Does Weight Matter?

Determining the net health effects of independent factors can be tricky, especially when those factors cannot be controlled for in experimental studies. For things like body mass index (BMI) we must rely on observational data and triangulate with multiple studies to isolate the contributions from BMI. But it can be done.

The data, however, are likely to be complex and noisy, and therefore there is plenty of opportunity for ideology to trump objectivity in interpreting the data. There are those who, for whatever reason, deny that we are having an obesity epidemic in the West, and those who deny the health implications of being overweight as an independent factor.


The terms overweight and obesity have had various definitions in the past, but in recent years the various health organizations have settled on consensus operational definitions (for obvious practical reasons). Their definition relates to body mass index, which is a person’s weight in kilograms (kg) divided by their height in meters (m) squared.

It should be noted that BMI is a measure of weight, not fat (adiposity). BMI is used for convenience, as height and weight data are often available, but more direct measures of body fat are not. It is widely recognized and admitted that BMI is problematic as applied to individuals. Muscular and athletic people may have a high BMI and not have excess adiposity, for example. Also at the extremes of height the BMI becomes harder to interpret.

But this does not mean the BMI is useless. In fact, for most people BMI correlates quite well with adiposity. In one study researchers compared BMI to a more direct measure of body fat percentage using skin-fold thickness. They found that when subjects met the criterion for obesity based upon BMI, they were truly obese by skin-fold thickness 50-80% of the time (depending on gender and ethnicity). When they were not obese by BMI they were not obese by skin-fold 85-99% of the time.

So BMI is a rough but useful estimate, good for large epidemiological studies where more elaborate fat percentage measurements are not practical. However, those who wish to deny the “obesity epidemic” have found BMI to be a convenient target for sowing doubt.

There is ongoing research into the utility of supplementing BMI with other easy measures, like waist circumference. This seems to be a more accurate measure of adiposity, and specifically risk from being overweight. So going forward we may see more meaningful measured routinely captured, and BMI may be replaced or supplemented with these measures. But for now we will continue to see many studies based upon BMI.

Overweight and Obese

Because BMI is a convenient measure, it has become the measure of choice in defining overweight and obesity. For children and adolescents overweight is defined as a BMI in the 85-95% percentile by age and gender, while obesity is >95% percentile BMI. For adults overweight is defined as a BMI of >=25.0 but <30.0, obese is defined by BMI >=30.0 and < 40.0, and extremely obese is defined as BMI >=40.0.

These cutoffs, like all such cutoffs for medical definitions, are partly arbitrary (they constitute drawing a line to demarcate a spectrum) but are evidence- based. This is similar to definitions for hypertension, for example. Researchers typically will set the cutoff to capture most people who are at risk for medical complications.

This is where the controversy comes into play with overweight and obesity. In 1998 the NIH decided to lower the cutoff for BMI for overweight, from 28 for men and 27 for women to 25 for both sexes. This was based upon an expert panel review of hundreds of studies. It also brought the NIH definition in line with the World Health Organization and other health organizations. The BMI 25 cutoff has now become generally accepted. The cutoff for obesity was not changed – it was and remains a BMI of 30.

Of course this means that any estimates of overweight (but not obesity) based upon the newer lower cutoff of BMI 25 would be greater than estimates based upon the previous criteria. This raised a bit of a kurfuffle, as it always seems to do when medical definitions are altered. This happened with the lowering of the cholesterol cutoff, blood pressure for hypertension, and blood sugar for diabetes.

This event in 1998 now has become a central argument in the arsenal of obesity deniers. If you search on “obesity statistics”, on the first page you will get this apparent libertarian site which quotes a “food industry spokesman” as saying:

In 1998, the U.S. Government changed the standards by which body mass index is measured. As a result, close to 30 million Americans were shifted from a government-approved weight to the overweight and obese category, without gaining an ounce, Burrita said.

This is slightly misleading, as the obese category was not changed. But the main point is that this 1998 redefinition is being used to argue that the obesity epidemic is all smoke and mirrors. The article goes on to quote this gem from William Quick:

According to an American Medical Association report, 14.5 % of Americans in 1980 were obese, a total of 32,700,000 (based on a population of 226,000,000). If, as the above article states, the numbers of obese Americans have “doubled” in the past twenty years, this would mean there are now about 66 million of them. But thirty million of those fatties were created by a change in definition, so by the standards of 1980 [we would calculate an] obesity percentage of 12.85 percent, an actual decrease in obesity percentage since 1980.

That’s some massively flawed reasoning. Again we see the confusion of the overweight and obese categories. But also there are many false assumptions in that back-of-the-envelope calculation. Quick is mixing statistics from different sources and contexts, and the result is a mess.

