Suggest Treatment For Recurring Diarrhea And Vomiting In A Child

Question : Our 16 year old son got what the doctors believed was food poisoning on feb 23.
He remained pretty sick with vomiting and diareha for the next few days and had no appetite for about a week after he broke his fever.
He has gotten back to eating pretty normal again but he does say he doesnt seem to have quite the same desire to eat (like a teenage boy) as he did before he got sick.
To date it has been 3 weeks since he got sick. He is also back to playing sports and says he feels good but not quite where he was before the illness.
We also noticed he lost about 7-10 lbs.
Is this a normal recovery from food poisoning? How long does it take to feel 100% and to start putting weight back on?

I guess our biggest concern was that initially he seemed to hold his weight. Once he got over fever and a few days of still feeling tired and weak, he returned to participating in basketball and was almost the same "muscle mass wise".
He has continued playing and does state that he feels good but we now notice he evidently lost some muscle mass and weight along the way, and when we ask him he says his appetite may still be slightly reduced but that he feels ok and is eating pretty normal( we are used to him eating a lot being he's a growing young man).
Being that he is a teen, and more independant, and in control of his own diet, we arent exactly sure how long he hasn't consumed as much as he was before getting food poisoning.
To my XXXXXXX he seemed to have lost most of the weight after he was no longer sick but during the weeks recovering.
Now im realizing maybe he shed the pounds due to reduced calories over the following weeks because of a decreased appetite.
Maybe returning to training had an impact as wel.
Does that sound right?
Should he be taking probiotics and or yogurt to get him back in balance?
He isnt training really hard but he is doing moderate exercise of about an hour per day, 3 times per week.
Thanksl