Weight gain might be due to medical issue as well.
To maintain your health follow the undermentioned points:-
1. Avoid cauliflower, cabbage, broccoli, soya bean in your diet,
2. Start some physical activity daily for 20 minutes.
3. Drink at least 8-10 glasses of water everyday.
4. For constipation
take 2-3 tsp wheat Grass Juice ( Available at organic shops) with warm water every night and see the changes.
5.Avoid junk food items completely.
6.Take 2 servings of fruits every day.
For it will help.