What we really need is a look at the numbers over time using the same definition. Fortunately, most epidemiologists are not dolts and they get this very basic concept. In fact, it doesn’t get much more basic than this, and it would take some pretty naive incompetence to use inconsistent definitions over time.

The CDC has crunched the numbers for us, and using the modern cutoffs for overweight, obese, and extremely obese applied to BMI data for the last few decades they document a pretty steady increase in American fatness over time. Take a look at the video on the site to see this data presented graphically. Also, it is summarized in the graph here.

As you can see, the lines go steadily up – with the exception that the overweight category has decreased in the last decade. However, it seems that this is due to the shifting of people from the overweight category to the obese category, not to the normal weight category.

Of course, you could cherry pick by just looking at the overweight category. Looking at all the data, however, tells the real story.

The Health Risks of Overweight

Is being overweight and obese an independent risk factor for any specific illness? The answer is an overwhelming yes. There are many diseases for which being overweight is a risk factor, such as type II diabetes, obstructive sleep apnea, pseudotumor cerebri, heart disease, and other illnesses. The data is clear – but complex, and so allows for those motivated to deny the connection to distort and cherry pick the data to create the impression they wish.

From a website advocating size acceptance we read:

There is actually no evidence that being fat will give you diabetes or cancer or PCOS or any other health issues. Being obese tends to correlate with some health problems, but the causes of the health problems may be multiple, and they certainly aren’t thoroughly understood in current medical research.

It must be pointed out that many obese people are perfectly healthy, if you look at the numbers that matter. This seems to refute the idea that fat alone causes artery clogging, diabetes, or anything else it’s often blamed for – clearly, there are at least other factors besides fat, and it may even be the case that fat’s nothing to do with it at all. As long as your other numbers are good, your weight does not impact your health. If you can possibly afford to get your numbers tested once a year, or even every few years, do so. If the numbers that matter are good, your weight is fine

Here we see a couple of logical fallacies. The first is the denial of cause based upon an overapplication of the “correlation does not equal causation” fallacy. It is true that correlation alone does not prove causation, but causation may be the answer, and we can test this hypothesis by testing multiple correlations. For example, if weight is reduced will the risk of the disease decrease.

Also, the fact that being overweight and obese may cause health problems through intermediary effects is irrelevant. If being overweight causes insulin resistance which causes diabetes, it is not meaningful to say that weight is not causing diabetes.

We also see confusion between weight as a risk factor vs being an absolute cause. Weight is one factor among many, such as genetics. There are obese people who are otherwise healthy, just like there are heavy smokers who never get lung cancer. This is entirely irrelevant to the claim that weight is a risk factor for various diseases. The lack of 100% correlation does not justify the conclusion that weight has “nothing to do with it at all.”


There is an obesity epidemic in the US and in developed nations generally, and this increase in adiposity is an independent risk factor for many diseases and disorders. Exactly what role weight is playing in specific diseases is a complex question that is the subject of ongoing research, but there is already overwhelming data in many condition to show that being overweight is a health risk.

Further – this has nothing to do with size acceptance. We can separate the question of social stigma from the medical facts. It is also folly to tie a social/ethical issue to a specific factual premise – because when the facts don’t come out the way you wish that either weakens your ethical stance, and/or forces you to deny the scientific facts. We can simultaneously treat overweight and obesity as the health problem that it is, while addressing the social and psychological aspects of weight in our society.

Posted in: Public Health

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39 thoughts on “Does Weight Matter?

  1. Bacteriophile says:

    Thanks for this summary. I do often hear people talking about how BMI is not a good measurement on which to base health advice, and how body fat or possibly waist circumference/waist-hip ratio are better.

    Also, I have looked at a number of papers examining the correlation between BMI and stuff like mortality or disease in large numbers of people, and many of them seem to indicate that slightly overweight people (BMI ~25) have less risk (for example, this paper:

    What do you think of these ideas?

  2. BMI is useful in the aggregate, but not applied to individuals, where other factors need to be considered, and other measures are far more accurate.

    One problem with BMI is that very muscular people will have an increased BMI, and this contaminates the overweight category and may be responsible for the fact that being slightly overweight correlates with better health outcomes.

    Also, the normal weight category is contaminated with people who have lost weight because they are sick.

    It is also plausible that having 10-20 extra pounds is not much of a risk factor, and may provide some health benefit in terms of caloric reserve, better protection for organs, etc.

    We need more data to sort this out.

  3. blu says:

    That chart just screams out to be done as an area chart.

  4. WilliamLawrenceUtridge says:

    Because BMI is a convenient measure, it has become the measure of choice in defining overweight and obesity. For children and adolescents overweight is defined as a BMI in the 85-95% percentile by age and gender, while obesity is >95% percentile BMI. For adults overweight is defined as a BMI of >=25.0 but =30.0 and =40.0

    The definition for kids seems a bit weird – if it’s based on a % rank, it’s not accounting for the possiblity of a generation of kids getting fatter as a whole (as seems to be the case). Are they comparing against a “fixed” generation, or do they adjust the % ranks over time?

