-cultivate discipline
- healthier cardiovascular system
-elevates mood
-increases metabolism
-able to counter obesity
-expand social circle
-slow down ageing

( hopefully this points help :) )

First write a short greeting to your friend. a short hello is fine.
Next, you should say that you noticed how your friend is skinnier and not as strong as she used to and you are worried for her health condition.
Therefore, you are willing to tell her how she can increase her health by trying not to eat too much sugar intake and plan out oñ a  a balanced diet. 

Exercising regularly is also a must. exercising at least once a week is enough so that your friends stamina will increase phenomenally. writr yiur hope for your companion and you are done. hope this helps.