There are plenty of excuses.
I'm 6'6", had a 6 pack when I was 20, and weighed 100kg, and was pretty fit with a low fat index. I was easy BMI then (100/2^2, 25), but BMI was irrelevant, because I was relatively fit and active. I'm still easy to calculate BMI, but weigh 115kg or so now. 5kg more, and I hit obese.
Now, I would like to lose a little weight, but I put on a bit of muscle in my 20's. I don't think I could ever hit a decent BMI.
I eat/drink probably about 2000kcal/day, but I'm not that active currently. I used to do physical work regularly (and ea a whole load more), but don't currently.
I know that if I eat a lot, I will get huge. I don't.