  5. It is awesome to see this topic addressed with data and reason.

    My view is that being overweight or obese does not “matter.” There have been many epidemiological studies showing no increased risk of shorter lifespan assoc with being overweight, and the risk for obestiy being modest if anything, and really only notable at higher levels of obesity.

    Zheng NEJM 2011 presents yet another broad review indicating that just because a person is overweight or obese does not mean they will be expected to die earlier. Their “Table 3″ show risk of death, controlling for “reverse causation:” controlling for a person who became obese because they had a health problem (CVD > obestiy, rather than our alarm over possibility of obestiy > CVD), the risk of early death pretty much disappears for obese versus non-obese. [This Table takes some time to interpret: smokers face no elevated risk of death for obestiy – not because weight is not an issue for them, but because their risk of death is elevated by smoking at N BMI as well as elevated BMI.]

    Because of changed computers, I cannot quickly access a couple other broad-scope epi reports on this issue. But I have paid attn to this for several years.

    This is a great issue to examine thru the lens of EBM.

    I frankly do not believe that “we” (health prognosticators) need to admonish an overweight person to “lose weight” simply because they are in the “overweight” range. And this is not really justified for an obese person, either.

    Poor grooming and hygiene is a clue that your patient is not doing well. It is not a health problem in itself. The person may live to a merry old age with poor grooming and hygiene. But if it indicates that they are depressed, or in bad financial shape, then poor health may follow. So, you work with the indicator. But a make-over will not solve the problem.

    The “rise” in obesity is the problem. Our populace is getting less active. Zheng reports epi data from a range of Asian countries. Those populations are carrying out regular physical activity for chores, work, and local travel. They are also eating a range of foods.

    We used to have a certain distribution of BMI in the US, with very modest elevation of risk of early death for obesity. Going into the future, this will change drastically.

    Not because “obesity” predicts earlier death, but because low physical activity and a poor diet indicate risk of early death.

    This is a big deal.

    Many health care providers and systems, and public health campaigns, alarm people that being overweight is the problem.

    It is not.

    Poor diet and inactivit are the problems. If a person is eating fairly well, and getting modest exercise regularly, they can be fat and happy without much worry (ignoring various exceptions such as thyroid disorder).

    Khaw 2008 Plos Medicine illustrates the ‘fit and fat’ issue in another way. They examine whether early mortality is a function of BMI or of health habits. BMI itself is not a habit (needles to say, but worth noting in this context).

    They identifiy 4 health habits that distinguish early vs later death: smoking, alcohol above the 2-glass-a-day level, fruit/veg intake by blood vita C, and low phys activity (sedentary job-plus noleisure time activity).

    Their epi data has a death rate of about 10% across BMI strata (their Table 4). Relative risk of all-cause mortality increases monotonically, independent of BMI level, for those not practicing 1, 2, 3, or 4 identified health behaviors.

    This translates into what public health messages we ought to promote, and what we ought to be saying clinically.

    We should not admonish people to “lose weight.”

    We should figure out easier ways to determine who is “fit and fat” and who has low activity or has poor diet.

    Diet is not too hard to figure out. If the pt. does not know, you just ask: processed foods, and restaurants = poor diet; cooking from scratch and family meals = OK diet. Also you can test vita c level in the pt’s blood. Physical activity is not hard to figure out: first, figure out job, then figure out leisure activity/chores.

    It is more challenging to asssess actual fitness level, but that is maybe where we should head. Max VO2 is hard to measure.

    The benefits of changing our view from “lose weight” to “exercise and quit smoking” is that 1. we espouse change that fits the epidemiology; 2. we encourage something that is feasible, exercise, or eat fruit/veg, versus something that is NOT very likely (“lose weight”); and 3. we could break people from the illusion, from the television commercials of weight loss clinics, supplements and fashion, that beign “overweight” is “unhealthy.”

    The television ads for fitness equipment and supplements thrives off of the heathcare preoccupation with “lose weight.” The woman who exercises and goes from size 8 to size 4 has not avoided early death attributable to BMI. Size 8 was never bad.

    There is a great re-consideration of whether “cholesterol” is bad. Again, my opinion is less founded in data, but I suspect that we will, in the long run, figure out that the real problem is inactivity.

    For our school children, we should be teaching them to always be active, not to watch their waist line. This is very profound for kids, esp at their body-image-sensitive time of life.

    When we emphasize weight as a health problem, we reinforce the aesthetic/social stigma aspect of weight. Fat = “immoral” or “shameful” on the playground and in health class.

