Quiz Answers: Traits Associated With BMI

Last week we quizzed our readers on traits associated with BMI among 23andMe’s customers. Congratulations to Suellen, the winner of the quiz! She got all three answers correct and will receive an Amazon gift card. So what were the correct answers? Read on…

Which physical trait is most associated with BMI? Shoe size.

Shoe size is very strongly correlated with BMI in 23andMe’s database. For each standard deviation increase in shoe size, BMI increases by 1.18 units. Put another way, the BMI of the bottom fifth of the shoe size distribution is 3.21 units lower on average than that of the top fifth. This corresponds to a difference of about 20 lbs in people who are 5’8” tall.

We’re really not sure what to make out of this one. Shoe size is also correlated with height but when we factored height into the analysis shoe size was still the most strongly correlated trait. Anecdotally, people’s shoe sizes can increase or decrease with weight gain and loss. It’s possible that people with wider feet may compensate by increasing their shoe size instead of choosing a wider shoe of the same size, or perhaps shoe size is a proxy for body frame, and people with larger shoe sizes have “bigger bones”. Have a theory? Add it to the comments below.

Having a round face, low arches, upturned nose, and feet that point outwards are also associated with BMI but to a lesser extent.

Which food item is most associated with BMI? Diet soda.

The surprise for us here was that ice cream consumption was not really correlated with BMI at all. On the other hand, people who drink diet soda five or more times a day have an average BMI nearly 5 units higher than those who never drink diet soda. Not to imply that we should all trade in that diet coke for a double hot fudge sundae — we don’t know whether drinking soda is a cause, a consequence, or just linked to something else that causes weight gain. These findings do, however, parallel that of a study conducted in Texas, in which normal weight individuals were followed for 8 years. People who reported drinking more diet soda gained more weight over those 8 years, suggesting that diet soda might actually lead more directly to weight gain.(1) But for now, the jury’s still out.

Some other foods were associated with BMI, too, including red meat, yogurt, and vegetables.

Which personality or behavior trait is most associated with BMI? Activity and depression.

These are less of a surprise. Activity is strongly correlated with BMI, and is no doubt due to the calorie burning benefits of exercise. The reverse may also be true — being overweight may itself decrease activity levels, creating a vicious cycle.

For depression, the arrow of causation seems to point in both directions. For example, a recent meta-analysis found that being overweight or obese increased the risk of developing depression, and having depression increased the risk of becoming obese.(2)

Having greater levels of self-discipline was correlated with lower BMI to a lesser extent, but aside from this we didn’t find a significant relationship between BMI and any other personality factors.

Check back soon for our next quiz and another chance to win!

(1) Fowler, SP, Williams, K, Resendez, RG, Hunt, KJ, Hazuda, HP, & Stern, MP. (2008). Fueling the Obesity Epidemic? Artificially Sweetened Beverage Use and Long-term Weight Gain. Epidemiology, 16(8): 1894-1900.

(2) Luppino, FS, de Wit, LM, Bouvy, PF, Stijnen, T, Cuijpers, P, Penninx, BWJH, Zitman, FG (2010). Overweight, Obesity, and Depression: A systematic review and meta-analysis of longitudinal studies. Arch Gen Psychiatry. 2010;67(3):220-229.


  • Ploney

    Perhaps those people participating in the survey with higher BMI than avg. try to lose weight by consuming diet soda.

  • Lea

    Re: Shoe Size

    I chose that one solely based on my personal experience. I’m 5’5″, 172 lbs, size 12 pants, with a shoe size of 9.5-10 (I have been 145lbs with the same shoe size). Yet the circumference of my wrist is the same as the wrist of my husband’s who is 6’1″, 200 lbs, 10.5 men’s shoe, 32″x32″ pant. So right now my guess is that my shoe size correlates with my bigger bone structure, which in turn puts a couple more pounds on the scale. When I was 145lbs & size 9 I was quite thin with a somewhat concave stomach. That’s not a body image one usually imagines for a short woman at 145 lbs.

