Yogurt

Full-fat yogurt can also provide protein and nutrients. 

Avoid flavoured yogurts and those with lower fat contents, as they often contain added sugars. Yogurt is a staple in our weight gain food list and can be eaten as a delicious salad dip:
Whisk full-fat yogurt until it is creamy.
Add cucumber, carrots, beetroot and crushed pepper.
Add ranch dressing to it and serve with sliced carrots and chips.