    Our weight loss interventions are lousy (cf: Svetkey JAMA 2008) (no offense to the investigators – it was a well-run study – just no one really had a sustained weight loss).

    If we focus on “weight loss,” we will be interested in pharmaceutical management of weight loss. This includes stimulants and drugs like sibutramine, where we have great likelihood of harming people more than helping. And, a perosn who gets to normal BMI with ephedra is not a person who will end up living longer.

    When “weight loss” fails, as it is destined to do, you blow self esteem. You change behavior and experience modest weight loss. Howeer, if the behavior change – more fruit/veg, more exercise, is both the means and the outcome, then the person experiences succes for every increment of change. Jog 2 miles a week, feel a little empowered and successful. Jog 4 miles, feel even more. Snowball effect.

    When is BMI a problem? This is our recent trend – in our wealth, we find it easy to get calories, entertainment, and income without expending much energy. A person who gets to be “overweight” in mid-life, but stays active might have an aesthetic problem, but they are relatively safe from shorter life. A kid who is “overweight” in 3rd grade is diabetes waiting to happen.

    This is just beginning to show up on our post-WWII prosperity epidemiology. The person born in 1960, raised in the wealth of their WWII parents, is just getting into 50s.

    We don’t need to “hammer” the weight issue. We need to hammer the inactivity.

    We need to ignore the scale.

    We need to assess physical capacity by easy means such as the “Long Distance Corridor Walk.”

    We need to do blood test for vita C.

    We need to follow five-A’s for smoking.

    Plus, this blog stimulates me to consider: we may need to encourage body size acceptance.

    Those changes are not really all that drastic. They can all be done in “primary care” as long as a 20-meter corridor is around.

  6. Gregory Goldmacher says:

    Because weight is an issue that ties in to people’s ideas about attractiveness, success, and morality (self-control), it’s not surprising that any science/fact based discussion is going to have to fight uphill constantly against aggressive misinterpretation of the data by people who are not primarily interested in the science itself, but in what they see as social, moral, and political implications.

  7. For the average healthy adult, being just 10-20 pounds overweight is not a disease risk factor to worry about. We don’t need more research on that.

    A far more interesting issue is whether losing excess weight reduces the risk of death. It has been surprising difficult to prove that. In fact, patients with coronary heart disease, heart failure, and chronic kidney disease live longer if they’re overweight, even mildly obese. It’s called the “obesity paradox.”

    I blogged about this issue here, for anyone interested:


  8. Bacteriophile says:

    But even if obesity is an indicator of poor health rather than a cause (which seems possible but I’m not sure if it’s true), obviously there are some problems that are caused simply by carrying too much extra weight (joint problems, sleep apnea, etc), so it’s never completely harmless.

  9. Oh, I shouldn’t take the time, but…

    I have a personal goal of avoiding joint or disc surgery before 50*. Osteoarthritis of the back, hips, etc runs in my family. The one preventative measure I have been able to find in my online research is losing weight or maintaining a healthy weight. Which I am endeavoring to do.

    Sure, It may not lengthen your lifespan, but less pain is always good in my book.

    *I will reassess goals at fifty.

  10. Obviously the issue is very complex. But that complexity does not justify the conclusion that adiposity itself is completely benign.

    The issue of sleep apnea is one example – this directly results from being overweight in many cases, and can be cured by losing weight. It is not only disruptive to quality of life, but is comorbid with many other problems, and is even a risk factor for heart attacks and strokes.

    So, yes, inactivity itself is a health problem that correlates with being overweight and therefore complicates the data on being overweight – but that does not equal overweight being a non-issue.

    I do agree that it may be more practical in many cases to focus the patient on getting regular exercise and improving their diet, and letting the weight take care of itself, rather than focusing on the weight. But that is a separate issue.

  11. BobbyG says:

    I work in the REC Meaningful Use program in Nevada. One of the core criteria for compliance is the capture of height and weight as numeric data which the EHR will then use to calculate and capture BMI for assessment and subsequent flowsheeting.

    We had one overwrought Reynolds Wrap Haberdashery citizen up in Reno cut & paste the section of the MU CFR Final Rule specifying the requirement of the EHR to calculate, re-display, and store BMI into an editorial comment in the paper. This PROVED to him that the the federal government would soon be dictating what we could and could not eat.

    Michelle Obama and her dreaded celery sticks, etc.

  12. LovleAnjel says:

    It’s nice to see this addressed in a science-based forum. It irritates me that the results from studies (like the one linked by Bacteriophile) get misused. My gym had a poster highlighting the study, but lumping the overweight and obese categories together and dropping the underweight category (which also has increased health risk), effectively stating that anything above normal weight was bad, and anything below was okay.

