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While Body-Mass Index isn't the worlds most accurate indicator, it does correlate quite nicely with body fat, as the graph below shows.

BMI vs Body Fat %

One of the uses of BMI in this case, is that a high BMI is generally considered to be correlated with poor health outcomes, especially cardiac problems. However, it is common for people to point to athletic outliers as an indication that BMI is flawed.

However, even with a high-weight and a low body fat, the heart still has to do more work to pump body through a larger frame. As such, is there any research that looks at the link between individuals with a high-BMI and low body fat, and health?

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I don't think your question makes sense. You mean, does being a short muscular person (heavy, but low fat), have an increased risk then a taller muscular person? – user7050 Mar 17 '14 at 5:21
@LazyMan No the question is more along the lines of: Are there health differences between two people, of the same height and body fat percentage, but with one being "obese" and one being "normal" according to BMI? – Lego Stormtroopr Mar 17 '14 at 5:23
But its more along the lines of "does a high BMI correlate with poor health outcomes, regardless of body fat make up"? – Lego Stormtroopr Mar 17 '14 at 5:24
A high BMI is 'generally related with poor health outcomes' because people generally don't have high mass/low BF%. Only certain athletes share these characteristics (e.g. strength athletes, bodybuilders) which makes the application of the BMI for these people pretty absurd. There are adjusted BMI scales for strength athletes or paralyzed people, though, which just goes to show how arbitrary this whole BMI business is. – LarissaGodzilla Mar 17 '14 at 7:40
@LarissaGodzilla That's the question, is there a study that looks at the correlation between BMI and health outcomes AND ALSO controls for body composition. – maxywb Mar 17 '14 at 18:47

To the best of my ability, I've not been able to find a study that thoroughly looks into this issue. However, BMI is a poor indicator in and of itself for a multitude of reasons. I'll enumerate some of them: (a) visceral fat is far worse than subcutaneous fat in terms of health. (b) too little fat is also bad for your health, but the odds of your BF% entering the into the essential fat levels is rather small and requires extreme effort or starvation. (c) heart health depends on more than just body fat, Cholesterol levels, stress and cortisol levels, additionally, the amount of cardio that you do has a profound effect on heart health. So, you could have a high BMI a 10% body fat and be a high risk of heart attack. Furthermore, regardless of what the tissue is, any addition of vascular tissue results in greater strain and work that the heart must overcome in order to pump blood through your body. In terms of heart health, BMI is poor indicator as it tells you little more than what you could learn from a mirror. If you're concerned about health, and heart health, consult a physician to have them do a cardiac stress test and run bloodwork. For example, congestive heart failure occurs

As for orthopedic health, BMI correlates better and has a great possibility of causation due to the fact that body mass is among the largest contributors to orthopedic issues after diet, exercise, and genetics (Joint problems). Too much mass and your body will be overstressed, too little mass and your bones will be weaker due to decreased stress loads resulting in less calcium being transferred into the bones (Osteoporosis).

TL::DR: regardless of composition, increased mass results in greater work on the body. Greater persistent work causes greater stress, greater waste, etc. The problem comes with finding balance between exercise and muscle gains (hypertrophy) and inactivity (atrophy). Generally, inactivity is worse for your health than too much body mass. Ultimately, any concerns you have regarding health is best suited for a doctor who can run tests and make objective evaluations in addition to subjective evaluation.

This answer is based largely off of my experience as a paramedic and being a biomedical engineering student with a minor in pre-med. I apologize for not being able to come up with a definitive study, but I suspect there aren't many since high muscle low fat people aren't nearly the health concern as obesity and high fat people.

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