Hi.. I'm very glad at this age you know how important it is to be healthy & fit.
A proper diet & exercise plan will help you achieve your target and understand the cause of breathlessness.
Maybe the reason for breathlessness must be the type of exercise / intensity / meal imbalance / suddenly exercising a lot after long.
Next Steps
Do not follow any crash / detox diets without guidance. Consult a Dietician for right advice.
Health Tips
Start with basics:
1. Add adequate vegetables & protein rich foods in your diet.
2. Cut down on junk food (biscuits, chips, fried foods,etc)
3. Start slow with basic walk, swim, cycle for 30 minutes