    This filters down to practitioners – I had a fasting glucose test that turned up 99. My doc told me that was perfectly fine, no worries. An overweight person goes in, gets a test with the same result and is told she is “pre-diabetic”. Excuse me? That means she doesn’t have diabetes (not even close – hitting 100 gets you hypoglycemia). So a person with a healthy test result was given a different story and different recommendations, solely based on her weight.

  13. Anthro says:

    It may not be proven that my significant (and maintained) weight loss will increase my life span, but it has certainly made the intervening years healthier and less dependent upon medical intervention.

    * No longer diabetic

    * Normal blood pressure

    * Reduced statin rx – used only to maintain extremely low levels due to family history.

    Plus, I look and feel a lot better in a size 6 than I did in a size 12 or 14, which has done wonders for my self-image.

    But how did you DO it, they all ask? EAT LESS–and stay with it.

  14. Great comments about weight and knee pain, weight and back pain, and weight and sleep problems.

    Totally reasonable.

    So: why don’t we see weight data on the study sample reported anytime we see a pain or sleep study?

  15. ConspicuousCarl says:

    I used to be one of those obesity deniers. After all, height vs weight is too simplistic because you could be a totally buff athlete and have the same BMI as a fat guy!

    I forget exactly when I heard someone point out that all you have to do is look out the window and see that 50% of the people on the street are not ultra-buff action heroes who are confounding the data with 50 extra pounds of muscle. They are, in fact, fat.

  16. Livingston in the Sept 6 Ann Int Med has a good comment on the limited clinical benefits of bariatric surgery: no life extension, plus fair or high risk of bad side effects in the long run.

  17. cloudskimmer says:

    Difficulty in finding size small when shopping for clothing is one of my data points in confirming that Americans are becoming increasingly large; even when something is labeled small, it is often larger than my memories of small used to be. Yes, I know that’s an anecdote.

    My question is: When does falling below some low point become dangerous to a person’s health? Back in the 1970’s and ’80’s, concern about girls with anorexia was a popular health topic. Even if it’s rare, shouldn’t there be some medical concern with people who are underweight? What BMI is considered too low? This is a real problem for some elderly people; it’s not unusual for them to fail to eat enough when in depressing circumstances such as nursing homes, assisted living facilities and hospitals, but it often goes unaddressed due to general neglect of the elderly and the cascade of other more urgent problems. Yet it is a real issue, and ought to be addressed.

  18. LovleAnjel says:

    @ cloudskimmer

    A BMI below 18 is considered underweight, and it does come with some health risks. It’s actually healthier to be in the overweight category.

    Oddly, the “curvy” Hollywood actresses held up as “Look! Not a stick! Just like you!” like Catherine Zeta-Jones & Jennifer Lopez have a BMI of 18. A “normal” actress is in the underweight category.

  19. Diomedes says:

    While I certainly believe that rates of overweight and obesity have increased, and that these have negative consequences for the health of individuals, I do get tired of the present hysteria over the “crisis.”

    I agree with other posters that the priority should be evaluating the diet of the patient and their activity level, and urging them to improve both, without carping on weight.

    If I’m not mistaken, once adults become obese, they are almost certain never to lose that weight permanently. If that’s true, why the hysteria? Why not just accept that once an individual is adult and obese, they’re effectively a “lost cause” and focus on improving their quality of life to the extent that it is possible? Let’s save the concern for the next generation and make changes in our neighborhoods and schools to prevent obesity in the young.

  20. Canucklehead says:

    I have to say as a physical therapist, mobilizing and activating heavier clients post op knee/hip/back etc surgery is much much harder both on them and me. I find I’m supporting more weight for them even though I use the correct methods and assistances. I shudder when an overweight client with a fresh dense stroke is booked for mobilization. I think the risk and injury to health care professionals who have to help move these overweight clients about, and get them moving themselves, is probably under reported.

  21. Skemono says:

    Thanks for posting on this issue–although I kinda wish you’d spent more time on the health risks of obesity rather than linking to one site. But the information about BMI corresponding to obesity was new to me.

    By the way, I think one of your links is wrong. The page linked to as “website advocating size acceptance we read” doesn’t contain the text you quote. I think you meant to link this page:

  22. Skemono says:

    Many health care providers and systems, and public health campaigns, alarm people that being overweight is the problem.

    It is not.

    Poor diet and inactivit are the problems. If a person is eating fairly well, and getting modest exercise regularly, they can be fat and happy without much worry (ignoring various exceptions such as thyroid disorder).

    While physical inactivity and diet certainly contribute to health problems, I don’t think that means that obesity itself does not also do so. Dr. Novella already mentioned sleep apnea, and there was a study on diabetes which found that:

    Obesity and physical inactivity independently contribute to the development of type 2 diabetes; however, the magnitude of risk contributed by obesity is much greater than that imparted by lack of physical activity.

