Obesity could be defined in terms of weight alone. What would be wrong with this?

I am doing an assignment on obesity and bmi, and need some help with this question. I no what i want to say but can't find the right words, thanks in advance if anyone can help xxx

Take height and the frame and if their sex into consideration when doing your assignment.

There's a huge difference between a 6'3" 250 lb linebacker that's all muscle, and 5' 250 lb couch potato who's never exercise a day in his life.
And no, it's not just the weight
Think about that.

Weight does not determine somebodies body fat content of Body mass index. For example a person can weigh 13 stone and either be really tall ans stocky, short and fat or just average. It depends on the build. I weigh 11 stone and 5 10 or something around that and have really muscly legs and broad bones (unfortuately) but I could weigh the same and be classed as very overweight.
I would speak to several people (preferably friends who aren't weight conscious so as not to offend) ask there weight and height and then you have a rough guide about different people. Also look on the internet for people who known sportmen/women and then write about their weights and why they are not obese. Muscle weigh more than fat as well...

unfortunately the ignorant masses of the US have once again taken something like the BMI and turned it into something it was not designed for. the BMI is only effective for addressing the health risks that are associated with central obesity, that's it. the BMI is not a gauge for health or fitness nor is a lower BMI better than a higher BMI if you are not obese. for some reason people seem to think that a BMI of 18 means that you are healthier than when the BMI was 22 and that is not the case. since the BMI does not take body composition into account it is a rather inferior method of determing health risks as compared to the body fat percentage for the non-obese individual. a person can have a BMI of 18 with 30% body fat because they have a complete lack of muscle mass.. another can have a BMI of 32 (like myself) but have single digit body fat.

for the non-obese individual the body fat percentage is a far more accurate method to determine the current health risks. the BMI only works for those who are not obese and with average to below average amounts of muscle mass. the body fat percentage works for everyone regardless of the body composition

Now, health care professionals are coming round t the idea of using a hip waist ratio system instead of BMI as BMI does not take into account how much muscle a person has, as this weighs more than fat, and yet is much healthier, so even if 2 people had the same BMI, maybe both considered over weight or obese, they would both be considered to be at higher risk of heart attack, stroke, diabetes etc, yet if one was very muscly, it wouldn't give a true picture of his/her risk for these diseases. Hip waist ratio looks at how fat is deposited around the abdomen compared to the hips, as a large amount of fat around the abdomen highers the risk of the diseases I mentioned before. Hope you understand this-I do waffle a hell of a lot

I have spent a lot of time lifting weights and have become quite muscular. I am quite heavy for my height and I know I need to lose some weight but I am not as overweight as my height and weight alone would indicate.

If you define obesity in terms of weight alone, you are ignoring the fact that some people have a good deal of muscle mass. Muscle is more dense than fat, and weighs more, so you could appear to overweight by sheer numbers, yet have relatively little body fat, therefore not being obese.