BMI and BF %

[Hercules]

How can a male teen at 17 have, a 13-15% body fat percentage which is considered healthy(iirc) but have a BMI of 18 which is classed as underweight and not healthy?

Correct me if im wrong but both methods measure a representation of an individuals bodyfat which is determined by caloric intake?

One method (bf %) say your eating enough because you are spilling excess calories then what your body needs into visual fat on your body and other method (bmi) suggests you could be starving yourself because you are too light for your height?

[Phedder]

They're entirely different, bodyfat percentage has no mention of total weight, just what percentage of that total weight is fat. Conversely, BMI has no mention of bodyfat percentage, it's just a ratio of your weight compared to your height. So if you're skinny, but don't carry much muscle mass, chances are you'll have a low BMI with a 'healthy' bf% and if you're carrying a lot of muscle mass, you're BMI may class you as overweight or obese, but your bf% is also well within the healthy range, or for many here quite lean. 

BMI is only useful on a population scale, as it gives an easy to measure representation of the bodies of a population, however on an individual basis it's pretty much meaningless, especially if you're at all athletic. Most of the All Blacks are 'obese' by BMI standards. 

[AZIDE]

They're entirely different, bodyfat percentage has no mention of total weight, just what percentage of that total weight is fat. Conversely, BMI has no mention of bodyfat percentage, it's just a ratio of your weight compared to your height. So if you're skinny, but don't carry much muscle mass, chances are you'll have a low BMI with a 'healthy' bf% and if you're carrying a lot of muscle mass, you're BMI may class you as overweight or obese, but your bf% is also well within the healthy range, or for many here quite lean. 

BMI is only useful on a population scale, as it gives an easy to measure representation of the bodies of a population, however on an individual basis it's pretty much meaningless, especially if you're at all athletic. Most of the All Blacks are 'obese' by BMI standards. 

^This

Its because you have f*ck all muscle. you should try actually lifting and eating instead of posting stupid questions every week. 

[Leeroid]

The idiocy in the OP blows my mind

[FellowshipOfTheRon]

internet can be awesome for helping you learn lots of good stuff but plenty of info here that'll just confuse you and help towards your tendencies to overcomplicate shit. you are 17 very young, just eat lift sleep and grow man(+study hard in school too!)

[Pseudonym]

Bit harsh, guys! If he's only 17, and only made half a dozen posts, I think you need to give him a chance.

As Ron says, I'm picking this is a case of enthusiasm + wanting to do it "exactly right" + internet = over analysing. But the point is, it started from enthusiasm, and that's a very good thing.