Bill and Sarah are a happy couple enjoying their life together. They workout on a regular basis at Gain's Gym and have noticed an explosion of huge muscular men and bimbos at night.
One night they notice that their protein powder is low but the fitness stores are closed. When they arrive at Gain's Gym, they discover a new promotion regarding a line of protein powder from Bigger the Better. With a one-week free supply in hand Bill and Sarah head home after a quick workout.
A few days later they decide to give the free sample a try. The results are quite shocking at first. Bill gender swaps into Charlotte, a busty blonde with curves that do not quit. Sarah gender swaps into Nathan, a hunky body builder.