weight is weight...... a 5'10 275 lb person with 9% bf and a 5'10 275 person with 30 % bf are both obese.......medical definition of obesity never metions bf..... google it ...... the def of obesity is 20% above your ideal weight.........your heart, lungs and body functions don't know the difference between muscle and fat......... bodybuilders are obese by any definition....when someone 5'10 275 lbs muscle or fat can't walk up a flight of stairs without being winded they are obese