Body mass vs. body fat: How often is BMI misleading?

[Ego]

Adding to what Jacob said....

Being unhealthy is contagious because people who are failing at something tend to subtly undermine those who are trying to be successful. Misery loves company.

Be aware. Pay attention. Some people, when they find out you are trying to get fit, will bring a six-pack, chips and cheese-whiz the next time they visit. Others will go out of their way to help you succeed. Some places will cause you to revert to bad habits. Others places will encourage and reinforce positive changes. Notice the people and places that do each.

Some people can easily be eliminated outright from life. Some can't. Some can be retrained. Some can't. Some environments are just so toxic that they have to be completely avoided. Unfortunately some of those toxic places can't be avoided.

Minimizing the impact of the 'can't avoid' people and places is one of the hardest parts of making healthy changes.

[Scott 2]

In my experience, lasting change requires becoming a different person. Anyone that will powers their way into a new weight reverts back to the old one, once life happens. The reversion happens startlingly fast.

A person has to find a way of eating that makes life easier or better. They need an active hobby that kindles passion, offers a social outlet, and is physically sustainable. Everyone else changes back over time.

I also don't think there's anything wrong with accepting that the person you are means you'll be happiest leading a life that results in a high BMI. The trade offs are clear, if they're worth it, so be it. Enjoy the life that fits you best as a person, and feel good about recognizing it.

[7Wannabe5]

I think Jacob's division of men into the formerly athletic vs. not group is revealing, but not exactly for the reasons he noted. Active testosterone levels are well known to decline quite steeply with age and are also strongly negatively correlated with obesity, high blood pressure and grouchiness and positively correlated with ability to add and maintain musculature and also sexual function. It's not just that the men who were more athletic in their youth still retain the habits; it's also that they still retain relatively higher (or, perhaps, more useful) hormonal levels and, therefore, are more readily able to put on muscle and get back into shape. Of course, it is true that all sorts of behaviors, including regular exercise that tends to add muscle and taking on positions of leadership/mastery, do tend to raise testosterone levels. Taking testosterone generally alters mood towards bright assertiveness and engaging in any activity that lends itself towards making you feel bright and assertive will also naturally raise testosterone. This is the underlying reason why both ingesting coffee and participating in sports were at one time considered to be unladylike.

IOW, I think BMI, although statistically valid, is not the best metric once you get down to considering the situation of any given individual. The particular hormonal influence of excess abdominal fat is likely to either be mediated or exaggerated by the individual's baseline hormonal profile, and the mechanisms of how declining hormonal levels are both sign and signal that we are of no further reproductive use and it would be best for the species if we just faded away into compost are not yet well understood. Therefore, being overly judgmental about the habits of others, rather than simply curious in our observation of correlations, may tend towards a certain level of blindness is recognizing that there very well may be a good deal of "luck of the draw" going on here (so damn unfair that the jerk high school football star may also be naturally more heart healthy and better able to achieve an erection at age 60!) from which we could learn and make better decisions.

[jacob]

@7wb5 - See the Fast After 50 book I posted in the Exercise Log thread.



Not everybody has the same genetics/nature, but behavior/nurture easily overrides(*) genetics. With age, to keep overriding genetics, behavioral responses have to become increasingly more consistent, intense, correct, ... etc. IOW, young folks can screw up their training, skirt injuries, eat junk food and still do well. Old folks can not.

(*) Overriding genetics is actually the wrong way to phrase it. Maximizing one's genetic potential is better. Genetic potential declines with age but for any age (except perhaps the last few years), the range of potential is so large that a given person at age 60 if making it a high priority can be in better shape than the same person was at age 30 if being in shape at that time had no priority.

Hence, as long as you're not comparing outliers, shape is very much more indicative of personal habits than personal genetics.

[Chad]

Those testosterone measurements are probably from sedentary people. Much easier to do a study with "normal" people than try and track down athletes in every age group. I bet the decline wouldn't be as steep for someone who consistently worked out and pushed themselves in those workouts. Something similar to this was identified with this study:

http://www.sciencedaily.com/releases/20 ... 121129.htm

...found that serum (blood) testosterone levels did not decline with increasing age in older men who reported being in excellent health with no symptoms to complain of.

[jacob]

Those testosterone measurements are probably from sedentary people.

They are. Also, they're probably from current people.

The fact that "normal people" now equals "sedentary people" also creates a skewed perspective on what's supposed to happen. Add the observation that average US adult weight has increased by ~25 lbs since 1960 making "slender" a minority and overweight normal. while this hasn't happened in other countries suggests that the behavior is neither genetic (too short a time span) or hormonal/environmental (effects are not global) but has to do with food and behavior.

[7Wannabe5]

Okay, here's the question. Let's say you have 4 different men who are all 52 years old and 6 ft. tall, as follows:

1) BMI 26. Rock hard musculature.
2) BMI 26. Moderately buff.
3) BMI 24. Soft appearance.
4) BMI 24 Moderately buff.