    This is all just anecdotal, but it was interesting seeing that shoe size does somehow play a factor. Thanks.

  • shari mackay toledo

    shoe size? my size increased due to pregnancy. i drink diet soda because its more refreshing, not because i need to lose a few pounds.

  • Flupke

    Would be nice to have international measure units. This is hardly understandable for a non US reader when it comes to weight and size.

  • http://Information.Architecture.Abacurial.com tOM Trottier

    re: “Some other foods were associated with BMI, too, including red meat, yogurt, and vegetables.”

    Looking at the picture, yogurt and veggies are associated with LOWER BMI, not higher.

  • Carolyn Scott

    I read a book that said diet soda (artificial sweetner) supports the growth of intestinal bacteria that favors or is associated with obesity, as opposed to the normal bacterial flora found in people of normal weight.

  • Joseph

    The Bigger foot= higher BMi actually makes sense to me. I was in the military for about 6 years and a large part of my job required travelling on foot with very heavy loads( 45 to 75lbs) in my rucksack. Im 5’7, 140 lbs, and my weight never fluctuated much in the past 10 years ( give or take 7 pounds) However, my feet grew from a size 8 to a size 9.5 and my feet became noticeably wider! Who knows why but its fun to think about.

  • Helena

    In german we know the expression: “auf grossem Fuss leben” (living on a big foot), which means kind of: consuming a lot, spending a lot of money. Turn of speeches often comes from an general experience and expresses a true thing in some way.

  • Julia

    I have never been overweight (except for my pregnancies, gained more 75lbs each time and my shoes size became 10.)
    I’m 5’7″ and I do have larger than most people hands, feet and head. “one size” never fits. However I do look proportional and everything seems in harmony. I’m considered to be objectively beautiful.
    My 9.5 shoe size probably inherited from my 6’7″ father whose shoe size was 13-14.
    My father was never fat or heavy. Your shoe size might grow as you gain more weight but I do not see the reverse relationship, i.e. if having big feet means you are prone to gain weight or that your BMI is too high.

  • Jarrod

    My gut feeling, tells me there is a scale issue related to BMI and foot size.
    As a person gets taller there overall body volume and capacity for that volume to increase is also larger, if the myriad of internal issues, ie, nutirient, hormonal, behaviour etc place a person in a situation that inturn raises there BMI, then there capacity for increases volume mill scale higher, i.e at 5′ 200lbs you look fat, at 6′ and 200lbs you look less fat generally, and it is also more indicative that a person of 5′ is going to have a smaller foot size then a person of 6′, alo note that the arch angle as it increases reduces foot length when measured big toe to heal.

    I think the leg/hip geometry, is more important, in proportian to torso length, and the old modality of overwieght, obease, and morbidlly obease, is not taking into consideration, how a person wears there weight.

    some people look bowleged and pronate, from there weight, also i higher proportion of inner thigh volume will cause the walking gait to be out of alignment, all this effects, growing and the size of the feet, a persons foot can change more then 1″ depending on the state of their arch, if an arch rises to compensate for bad foot leg geometry, due to increases in outer foot pressure, then a person foot may decrease in size, the opposite is true as well, a persons arch might collapse over time increasing there foot length. as these are not indicative of obeasity, rather then a partial end product, it is bad science to try to corallate these.

    People try the high level observation in science way to often, and the far majority, miss one very important part of high level observation (the approach order) one has to understand the chain of event first, and in living systems, this is very difficult, due to feedback loops, conditional reversals in systems etc.

    So Feet will never indicate the likleyhood of obeasity, because its to far down the chain for it to infleunce the upper chain. there is also the fact that in sprinters there is a large feet length vairence, and in marathoners this is also true regardless of above or below averages for each of the sports.

    in short, non scientific measurement of peoples overall skeltal dimensions (i.e survey) will never show a strong multi variate link.

  • Frances

    What is BMI?