  23. BillyJoe says:

    Ironically, Dr Novella himself falls into the overweight/obese category. But he has only himself to blame. After all I did offer to take him over the Dandenongs on my Sunday morning walks, and it’s not my fault he didn’t even do the courtesy of replying.

  24. Skemono: Yes, obesity is associated with, and probably has a causal role in, diabetes, as well as other medical problems.

    It makes sense to pay attn. but here is why I posted what I did:
    My view is from the population perspective, overall. If you are overweight, you are not necessarily going to get diabetes.

    The perspective in the post was from the perspective of the clinical population: given that a person has diabetes, is being overweight a predictor, and possible causal factor?

    Flegal (JAMA 2007) illustrates the idea that being obese does not doom you to diabetes, or diabetes-related death. This study slices and dices NHANES data in several ways, but it looks like (Table 4): for an obese person, the most likely leading doom is CVD, followed by cancer, then “non-CVD, non-cancer.”

    They lump kidney disease with diabetes in their Figure 3, so between Table 4 and Fig 3, we cannot quite see the excess mortality due to diabetes alongside that attributable to other causes.

    Not to say that an obese person should not worry about diabetes. My point is that being overweight or obese does not necessarily doom you to early death, and this worry is more distant if you are “fit fat,” i.e., exercising, eating decent diet, not smoking, and enjoying a glas or two of red wine each evening.

    Pischon 2008 NEJM has similar epidemiological data from Europe, but with even less break-out of diabetes.

    [An aside: the Flegal Fig 3 captures the phenomena noted above: there is a fair amt of early death where people end up with “normal” BMI as part of the illness process, making the”overweight” BMI group look very good relative to the “normal”-BMI group.]

  25. Scott says:

    It makes sense to pay attn. but here is why I posted what I did:
    My view is from the population perspective, overall. If you are overweight, you are not necessarily going to get diabetes.

    So what? If I shoot myself in the chest, I’m not necessarily going to die. That doesn’t mean that I can’t substantially reduce my risk of death by not shooting myself in the chest.

    The perspective in the post was from the perspective of the clinical population: given that a person has diabetes, is being overweight a predictor, and possible causal factor?

    I don’t think this is a correct characterization, or indeed even close. Rather, the operative question is “Given that a person is overweight, will it reduce their risk of diabetes (or other problems) to lose weight?”

    Not to say that an obese person should not worry about diabetes. My point is that being overweight or obese does not necessarily doom you to early death, and this worry is more distant if you are “fit fat,” i.e., exercising, eating decent diet, not smoking, and enjoying a glas or two of red wine each evening.

    Off-target. The question at hand is, again, whether an overweight person would benefit from losing weight. Of course it doesn’t “necessarily doom you” – we’re talking risks, not certainties.

    Whether being “fit fat” is better than “unfit fat” is a significantly different question than whether being “fit unfat” is better than being “fit fat.” Answering the one does not provide any particular insight into the other.

    More generally speaking, you appear to be taking the position “exercise, good diet, etc. are good for you therefore it doesn’t matter how much you weigh so long as you’re doing those things.” Which is not really a justifiable position. If you instead intend to imply “exercise, good diet, etc. are MORE IMPORTANT than how much you weigh and therefore warrant closer attention, but weight still needs to be considered” that’s reasonable. But you’re sure giving the impression that you feel weight should be ignored completely.

  26. Henchminion says:

    It’s not that I contest the data in this post. I just can’t help thinking that the context is very strange.

    When I walk into a bookstore, there’s an entire section dedicated to nutrition woo, promoting everything from hyperventilation for weight loss to a diet made up exclusively of yoghurt. The insane diet books outnumber the acupuncture books by at least 20 to one and their potential consequences are far more dangerous.

    There’s a major American TV show that begins episodes with the words “Nearly 100 million Americans suffer from debilitating obesity.” I understand that some health-care professionals are taking bets on how long it will be be before such reality shows manage to kill someone.

    But on the few occasions when Science-Based Medicine decides to take on this mountain of misinformation, Dr. Novella devotes not one, but two posts to carefully refuting the real enemy … an obscure political blogger. That’s courage, or something.

    How can this post possibly be seen as anything but a social, moral and political statement?

  27. BillyJoe says:


    I think you are missing the point.
    If the prevalence of diabetes can be halved by all obese people reducing their weight into the normal range, that’s a big saving in health costs to the community.
    However, if I am obese and I reduce my weight into the normal range, I might reduce my chances of getting diabetes by only five percent.
    Big community savings but not a sufficient reward for the individuals whose effort is required to get us there.

