what you do, not what you weigh.

[ultrafilter]

Originally Posted by DSeid

That NPR list is very stupid (if you want I could go down point by point).

Please do. There's way too much ignorance on the topic of BMI, and it would be nice to have something authoritative.

Anyway, the discussion here reminds me of something else I've seen recently, which is the notion that lack of exercise should be considered a medical condition in and of itself. I can buy their arguments pretty easily.

[RadicalPi]

Originally Posted by ultrafilter

Please do. There's way too much ignorance on the topic of BMI, and it would be nice to have something authoritative.

You didn't ask, but here's my opinion. Also, I didn't comment on all ten.

2. BMI “ignores waist size, which is a clear indicator of obesity level.” I was under the impression that BMI is a quick and dirty way to guess someone’s waist line when that information isn’t available. (See http://www.maa.org/devlin/devlin_05_09.html) So, obviously, BMI is going to have all the flaws of the waist line measurement, with a few more on top of it.

5. I can’t believe the vast majority of people in about 1850 lived sedentary lives. There is simply no way that is true.

6. The BMI is not a number between 1 and 100. I have no idea why the article would assume it is. A BMI of 100 for a 6’0” man would mean a weight of 738 pounds. Clearly that is very high, but there’s no reason why weight couldn't keep climbing past that.

7. The idea of sharp boundaries is of course nonsense except insofar as you have to draw lines somewhere. Stuff like this happens in almost everything humans do and likely happens as well in whatever might replace the BMI.

[DSeid]

The BMI is far from perfect but sometimes the critics really do let the perfect be the enemy of the good. It is a screening test with limitations which works well to identify those at high risk of high adiposity.

Some resources:

About Quetelet and the development of the Index He set out to develop a tool that spread weight to height in a normal distribution and did so. In recent decades it was found that it was still valid and correlated well with obesity related outcomes.

One of the first studies to confirm the validity of the Quetelet Index in epidemiological studies comprised data gathered during the fourth examination of the Framingham study [6]. In a subsequent comparative study of available indices of relative weight and obesity published in 1972, Ancel Keys (1904–2004) confirmed the validity of the Quetelet Index and named it the Body Mass Index (BMI) [7]. Since then, as evidence of the association of obesity with various diseases continues to accrue, the BMI has been used as an expression to report the link of excess relative weight to morbidity and mortality. Primarily derived from data obtained on Anglo-Saxon populations, the generalizibility and applicability of the BMI and its cut-off points to other populations has been questioned and its sensitivity as a measure of excess fat queried. Nevertheless, it remains a dependable value and the basis of much of the associations reported heretofore with obesity

The AHA statement on Assessment of Obesity.

BMI, calculated as body weight in kilograms divided by height in meters squared (kg/m2), is one of the most commonly used anthropometric measures to assess for total body adiposity. Because of its simplicity as a measure, it has been used in epidemiological studies and is recommended as a screening tool in the initial clinical assessment of obesity.143,144 Multiple epidemiological studies have demonstrated increased morbidity and mortality with BMI >30 kg/m2.145 Data from the Prospective Studies Collaboration, which analyzed 900 000 adults, demonstrated a 30% increase in all-cause mortality for every increase of 5 U in BMI above a BMI of 25 kg/m2.20

Although the utility of BMI has been borne out in epidemiological data, there are limitations to the use of BMI alone to assess for adiposity in clinical practice, particularly among adults with BMI ≤30 kg/m2.146 ... BMI should be considered as the primary tool for the assessment of body fatness in clinical practice because of its global acceptance and ease of calculation. The limitations of the BMI as discussed, however, must be considered when it is used alone as an index of adiposity in clinical practice.

That statement goes into detail on other possible methods as well and the only one that they think might also meet the requirements of reliability, reproducibility, and ease of use across all populations, may be waist circumference, but at this point it is best viewed as a complement to BMI, not a replacement for.

In summary, WC is a simple and inexpensive tool for assessing body fat distribution. It correlates well with abdominal obesity as assessed by imaging methods (discussed below) and is associated with increased risk for adiposity-related morbidity and mortality. This tool requires only the purchase of an appropriate tape measure and simple training of health professionals and/or assistants. It can easily be incorporated in the vital sign assessment of patients at the time the body weight is obtained. We recommend performing the WC measurement at the iliac crest as the easiest and most consistent location, as described by the National Institutes of Health guidelines. This tool and its importance can be explained easily to patients. For these reasons, WC is an ideal inexpensive clinical complement to the BMI measurement.