Would my female intuition likely be correct in determining their relative "shape?" IOW, given that the statement "shape is very much more indicative of personal habits than personal genetics" is true, is my feminine intuition running a merit-based program? Unfortunately, I am inclined to believe that this is, at best, only maybe 50% the case.

Also, I dated a man who was a serious jock in his youth and into middle-age. Somewhere on the internet there is a video of a one-on-one basketball challenge he won when he was 55. When he got into his 60s, despite his continued activity, healthy eating habits (would usually feed me something like a giant plate of roasted asparagus from his garden, organic turkey burger with no bun, glass of wine) and general rule of thumb of following all advice offered by Berkeley Public Health Newsletter , he started relatively (he was standard football player size) feeling like, in his own words, " a dry leaf about to blow away" , so he started supplementing testosterone and it worked very well.

Compare the chart below with the one Jacob posted showing testosterone decline. I have asked quite a few older men in my acquaintance, exhibiting varying levels of fitness, to compare their personal preferred sexual frequency (desire to ejaculate) at age 20 to age 50, and they have almost universally reported it to be right around half. Just because hormonal decline comes on at a slow creep for men vs. the rather rapid fall at midlife women experience, doesn't meant that it doesn't happen or that it can be totally compensated for through healthy natural practices. Nature wants us to eventually die.

http://www.sexarchive.info/ECE1/older_men.html

[banker22]

Those testosterone measurements are probably from sedentary people. Much easier to do a study with "normal" people than try and track down athletes in every age group. I bet the decline wouldn't be as steep for someone who consistently worked out and pushed themselves in those workouts. Something similar to this was identified with this study:

http://www.sciencedaily.com/releases/20 ... 121129.htm

...found that serum (blood) testosterone levels did not decline with increasing age in older men who reported being in excellent health with no symptoms to complain of.

Correlation / causation ? Those people with symptoms of high test levels... had high test.

[jacob]

Step 1: Check BMI. Alternatively, go straight to step 2.
Step 2: If BMI over 25, compare to picture below.



What's obese/unhealthy? Women over 31%. Men over 25%.

http://www.webmd.com/diet/body-fat-measurement?page=2

Much more info here:
http://www.builtlean.com/2012/09/24/bod ... men-women/

[7Wannabe5]

Interesting. I found the photographs on the second link most helpful. I look most like the 30% fat photo, and for a variety of reasons, at the age of 50, I have pretty much zero motivation to look more like any of the lower body fat percentage photos, but I wouldn't want to look more like the 35% body fat photo either.

What I would describe as "rock hard musculature" in a man who was 52 years old would be somebody who looks like the 15% body fat photo but with much more serious shoulders and guns (more like the first guy, but without the icky veins), so the weight of his upper body might take him slightly above healthy BMI. What I would describe as "soft appearance" would be somebody who has a belly somewhere between the 25% and 30% photo, but with much skinnier, rather flaccid arms and legs, so his weight would maybe be somewhat below healthy BMI level. Therefore, if body fat percentage is a more accurate health metric than BMI, I guess my feminine intuition is quite functional and I have no need to carry calipers.

[jacob]

Body fat percentage is very reliable (the measurement of it, only somewhat so though). Only thing that can screw it up (in terms of pictures) is that it matters where that fat sits (belly). BMI is only useful because it's very hard to fake and/or put a euphemistic spin on it. E.g. it's easy to suck the gut in when taking a waist-hip measurements. It's not so easy to be 2" taller or 10 pounds lighter on a scale.

Also "mirror-opinions" can be skewed if the relative comparison to "normal" has drifted because it has become normal to be unhealthy because only 1/3 of Americans actually have a healthy weight/shape at this point in time (2015 ... not 1950). Worse, they're a bit harder to estimate. For example, all the the men in the second link except the 40% guy were pretty muscular under the flab. This is not representative of the normal sedentary population.

FWIW - these days, I agree with Scott 2's position. If the happiness created by eating food exceeds the downsides and a deliberate choice is made, go for it. (I wasn't always this way. My younger self was a total ass about these things. My present self is more of a moderate ass ... actually I'm more low-key in IRL than I am on the forum/blog when it comes to wording opinions---anyone who's listened to the podcasts I've been in might get the jist).

However, unlike those who deliberately choose to smoke tobacco (I used to be quite the "fascist" about this too being completely unable to recognize anyone who might prefer the joy of smoking over the risk [of death] spectrum; but not anymore ... I reckon that for some the joy of smoking may exceed losing X years of lifespan), I think that when it comes to food (as well as many other issues), most are still in denial. They'll hide facts from themselves ("I'm pleasantly plumb/curvy/buff/strong"). They'll hide facts from others (secret stash of cookies). They will, like Ego said, subtly try to sabotage people who are trying to act "according to medical science" to get healthier ("have a cookie".)

[7Wannabe5]

AGE: 50

Height : 5' 8.5 "

BMI : 26.2

WHR : .72

Body Fat Percentage : 30 ?

