Interesting article. I don't know that I'd take too much to heart given some of the obvious caveats the author has been nice enough to make explicit, but it sounds like I'd be hard pressed to argue the suggestions contained within.
For the tl;dr crowd:
- written by a physician
- people often think that heart disease is controllable by our actions whereas they feel that cancer is not
- > people can’t change many risk factors of heart disease like age, race and family genetics
- > A more recent study published in Nature argues that there is a lot we can do. [about cancer]
- > Using sophisticated modeling techniques, the researchers argued that less than 30 percent of the lifetime risk of getting cancer was because of intrinsic risk factors, or the “bad luck.”
- > [another study] identified four domains that are often noted to be related to disease prevention: smoking, drinking, obesity and exercise
- if you limit that stuff, and not meaning 0 smoking, but "having quit within the last 5 years", no more than 1 drink a day (women) or 2 drinks a day (men), your BMI is >= 18.5 and <= 27.5 (BMI is such a shit and antiquated metric, IMO, incidentally), and perform 150mins/wk moderate intensity excercise or 75mins/wk vigorous intensity exercise, then you're in the low risk group. so the barrier to entry is not super high.
HOWever:
> No study is perfect, and this is no exception. These cohorts are overwhelmingly white and consist of health professionals, who are not necessarily like the population at large. But the checks against the national data showed that if anything, these results might be underestimating how much cancer is preventable by healthy behaviors.
[...]
Optimistic conclusion, for a skeptical cheapskate like myself,
> As we talk about cancer “moonshots” that will most likely cost billions of dollars and might not achieve results, it’s worth considering that — as in many cases — prevention is not only the cheapest course, but also the most effective.
Hard to fault this article. I'm glad you posted it, thank you.
BMI is a tool for doctors to use, along with clinical judgement. No doctor is going to look at a lean, well muscled individual and tell them they're at risk for heart disease because their BMI is high.
BMI is something that fails in theory and works in practice.
I thought it was a tool for measuring large populations where the lean, well muscled outlier is heavily outnumbered/balanced out by their opposites. Either way though I agree that it's silly for individuals to try to apply it to themselves and then shit on the concept because it doesn't work like that.
That's correct. On a population basis BMI is useful, on an individual basis there's too much variation for it to be useful as more then a very loose guideline.
when you record someone's BMI and it gets thrown in a spreadsheet as patient 123456 has BMI 23.5 the doctor is no longer looking at the patient. perhaps it's good enough, i don't claim to be able to evaluate the methodology of the study (and perhaps using BMI simply results in more skeptical results, by leaving healthy people out of the low risk group, which I'm fine with - not sure this is true though). it really was an incidental note on my part, but i stand by it. i am a little surprised at how much we're talking about it, i guess it is bikeshedding, which is understandable, im not qualified to comment with authority on much of the material myself :)
What's wrong with BMI for something like this? It's such a simple measure and it seems to be useful for predicting health issues. From what I've read body fat percentage is what really matters, but accurately calculating that takes expensive equipment. http://www.nytimes.com/interactive/projects/cp/summer-of-sci... seems to indicate that BMI does a pretty good job, although it may be too generous on the high end.
> It's such a simple measure and it seems to be useful for predicting health issues.
It is good for predicting in general populations, but can easily fall apart with individuals. It doesn't take into account what the makeup of your mass is. Muscle is denser than fat, so a muscular man and a fat man of the same height and weight would have the same BMI, but vastly different health profiles.
>It is good for predicting in general populations, but can easily fall apart with individuals.
While it can "easily fall apart with individuals", the difficulty lies in finding an individual to measure that will make BMI fall apart.
And that's because the huge majority of us is of the kind of complexion and body type where BMI works well.
So, sure it can give false positives, but for a quite small fraction -- besides any other rough medical heuristic does the same (e.g. signs of having the flu can also be caused by 200 other reasons).
The "individual measure" you're looking for is body fat percentage.
A vastly more accurate proxy is waist circumference.
BMI was developed largely because the proxy data (height and weight) are so readily available, especially in databases. Few doctors take waist measurements, and doing so is slightly more complicated.
> the difficulty lies in finding an individual to
> measure that will make BMI fall apart
I'm 5'11 with a 36 inch waist. This gives me a waist-to-height ratio of 0.507, which has me just under or over the healthy cut-off, depending on who you ask[0].
I was 212lbs this morning, giving me a BMI of 29.6, which has me at the border of "Overweight" and "Obese Class I (Moderately obese)", and is high risk.
I don't think you'd think I was a weird shape if you looked at me.
I see how it is a bad measure for some cases, but I don't think that makes it a bad tool. It's like financial advice that says how much someone should save for retirement or spend on rent based on income. Someone with a normal job progression will probably be fine following it, but for doctors who take out huge loans and eventually have a huge increase in income it's not helpful and a more specific plan should be created. For BMI, most people should aim for the middle of the range and if they think there's a reason that they don't fit the scale then a doctor can be consulted.
Why do people keep bringing up this point. Even blood tests are not perfect tools but we still make use of them. There are always some false positives and negatives. It is a combination of all the available results that a doctor will use to make a determination. If your BMI is high but you look muscular, have normal BP and cholesterol and no other concerns, they may feel that you are in good health.
