I think anyone can do it, barring some serious medical reasons. But my point is, for some it is very easy, others not so much. I say this as someone who could drop 30 lbs easily with diet and exercise when I was younger, but now find it much more difficult.

And the variation can amount to quite a bit. All it takes is time. An excess 100 calories a day adds up to 10 excess lbs in a year. 5 years down the road and you are 50 lbs overweight.