BP : 116/70

Resting Pulse : 58

Blood Glucose/Cholesterol : Healthy

# Chin-Ups : 0

Exercise Program : 1 hour moderate/ 5-6 days/wk

Level of Organic Vegetable Consumption : High

Level of Polish Bakery Cake Consumption : Moderate/High

Price of Dress: $9.99 on the clearance rack

Likelihood of Getting "Free" Dinner or Sailing Lessons this Weekend : High/Moderate

[JL13]

@Wannabe

Agreed, the lowering of the bar makes it that much easier to be above average. It's a 1 foot hurdle nowadays.

I think BMI can be quite misleading. Considering for myself, my weight has stayed around 150lbs and my BF% has been between 10% and 20%. So my BMI stayed the same at 22.1. 150 lbs looks small at either end, body-volume wise, but man...did my face look different in photos. And there's nearly a 4" difference in pants waist size also. All this while BMI didn't change. A 22.1 BMI may sound healthy, but let me tell you, at 20% body fat no one was paying me any romantic attention.

Agree with Jacob though, BMI is not relevant for someone like me, it's relevant for 50% of the population that need a simple RED FLAG.

My father, for example, who has been seriously overweight his entire life, recently bragged to me than due to his new habit of choosing healthy fast food options (oxymoron?) he has gotten his weight down to a 'svelte' 220lbs. He considered this healthy. I pointed him towards the BMI table, and showed him how he's just barely now beneath "Obesity" and still deep in "Overweight".

[7Wannabe5]

@Jl13

Individuals have such wildly varying phenotypes, I guess it's really hard to come up with a one size fits all metric. I'm lucky because I basically have a flat stomach at 175 lbs. because I am tall to begin with and my torso is 4 inches longer than it should be relative to my stubby little legs. Lowering my BMI at my age would offer very little improvement to my romantic life, given that I am smart enough to let the men who prefer my type do the chasing. At around 165 my collar-bone starts popping out, and I want to keep the padding and estrogen storage on my hips. OTOH, like you, I am somewhat motivated to trade maybe around 10 lbs. of fat for muscle if possible, so I really should expand my strength training a bit beyond the level of my water aerobics class.

I just realized something kind of funny. Jacob indicated that from his perspective, the men in the body fat percentage photos had better than average musculature, whereas I was thinking just the opposite. Then I was like -Duh, that is because you state right at the beginning of your dating profile that biceps are one of the 3 things you are looking for in a man. So, whenever I am checking out a man on a coffee date, I am looking at somebody who has already self-selected/filtered for biceps and mostly all I have to do is determine whether the paunch is relatively too big. So my sample is highly skewed.

[JL13]

Those photos don't work for me, either. I have a 34" chest and I keep ALL of my fat in my belly. So at 10% BF I look like the 15% photo.

[Lemon]

@Jacob

You need to be really careful with 'mirror opinions' when dealing with the public. They tend to be that way for the reasons you mentioned: http://www.jneb.org/article/S1499-4046( ... 9/abstract People do not know what is healthy anymore.

One group I see that seem fall into that are men who go to the gym every so often but then have terrible diets. They overestimate muscle and underestimate fat in a big way.

In terms of individual choice. People really do prefer these things and live in denial. But then when a lunch that consists of a white bread sandwich filled with mayo, come crisps and a piece of fruit is the health option (it has fruit!) it is just so easy for people to be in denial.

Comparing to past photos probably works better in a better than before/worse than before sort of way. The actual number being largely irrelevant.

[7Wannabe5]

The reason why the waist to height ratio is a much better metric than BMI is that if you multiply it by a constant, it is equal to the ratio of the measure of your volume if you were shaped exactly like a sphere with the circumference of your waist, over the measure of your volume if you were shaped like a column with your waist as circumference with your height as height. Therefore, it is directly reflective of relative spherical-ness with no need to account for much higher density of bone tissue and moderately higher density of blood and muscle tissue relative to fat, as is the case if weight is one factor in metric.

I rest my case, but will admit that my self-interested motivation in promoting this campaign to change the metric is directly reflective of my preference for the physique exhibited by the over 40 year old man who rows vs. the over 40 year old man who runs.

[JL13]

@Wannabe

Don't you think you need to multiply by weight to make this an appropriate metric? Waist and height doesn't seem like it would have any indication of upper body size/strength. A 6' runner and a 6' bobybuilder may both have a 31" waist but have very different shapes (and would weight different amounts).

[7Wannabe5]

@J_L13

I think somebody who is 6 ft. tall with a 30 inch waist is just as healthy whether they run, row, lift or belly dance. I just don't want there to be any level of irrational encouragement towards overall skinniness since central body fat is the real issue. Unfortunately, nobody has yet made me the Queen of the Universe, so...(sigh)

[theanimal]

Where are you on the Global Fat Scale?

A BMI comparison among countries across the world.

I'm most like someone from Mali. The sad thing is that it says that I have a lower BMI than 91% of the males in my age group in the US. Wow.