There can be many reasons for your weight gain. I am happy that you are staying in happy mood (prasanna-chitta). It is profitable to do hard work with the body. One who wants to keep healthy mind and wants to do sadhana, needs to give lot of importance to hard physical activity. It is definite, that the idle soul will not be able to do sadhana. Many years back, I was visited by man who used to get many bad thoughts in his dreams. He asked me, for the solution of this problem. I told him to work so hard, that his body will be very tired at the days end. This way, he will have improvement in his thoughts during day and also in the dreams. I also instructed him to come back after trying this method. Idle mind keeps thinking a lot and when we are busy with physical work, it does not have as many thoughts. It is a matter of tremendous gain, if we stay engaged constantly in the work. One who work, casts a spell on others. This way you will be well liked and loved by others. They will have good feelings for you. All these is not a trivial matter.
Pujya Shree Mota
Jivan Mandan
Edition 3; Page 106.