Best/Healthy way to gain weight?

Try eating 6 meals per day. and drinking juice or milk to meals. 

eat lots of healthy fats -nuts.avocado. salmon.etc etc - eat carbs -potatoes.pasta. rice . bread etc etc 

and adding oil & butter. & cream to meals.

yogurt.milk.ice cream are all good to eat

eat plenty of protein as well!! And try to work out and do weight lifting to gain muscle!

eating chocolate/crisps etc etc is good now and again if you need to gain weight. but not all the time. 

snack ideas - dried fruit and nuts  

yogurt + granola  

fruit salad with yogurt and.muslie  

milkshakes  

smothies  

Sandwiches  

granola bars  

flapjacks  

etc etc

have you ever heard of fortimel or ensure? there high calorie & fat supplement drinks. they help if you need to gain weight. but i think you need to talk to a doctor about them.

Good luck anyway!:)