Your body is a gym, so use it! Push-ups help to build your upper body strength, specifically your triceps, pectoral muscles and shoulders; they also help strengthen your core and lower body through slight modifications.
The point of this is not to exercise, right? Wrong! It is to do the least amount of exercise to get the most gain possible.
We want to convert the food you are eating into muscle instead of fat. Doing these exercises and following the supplement regime will accomplish this efficaciously.