  28. BillyJoe “Big community savings but not a sufficient reward for the individuals whose effort is required to get us there”

    That’s a good point. I would expand on that and ask, If the community and or workplace wants the savings, is there anything they can do to decrease their populations risk of become obese? For communities, safe playgrounds, walking and biking paths, access to reasonably cost healthy foods, cooking and healthy diet education are a few things that come to mind. For workplaces that require sedatary work or shift work are there preventative measures that could be taken, such as decreased work hours (say 40hrs instead of 45 to 60 hours for salaried worker) altered workstations, on-site catering of lower calorie healthy foods (instead of the local fast food chains), on-site exercise rooms and showers, etc.

    Of course those thing would cost money. I guess the communities and workplaces have to decide whether it’s worth the investment.

  29. Mark P says:

    I dislike talk about the “fit fat”. A lovely idea, not met very often in reality.

    My experience is that there are people who start to put on weight and through their twenties and thirties are the so-called “fit fat”. And then they turn into the merely fat.

    If we allow the concept of “fit fat” we are in danger of allowing people overweight at thirty the idea that there are no future dangers: they can be obese and healthy. But then some injury or illness strikes and they lose mobility. And suddenly their weight is a major problem.

    “If I’m not mistaken, once adults become obese, they are almost certain never to lose that weight permanently. “

    This is, presumably, because they are incapable of dealing with the reason they are overweight (generally over-eating), rather than because their bodies won’t let them. There are plenty of people who lose significant amounts of weight once adult. Surgery that works merely by preventing over-eating is often very effective.

    I do find it amusing though that we are meant to be tolerant of the excessively obese. Yet we are encouraged to have very little tolerance for smokers, drug takers or people who drive drunk. Sorry, but I put over-eaters in the same category as those people. I know it’s very old-fashioned, but the concept of self-control is still valid.

  30. Mark P “Yet we are encouraged to have very little tolerance for smokers, drug takers or people who drive drunk”

    As someone with asthma, I dislike smoking because it screws up my breathing. Drunk and drug abusing drivers kill and disable people.

    I generally consider the risk that someone takes with their own life to be reasonably within their own domain, or at least between them and their children and loved ones.

    I’m always bemused by folks who don’t “tolerate” the overweight, obese, but do tolerate or admire high risk athletes such as rock, mountain climbers, race car drivers, extreme skiers, football players, boxers, etc.

  31. michaelSkiCoach says:

    I’m very concerned about the new notion that it is possible to be fit and fat. I coach teens and my kids vary from almost too skinny to quite plump. A few additional pounds do not prevent kids from being active and from being social. Being very overweight or obese certainly does.

    Parents need to be encouraged to help their children deal with unhealthy wieght and not be given an other excuse to simply ignore it.

  32. Toiletman says:

    Unfortunately, one aspect I wonder about was not mention.
    Does weight matter in terms of drug dosage?

  33. pedshosp says:

    To answer the question about definitions in kids, they have made some adjustments. Essentially, the current percentiles are based on populations that no longer, or never actually did, exist. For the CDC curves made in 2000, the weight percentiles for children over 6yo were only based on measurements from data up to 1980; later data were excluded. For the WHO curves made in 2006, data come from 6 countries, and data points over 2SDs higher than the mean were removed from the sample used to make the percentiles. Curious what the rates of overweight/obesity were in the US compared to the other 6 countries? Me too. The WHO won’t publish country-specific data.

    I enjoyed the post. I am saddened but not surprised by a few of the comments. I would imagine that all of the posters consider themselves advocates of, if not practitioners of, science based medicine. But some commenters seem to ignore large amounts of evidence that internal drives to maintain a particular body weight are incredibly strong and that weight status is in large part genetically determined. I understand that for many people this is considered an extraordinary claim that requires extraordinary evidence. If these people feel that the evidence is not currently sufficient to support the claim, then I would disagree, but would respect the fact that they at least considered the evidence.

    And for that reason, I strongly agree with the person said that discussions about the morality of being obese, and of discriminating against the obese, should generally be separate from discussions of the health effects.

  34. MarkHaub says:

    Great discourse…An issue this discussion truly hinges on is what is “healthy”, or how is it defined. If one carries more weight, yet has similar mental/physical clinical outcomes as a less heavy individuals, is their health different? Or, if an obese individuals engages in “healthy” behaviors (whatever those are) and decreases BMI from 46 to 41, are they healthier even though they did not change their obesity label? Is their depression, or increased risk of depression, still present with the presence of the ‘obese’ stigma? This latter issue pertains to the Public Health vs Individual dichotome as the “label” is meant for addressing public health issues, while the treatment/prescription is individual. Thus, one can be individually “successful”, yet remain unsuccessful at the population level — and what level do they hear/see repeated in media? That there’s a war against obese people, err…obesity. [edit – I have a difficult time containing sarcasm].

