What's the best foods for a family if one person is trying to lose weight, while another is too skinny and wants to get fat?

Count calories. There is no substitution for a healthy diet, regardless if the goal is weight gain or loss.Weight gain is achieved if the individual takes in more calories than he/she burns; weight loss happens when calories burned exceed calorie intake. Calculate calorie needs for each family member from the nih website then eat the same food. Dieter needs to exercise; supplement calories for the too skinny one.