This guideline is more what I need as a pediatrician. And the information gained by following the BMI curve, rather than focusing on a single measurement, is invaluable, even in preschool years.

So let's go through the points:

As the Weekend Edition math guy, I spoke to Scott Simon and told him the body mass index fails on 10 grounds:

1. The person who dreamed up the BMI said explicitly that it could not and should not be used to indicate the level of fatness in an individual.

The BMI was introduced in the early 19th century by a Belgian named Lambert Adolphe Jacques Quetelet. He was a mathematician, not a physician. He produced the formula to give a quick and easy way to measure the degree of obesity of the general population to assist the government in allocating resources. In other words, it is a 200-year-old hack.

The tool was validated in modern populations. Who cares if a tool is old if it works? The microscope was invented a long time ago; does it not work now because of that?

2. It is scientifically nonsensical.

There is no physiological reason to square a person's height (Quetelet had to square the height to get a formula that matched the overall data. If you can't fix the data, rig the formula!). Moreover, it ignores waist size, which is a clear indicator of obesity level.

3. It is physiologically wrong.

It makes no allowance for the relative proportions of bone, muscle and fat in the body. But bone is denser than muscle and twice as dense as fat, so a person with strong bones, good muscle tone and low fat will have a high BMI. Thus, athletes and fit, health-conscious movie stars who work out a lot tend to find themselves classified as overweight or even obese.

It is an observed correlation. Period. Someone with a BMI over 30 is highly likely to have high adiposity and be at risk of obesity related health problems. Few with BMI over 30 are "athletes and fit, health-conscious movie stars who work out a lot". Maybe a few bodybuilders, but a very few. Saying that is scientific nonsense evinces a serious lack of understanding of science.

Waist circumference is a measure of central obesity which may be the most important thing to know but as of now we cannot say it is the only important thing to know.

4. It gets the logic wrong.

The CDC says on its Web site that "the BMI is a reliable indicator of body fatness for people." This is a fundamental error of logic. ...

Nope. Very logical. If someone has a high BMI and I should be suspicious that they have high adiposity and are at high risk of having behaviors that should be changed. It won't catch all of those with behaviors that should be changed and it will be wrong for many too. But it catches a good many.

5. It's bad statistics.

Because the majority of people today (and in Quetelet's time) lead fairly sedentary lives and are not particularly active, the formula tacitly assumes low muscle mass and high relative fat content. It applies moderately well when applied to such people because it was formulated by focusing on them. But it gives exactly the wrong answer for a large and significant section of the population, namely the lean, fit and healthy. Quetelet is also the person who came up with the idea of "the average man." That's a useful concept, but if you try to apply it to any one person, you come up with the absurdity of a person with 2.4 children. Averages measure entire populations and often don't apply to individuals.

Huh? So because populations are similar then and now it is not valid as a screen? Again, it should not be considered the whole story.

6. It is lying by scientific authority.

Because the BMI is a single number between 1 and 100 (like a percentage) that comes from a mathematical formula, it carries an air of scientific authority. But it is mathematical snake oil.

7. It suggests there are distinct categories of underweight, ideal, overweight and obese, with sharp boundaries that hinge on a decimal place.

That's total nonsense.

Agreed that the cut-offs are arbitrary and that 25 would have always over-identified too many as overweight. It was a silly choice to make it easy for people to use..

And as said above, does this guy even know what the BMI is? 1 to 100? Maybe he's thinking of percentiles.

8. It makes the more cynical members of society suspect that the medical insurance industry lobbies for the continued use of the BMI to keep their profits high.

Insurance companies sometimes charge higher premiums for people with a high BMI. Among such people are all those fit individuals with good bone and muscle and little fat, who will live long, healthy lives during which they will have to pay those greater premiums.

An insurance company wants to screen out populations at higher risk and those with BMI over 30 are, as a population, at higher risk. If they are allowed to cherry pick the lowest risk group then of course they will.

9. Continued reliance on the BMI means doctors don't feel the need to use one of the more scientifically sound methods that are available to measure obesity levels.

Those alternatives cost a little bit more, but they give far more reliable results.

He wants us to MRI or hydrostatically weigh every person? The only contender for screening purposes (quick, cheap to use, reproducible, decent enough predictive value for obesity complications ...) is waist circumference. Yes, that should be used more often, but for now at least as an adjunct to BMI. It is too soon to say it is good enough alone.