    • http://abnormaldiversity.blogspot.com Ettina

      Body mass index – a measure of how fat you are.

  • Leonard

    About one known correlation between obesity and depression: Fluoxetine (prozac) is used in depression and obsessive-compulsive disorders like binge-eating or bulimia nervosa. In its mechanism of action, fluoxetine acts on the serotonine pathway in the brain (fluoxetine is a serotonin reuptake inhibitor). Serotonine is a kind of gauge of food availability (appetite) and a mood regulator.

  • Leonard

    Note: ny previous comment on obesity and depression was strongly inspired by wikipedia articles.

  • D Lee

    Hi Tom Trottier,

    You are right, correlation can be in either of two directions, positive or negative, and can be relatively strong or week in either direction:

    http://www.nvcc.edu/home/elanthier/methods/correlation.htm#Direction

    I think what the visual is trying to get across is that diet soda has a relatively strong positive correlation with BMI, while the correlation between BMI and, for instance, yogurt, is in the other direction (negative) and also is not as strong. Ice cream appears to be just barely positive, but the difference between that and no correlation at all is either not statistically significant or, if it is, the difference is so small as not to be thought meaningful.

    DL

  • http://Worthington-Levy.com CarolTheArtist

    @Frances:BMI is body mass index. it’s based on height and weight. Here is a good link -http://www.nhlbisupport.com/bmi/

  • Michael Hinsley

    Except for middle age where I gained 20 or 30 pounds, as an adult I’ve pretty much stayed around, 185 lbs, 6 ft. 4 inches. 13plus narrow, shoes, but in the last decade, gone up closer to size 15 medium shoe.

  • Noemi

    Shoe size increased each time after my three pregnancies, as well as my BMI.

  • Sara

    I’m 5’5 and I wear a size 9 shoe. Sometimes 9.5. I’m also quite thin. My feet are not wide though…just long…and flat. I’m small boned too. My foot size just doesn’t really go with the rest of me, but I’m thankful for it bc I also have long fingers, and it makes playing piano much easier! I think big feet usually correlate with bigger bone structure though, and in that way this “finding” would make sense.

  • Judy

    Since feet are part of the body, when one gains weight, the feet do too. If one is overweight for many years the feet would grow larger than they would if overweight for a shorter period of time. Flat feet are are often caused by the skeleton being under pressure for a long period of time. (Think of the PSI on the feet of an obese person!)

    I believe all of the other traits of an obese person start with the skeletal frame one is born with, and it being able to “normally” support only a certain weight. The excess BMI pulls on the skeleton over time and changes it. A turned up nose is because excess facial fat pushes around the nose and makes it appear to be naturally turned up, and because of the way the flesh connects to the bone around it. This also gives the face it’s shape. (Although I have an obese friend whose face is long.) I think these traits exist and are created BECAUSE of the increased BMI, and not the other way around.

    I started drinking diet soda because of Type II Diabetes, but also justified other calorie intake by saying to myself that much of my food’s calories would be offset by the diet drink, not knowing that the diet was causing any weight gain. Fortunately now I average less than 2-4 per week.

  • Will

    This one is simple. Imagine a short person and a tall person with the same BMI. We know that their height to weight ratios is identical, and so their diameter must also be similar. Of course, we know that a 4′ 6″ woman and and a 6′ 4″ man don’t have the same waist size. Nor, shoe size. The point is that the math behind BMI is way too simple to be independent of height. Taller people typically have higher BMI and larger feet; shorter people typically have lower BMI and smaller feet. It really is that simple.

  • payne

    will got this wrong; people with the ame bmi have different height to weight ratios, because bmi is ratio weight to heightsquared.!
    However the diameter will be in proportion to height, roughly, and this latter relation may turn out to be more important than BMI (as found in recent research.)

  • Ann L’Italien

    BMI itself is a faulty means of determining appropriate weight – it was designed to be a quick way to evaluate the results of a specific study. BMI does not have any way to account for muscle mass or bone structure. SOOOOOoooo, I would suspect any results obtained from this particular study. My lean muscular son appears obese if you use BMI.