I think the sort of person to be incredibly muscular is probably also one of the most likely groups to get body fat measurements, and be educated about the limitations of BMI. Because that person is almost certainly a bodybuilder, serious athlete, etc.
The link you provided indicates that BMI is incorrect (when compared to body fat %) roughly 1 in 5 times. That's pretty high, IMHO and that is why many people have a problem with it.
Having known some weight lifters, they generally dislike BMI because they are typically considered 'obese' due to their unusually high weight in muscle, whether or not they are in good shape (typically they are).
Calipers are also $10 and measure body fat accurately enough for health purposes (body building may be an exception in this as well, but only in extreme cases).
>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.”
BMI is a surprisingly relevant metric for many things as it's a comparison between volume (weight) and surface area (height ^2). And yes, short people do have an inherent advantage there which for example possibly relates to how small dogs tend to live longer.
Because muscle and bone are denser than fat, and exist in higher proportion in fitter people, two people could easily have identical BMIs even though one is a powerlifter with 5% body fat and the other is mostly made of Cheetos.
Yes, but powerlifters with 5% body fat are far more rarer than Cheetos-munging fat people.
So the possibility of such false positives is not that high, making still a good heuristic. Not to mention: if one is a thin, mostly-muscle powerlifter type, they already know they are not obese...
BMI is a horrible metric because it doesn't take body composition into account. I can't believe I was once almost considered obese with a body fat of less than 5%. 5'10" at 200-210.
My BMI is 26+ and I run ~8 miles/day. It can be pretty far off for larger built people...
I clearly remember asking my gym teacher in middle school why my BMI suggests I was fat even though I clearly wasn't. He then proceeded to tell the entire class "he's a good example of someone who's labeled as fat, but isn't." Somewhat embarrassing.
My employer had one of those physical checkups for a lowered rate on insurance. I'm 5'10", 215 pounds[1]. The doctor sighed and said that he was required to tell me that according to BMI, I was obese and should consider losing weight. We had a good laugh about it.
My body-fat percentage is definitely not 5%, though. My guess is that it's around 14-15%. Everyone drastically underestimates how low their body-fat percentage is, and I am not a bodybuilder. I lift heavy and like pasta.
Your heart does not care if it's supporting fat or muscle it must pump blood for both. Further skin and colorectal cancer are both surface area and don't care about fat vs. mussel.
Metabolically muscle is worse as it needs more oxygen and fuel. Which is one of the reasons body builders can often die young from a heart attack.
Taller people tend to have larger hearts and wider artery's which makes a difference. It's pressure = flow rate / diameter of pipe ^ 2. So, as you gain weight your arteries can get wider or the pressure can increase.
Gaining weight increases skin, which is why skin reduction surgery happens for people that lose lot's of weight. GIS for skin folds.
Weight / height ^2 is a proxy for both it's far from perfect, but it's also really easy to collect.
It's not doctors who provide the most trouble, it's rules and regs coming from your health insurance or your job. There are plenty of stories about guys in the Army who can meet all their physical requirements but are getting dinged for having a BMI a smidge too high. Or if your job gives you a discount on health insurance for meeting certain standards, you may not qualify if your BMI is a bit high -- even if you're a champion athlete.
When I last went through a health screening with a qualified professional, I was congratulated on my great health and great cholesterol levels. However, on some online screening I had to do for health insurance around the same time, I was warned that my BMI is a smidge high and my cholesterol is 1 point higher than desired. The online screening did not take into account activity level, functional health, or the differences between HDL and LDL. When health or financing decisions are made algorithmically there are some real traps.
For the tl;dr crowd:
- written by a physician
- people often think that heart disease is controllable by our actions whereas they feel that cancer is not
- > people can’t change many risk factors of heart disease like age, race and family genetics
- > A more recent study published in Nature argues that there is a lot we can do. [about cancer]
- > Using sophisticated modeling techniques, the researchers argued that less than 30 percent of the lifetime risk of getting cancer was because of intrinsic risk factors, or the “bad luck.”
- > [another study] identified four domains that are often noted to be related to disease prevention: smoking, drinking, obesity and exercise
- if you limit that stuff, and not meaning 0 smoking, but "having quit within the last 5 years", no more than 1 drink a day (women) or 2 drinks a day (men), your BMI is >= 18.5 and <= 27.5 (BMI is such a shit and antiquated metric, IMO, incidentally), and perform 150mins/wk moderate intensity excercise or 75mins/wk vigorous intensity exercise, then you're in the low risk group. so the barrier to entry is not super high.
HOWever:
> No study is perfect, and this is no exception. These cohorts are overwhelmingly white and consist of health professionals, who are not necessarily like the population at large. But the checks against the national data showed that if anything, these results might be underestimating how much cancer is preventable by healthy behaviors.
[...]
Optimistic conclusion, for a skeptical cheapskate like myself,
> As we talk about cancer “moonshots” that will most likely cost billions of dollars and might not achieve results, it’s worth considering that — as in many cases — prevention is not only the cheapest course, but also the most effective.
Hard to fault this article. I'm glad you posted it, thank you.