10. It embarrasses the U.S.

It is embarrassing for one of the most scientifically, technologically and medicinally advanced nations in the world to base advice on how to prevent one of the leading causes of poor health and premature death (obesity) on a 200-year-old numerical hack developed by a mathematician who was not even an expert in what little was known about the human body back then.

What embarrasses the U.S. is the level of morbid obesity. Those with BMI over 35 are fat, not muscled, and those numbers have sky rocketed.

BMI is a limited tool and its limits need to be better appreciated by both the public and by clinicians. But "bogus"? Hogwash.

[rhubarbarin]

I think this supports my personal distaste for BMI being used as a health measure. 'Fatness' is something far more complicated than weight relative to height. I think newer, more reliable methods of determining body fat percentage should be emphasized.

[DSeid]

Another study. (And the article it references.)

"Once fitness is duly accounted for and an accurate measure of adiposity is used, the metabolically healthy but obese phenotype is a benign condition, with a better prognosis (30% to 50% lower risk) for mortality and morbidity than metabolically abnormal obese people," say Dr Francisco Ortega (Karolinksa Institute, Stockholm, Sweden) and colleagues in the report, published online September 5, 2012 in the European Heart Journal. "Interestingly, no difference in the prognosis is observed between metabolically healthy but obese individuals and metabolically healthy normal-fat individuals once fitness is accounted for, suggesting a key role of fitness in these associations."

[DSeid]

Another one.

The obesity paradox refers to the epidemiological evidence that obesity compared with normal weight is associated with counter-intuitive improved health in a variety of disease conditions. The aim of this study was to investigate the relationship between body mass index (BMI) and mortality in patients with acute coronary syndromes (ACSs).Methods and resultsWe extracted data from the Swedish Coronary Angiography and Angioplasty Registry and identified 64 436 patients who underwent coronary angiography due to ACSs ... Regardless of angiographic findings [significant or no significant coronary artery disease (CAD)] and treatment decision, the underweight group (BMI <18.5 kg/m(2)) had the greatest risk for mortality. Medical therapy and PCI-treated patients with modest overweight (BMI category 26.5-<28 kg/m(2)) had the lowest risk of mortality [hazard ratio (HR) 0.52; 95% CI 0.34-0.80 and HR 0.64; 95% CI 0.50-0.81, respectively]. When studying BMI as a continuous variable in patients with significant CAD, the adjusted risk for mortality decreased with increasing BMI up to ∼35 kg/m(2) and then increased. In patients with significant CAD undergoing coronary artery by-pass grafting and in patients with no significant CAD, there was no difference in mortality risk in the overweight groups compared with the normal weight group.ConclusionIn this large and unselected group of patients with ACSs, the relation between BMI and mortality was U-shaped, with the nadir among overweight or obese patients and underweight and normal-weight patients having the highest risk. These data strengthen the concept of the obesity paradox substantially.

And the take on it. I think this may go farther than the data warrants but is worth sharing.

Those who were deemed overweight or obese by body-mass index (BMI) had a lower risk of death after PCI than normal-weight or underweight participants up to three years after hospitalization, report Dr Oskar Angerås (University of Gothenburg, Sweden) and colleagues in their paper, published online September 5, 2012 in the European Heart Journal.

"In patients who have a chronic disease, obesity seems to have some kind of protective effect—what this is we don't know, it's difficult to say," coauthor of the new research, Dr Kristjan Karason (University of Gothenburg, Sweden), told heartwire.

In an accompanying editorial [2], Drs Stephan von Haehlin, Oliver Hartmann, and Dr Stefan D Anker (Charité Medical School, Berlin, Germany) agree that this research strengthens the existing evidence for the obesity paradox. They conclude that weight loss in patients with chronic illness and a BMI of <40 kg/m2 "is always bad, and in fact not a single study exists to suggest that weight loss in chronic illness makes patients live longer."

But Karason says he feels this advice is taking things a step too far. He notes that heart-disease guidelines still recommend that patients should lose weight, "and I don't think we have enough data to answer the question of whether these patients should not lose weight." Still, he says, "perhaps we should be less worried about patients who are overweight and have chronic diseases, as they seem to do fairly well." But he says this stance does not extend to the extremely obese (BMI>35 kg/m2). While he and his colleagues did not have enough patients in this category to draw any firm conclusions, "I would recommend those with BMI >35 kg/m2 to lose weight because they have a lot of other problems, comorbidities, and poor quality of life," he observes.