    That said, I do notice that my shoe size will change somewhat as I gain or lose weight (which I have done frequently throughout my life) and activity definitely has a positive effect on my mood. Re shoe size: the ligaments of the feet do stretch and relax (my once very high arches are now just about normal). I would also expect fat deposition on the feet like you see in the hands (ring size anyone?).

  • Denis

    Honestly, BMI is not always a great measure. I.e. an athlete or just someone doing weight training may be low on body fat and have higher muscle mass than a regular person doing nothing. Their BMI may indicate that they are obese. It’s much better to have an estimate of body fat to make proper conclusions.
    Soda seems to be an interesting but it is probably correlating to other factos (i.e. lifestyle and diet), which consequentially lead to issues with BMI.
    Shoe size is rather interesting. Proportional scaling makes sense. But anatomical differences often influence the body composition. I.e. someone has bigger quads or pecs, while other parts are average or even below average.
    At 6.1 my shoe size is about 11.5 (and I have thicker bones around my feet) but my wrist is about 7 inches, so my hands/arms look much “skinnier” than the legs. too many factors seem to be involved.

  • Charlotte

    My podiatrist explained to me that most people’s feet enlarge as they age due to weakening of tendons and ligaments there. . . feet, as we age, spread out. As to the relationship of weight fluctuations and foot size, I can only report my personal experience. When I had an overweight BMI, I wore a size 40, (European measure) shoe. Since having a normal BMI for the past 3 years, my shoe size is now a 39.

  • Whitney

    When I gained weight, I also went up a shoe size, from 6.5 to a 7.5. After I lost the weight, my shoe size went back to 6.5. I never would have thought that weight gain and loss would affect shoe size, but it makes sense.

    As for the diet soda, I know that there are studies claiming that consumption of artificial sweeteners can serve as a trigger for people, making them crave “real” sugar and therefore possibly causing unhealthy eating. I’ve personally never had much of a sweet tooth, and I don’t have an issue with diet soda or other artificial sweeteners causing cravings, but everyone is different. Also, like another commenter mentioned, the correlation between diet soda consumption and a high BMI could be that some people are drinking diet drinks to attempt to lose weight (or not gain any more).

  • Ron Bartlett

    BMI for seniors should somehow take into account the fact that most of us have shrunk in height due to the natural degenerative process and that we still may carry the same amount of fat, lean muscle and bone mass. At 70, I am almost 1-1/2 inches shorter than in my youth and that difference is all between the top of my shoulders and my waist. That’s why my grandkids ask me why I wear my belt up so high!!!

  • http://www.garmaonhealth.com Joe

    BMI causes me some consternation.

    The measurement is practically worthless as I show in some detail in a post called “Just “Exactly” How Fat Are You Anyway?” http://wp.me/pA04z-10f

    Children, people very tall or short and anyone whose lifestyle (exercise, manual labor) builds more than average muscle.

    As I demonstrate in the above link, although I’m fairly lean and muscular, at 6’4″ and 212 lbs, am considered overweight.

    There are other equations than BMI that tries to account for frame size and muscle which I explore in http://wp.me/pA04z-10f

    Hope the info is useful.

    -Joe

  • http://www.garmaonhealth.com Joe

    Whoops… didn’t finish the second sentence in my last comment…

    Children, and people with various attributes (like muscle) will not get accurate BMI readings relative to it’s designation of “overweight”.

  • http://KSObserver Phil Coleman

    Well, there are always exceptions to the rule. I’m a 5’6″ male, BMI 30 (obese). My shoe size is 6-1/2 or 7. A shoe manufacturer told me there are more men needing size 18 shoes than size 7.

