Building a body is not so difficult but the determination to do so does not come easily. Here are some tips if you follow that your metabolism will eventually increase and that will help you build up your determination.
1) Take jaggery with warm water mixed turmeric in it.
2) Take a good fruit shake in your breakfast with oats.
3) In lunch whatever food you are taking, take it in a proportional way so that you can eat everything served to you.
4) In the evening you can take green tea.
5) At dinner, you should take light food.
6) Just before going to bed take a glass of milk and a few nuts.
With all these, you should be doing regular exercise and a decent time for walking after every meal.
This will help you to get the energy and strength and determination so that you are fit enough to go to the gym and hardcore workout.
This is for the preparatory phase before actually starting to do the gym.
All these might sound weird but this going to enhance your efficiency when you start gyming.