    Moreover, does it matter how one loses weight, if weight loss is important? I recall, about a year ago, a professor of nutrition using himself to hit on this point. Since weight and BMI are the focus of the #1 public health issue, he used foods deemed “unhealthy” to become “healthy”. While an academic exercise, it was an interesting means of addressing this weight vs health concept. It seemed as though everything that is recommended (less fat mass and weight; decreased LDL, TG, glucose, TC; increased HDL; less sleep apnea; and more “energy”) occurred with that junk food diet — yet most (all?) health professionals said he was unhealthy. Interestingly, that professor’s outcomes were amazingly similar to those reported on “Forks Over Knives”. Alas, one must be careful as the assessments were made during weight loss. The professor failed to report metabolic changes after he reached stability; or, maybe he knew what would happen…

    One must be careful when comparing weight loss to weighing less as Assali et al, (J Endocrinology, 2001) reported, the process of losing weight elicits the primary metabolic improvements. During weight maintenance, metabolic outcomes tend to creep back to pre-weight loss values — even when weighing less (seen in Brehm et al. 2003 when comparing pre and 6 month results). From a research design perspective, we really need to be cognizant of what state the variables are measured. Most newer studies use “run-in” diets to stabilize weight prior to the intervention and then re-test in the weight stable phase. When testing is done in the weigh stable (energy balance) phase, regardless of weight loss, metabolic and CVD benefits tend to be underwhelming if evident (e.g., L Joseph et al., Diabetes Care, 2001).

    Thanks to all those who chimed in, great comments and insight. Look forward to reading more.

    Cheers — Mark Haub, PhD

  35. MarkHaub sez:
    “Moreover, does it matter how one loses weight, if weight loss is important?”

    I wish this phrase would have occurred to me.

    If you have a very pale patient, you ought to be concerned whether they are getting enough exercise and/or natural sunlight.

    Both have grave health implications. Grave.

    The paleness is a clue. being pale, in and of itself, is not (usually) a disease. And getting skin tone lotion, spray-on tan, or eating a lot of carrots will not solve the problem, although the person will be less pale.

    If you see an overweight person, you should be concerned that they are eating a diet that is not high enough in fiber, and or that they are not exercising enough.

    In both the case of paleness and beign overweight, and to some degree being obese, the visually detectable clue is merely a clue.

    The proper intervention is NOT weight loss (analogous to spray-on tan).

    Great discussions.

  36. Toiletman asks if weight matters for drug dosage.

    Yes, sometimes.

    Some drugs are “lipophylic:” when they get to body fat, they like to stay there. Traditional antipsychotics are often lipophylic and this makes dosing in obese people challenging. I have seen incredible doses of depot-neuroleptic administration to really obese people – it is stunning because the TD side effects would usually be off-the-chart well before these high doses, but the injection goes into sub-cute fat and stays there.

    There is the belief that weight loss can cause liberation of chemicals, including heavy metals as well as antipsychotics, held in the body fat. I don’t know if this is supported by evidence.

  37. CarolynS says:

    The definitions of the terms overweight and obesity are pretty squishy. For about 12 years, the definition of overweight in the US was a BMI of 27.8 for men or 27.3 for women. There was no accepted or widely used definition of obesity at all, so the comment that it didn’t change isn’t correct. There really wasn’t one. The NHLBI change in definitions in 1998 was not really the result of any particular expert knowledge. Mostly it was to align the US with the WHO definitions (which themselves were arrived at with considerable financial and practical assistance from a group largely funded by drug companies). The change in definitions was described in the New York Times at the time as a present handed to the drug companies on a silver platter by the government. It did introduce the terms “overweight” and “obesity” as two levels of BMI.

    For children, several expert committees recommended use of the 95th percentile of an approprite reference population as the definition of overweight, and there was no definition for “obesity’ in terms of BMI for children. Between the 85th and 95th percentile was considered a kind of screening level indicating children who might be considered overweight but who should be investigated further. Several years ago, these terms were changed to “obesity” for whas was formerly “overweight” and to “overweight” for what was formely the screening level. There was no particular scientific reason for these changes except to accentuate the seriousness of the problem. No new information was used.

    These terminological changes do make things look worse and worse even if no other changes had occurred. Right now, things look pretty stable and overweight and obesity dont see to be increasing by much if at all.

  38. Sure, this discussion thread is now dead. But will I let that stop me?

    Am J Epi just came out with a study on BMI predicting to PAD: higher levels of BMI seems to indicate increased risk for PAD, unless it doesn’t, in cases where you are ill from PAD, and your weight is dropping due to illness.

    Does this support my pet theory (whatever it is)? I don’t know yet.

    But it is cool to see more subtle analyses emerge – something other than: your “BMI is 27 – you must lose weight.”

    Association of Body Mass Index With Peripheral Arterial Disease in Older Adults. The Cardiovascular Health Study Am. J. Epidemiol. (2011) 174 (9): 1036-1043.

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