Get older. 
Seriously, under about 25 it is quite hard for most people to gain, as the metabolism is at its fastest. Once into the mid-20s it slows right down and the weight really creeps on, whether you intend it to or not.
Seriously, under about 25 it is quite hard for most people to gain, as the metabolism is at its fastest. Once into the mid-20s it slows right down and the weight really creeps on, whether you intend it to or not.
12 years