  • marty

    lea,
    5’5″ is not short in any stretch of the imagination! the average women in the u.s. is 5’4″. i am also 5’5″ and right now weigh 118, i do not look sick as a mater of fact i look good and feel good, mi shoe size is 7.5 and when my wieght has headed north i went into an 8. which was shocking as i have always been around 110. my shoe size never changed.
    since i’ve been through so many genetic tests over the yrs for heart problems i carry, i know that at my height i shouldn’t weigh over 130. i carry the KIF6 gene that increased my chances of have a heart attack by about 55%, i also have the APOE4 that increased even more, so my 2 – 30+yr old daughters that weigh around what you weigh are playing with a heart attack and stroke. this isn’t something i just found out, these are genes i learned about several yrs ago and have done much research believe me 23andme is another addition to all the genetic testing and research i’ve done, so don’t lull yourself into thinking that at the weight you are that your fine, it takes more than cholesterol testing to tell if one has the many heart stopper genes. ask berkley heart lab, get on their web site and ask them, someone will talk to you and explain their testing and why it’s so important to know what you carry.

  • Jeanne

    My shoe size changes slightly (about 1/2 size) when I gain or lose weight, and it’s not the width that changes. I assume it’s a combination of fat and water retention.

  • John

    It almost logically follows that a person’s feet may grow to support a heavier structure.

    I agree with others that BMI is a poor measure of actual body mass/composition.

    And contrary to Conventional Wisdom, sugar, artificial sweeteners, grains, legumes, and starchy vegetables contribute to weight gain.

  • Tina

    @Judy

    I disagree with the upturned nose thing. I think it may be something else genetically correlated with the propensity to become obese or something related to activity. I am clinically obese and amusingly I have most of the above traits (except large feet–mine are average sized–7). When I was in high school I was thin and I had all the same traits, crows-footed, upturned nose, round face. I also had some gait problems because I’ve had a slight tibia varum since I was a child (which my mom blames on me sitting with my calves outward). I was 5′ 4″ and weighed 120. (Now I’m 190–I got fat in college.)

  • carlos

    I’m not sure if my feet are pointed out. I think this is neutral. My nose is right, ever with hair from a teenager y have to shave from time to time. My feet arch is high. My face, I think square more than round and my shoe size is 42-43 in sizes usual in Continental Europe, I think in England this is as an 8, I don’t know how is this in the USA. My usual diet is fish cooked with olive oil, a light soup, milk, Iberian ham, excellent as another pork meats in small quantity, fruits, usually oranges or pears, very abundant and good in Spain, water and some beer and dry fruits. Beef I don’t taste now much nor eggs. Cattle meat is I think of no very good quality in Spain. I take some hamburger from time to time but very scarce, in travels mostly, airports, trains and speed situations. I practically don’t use sauces, as ketchup or mustard. I drink very little sodas, coca-cola, and so on.
    Today, I have self discipline if I had to do, as I have done a lot of stupidities and efforts in vain in my life with great efforts. Now, if that’s necessary to rise soon in the morning, I do, if not, no. I’m a nocturnal animal and I feel better by night. Big work problems in early morning are unavoidable, but if possible, I deal later with these, must of all, reading, writing and study problems more than action affairs. I read very much essays.
    When younger, I walked much and drove a car also much. Now, it’s impossible as this village it’s not Madrid and I’m older. As all Spaniards I played soccer football (badly. I’m too individual for team activities), a practically national sport in Spain although an English discovery. After all, Spain is actual World champion of football and possibly Europe champion in 48 hours with permit of Italy or Germany. I have with age the tendency my mother had and she lived until 89 years old. In bed I sleep I think no much, but seated, reading at less it was a thrilling book or before the stupid tv I use to sleep a short time.

  • Garden_G.nome

    The diet soft-drinks one is obvious. People think they are being “good” when they drink these things so are more likely to splurge on the calorific foods.
    How many overweight people have you seen that order piles of pizza and fries then have a diet soda with it? A LOT! Fat people also wear more jogging pants than healthier people, that does not mean they like to go jogging!
    Fat people are also more likely to have diabetes, so HAVE to stay away from sugary drinks and have diet ones instead.
    Interestingly, an article on going to the gym says that at the beginning people tend to get fatter because they reward themselves afterwards with icecreams and snacks, telling themselves that they have worked out so deserve it. Problem is that it takes several hours on a treadmill just to work off one teeny-tiny snack nevermind many. People soon work that one out after a couple of months.

  • carlos

    I have the idea that mental laziness is as important for obesity as lack of walking or physical exercise. I don’t believe very much in gymnasiums , as teachers there are prone to think you want to become a bodybuider in the fast time possible no matter if your’e 80 years old, so, from the first session, these are exhausting, excessive, brisk and non progressive exercises not rarely provoking lessions in prevously sedentary people.

  • Corina

    It is my personal observation that someone with long neck is always slim.

  • Vikki Stefans

    I have bad MCR4 and FTO snps and find that diet soda rasies my appetite. There is evidence that in many mice and at least some people artificial sweetener use increases insulin output and that of course induces you to crave more carbs/sugars and store them as fat. I remember when I first read about it, obvious confounders were being ignored, but it turns out that’s probably not the case.

    Through trial and error and adhering to a modified diet plus exercising a bunch, I got my BMI and body fat down to the upper normal range. My ideal weight is probably in the lower normal range though. Don’t know if I will ever get there or not. Just avoiding regaining will be require lifelong vigilance…worth it though, to have lower insulin resistance, have a better lipid profile that might not need a pile of meds I can’t tolerate, and not be diabetic (not to mention being able to find clothes that fit :-).

    I have big feet (9 1/2 to 10) for a 5′ 4″ lady but a small wrist (barely 6″). Max weight 216, current weight 144-145. I hope my current weight does not throw off anyone’s research on the influence of the abovementioned SNPs – my experience, including onset of obesity at or before kindergarten age, would suggest they are at least as potent as advertised in terms of promoting excess appetite and weight gain.

  • James

    Correlation is not causality. I have been in a health and weight management program for years. Having reached a “healthy” BMI previously, I looked and felt unhealthy. Friends were seriously concerned. Seriously concerned.

    As for the diet soda, I have suspected the correlation for some time. I read of a study of sweetners that indicated that the brain interprets the taste of sweet with safety. Thus, it could be a survival trait that seeks safety. Depression is likely the symptom of long term safety deprivation, particularly in a world of enormous numbers of information “threats”.

    All the traits listed certainly correlate with me. Luckily I found IHMOnline to manage BMI. I’ve kept 100 pounds off for 10 years.

  • http://www.lahope.com lahope

    My BMI is 20. I don’t drink any soft drinks, diet or otherwise. I have a high level of physical activity–yoga 6 x’s a week, spinning (indoor cycling) 7 x’s a week and twice a week sessions in the gym with my trainer who whips my ass. I also walk a lot. I totally watch what I eat: no junk food, portion control, low glycemic and nothing with added sweetners–even agave is a no-no, so discipline does come into play.

  • Jerilyn

    I choose to drink diet sodas over the regular ones due to the high sugar content. Regular sodas will give me urinary tract infections, while the lack of sugar in diet sodas keeps me free and clear.

  • Robin

    I’m 55 years of age a smoker and drink beer occasionally. However I never drink sodas and do eat lots of veggies and when I eat meat, I prefer non-greasy versions. My BMW is 22 today as I am 5’8″ and weigh about 145. However this weight is considerably more than when I was a young girl. I used to exercise daily. Today I don’t, so no matter what the BMW reflects, I know that I have more body fat. My feet have grown through the years from a size 7 to an 8. I have small bones. I dont think BMi is a tru representation of what’s really going on in your body.

  • LaDonna Keaton

    What is BMI ?

  • Aaron

    The thing in diet soda that I think makes people gain weight is CORN SYRUP! Not only is it a sugar that can cause weight gain but it seems to increase peoples apatite.

    • CP

      The whole point of DIET soda is that it doesn’t contain sugar, corn syrup or otherwise! It has artificial sweeteners instead.

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