Eat full well balanced meals and exercise. Meals that are heavy in complex carbohydrates such as pastas using whole grain is best, don't forget deserts such as cooked puddings or old fashioned donuts. Utilize high protein drinks such as Ensure. Doing all this just don't forget to exercise because that will distribute your weight gain over your whole body

Try adding Ensure to your daily meals, worked for me.

Hi , I have exactly the same problem, 120 pounds to 85/ 90. Tried Ensure, helps a little but I get so out of breath trying to eat. Down to eating once a day because of mucous in throat and breathless. Plus have dysphagia so everything must be pureed. Cannot bathe myself, do chores or cook. Rarely leave house. Doctor not much help and no lung doctor available yet. Mine retired. Not on oxygen- they refuse to prescribe it. Use a walker. Can't even shop in a store anymore.
I wish more help was available. Home care is too costly, so husband does everything. It is hard on him and house is dusty and needs a huge deep clean. Am likely stage 3, close to 4. Very severe is all they'll say.
Ver6 hard, especially at holidays.

I drink Carnation Instant Breakfast . It has the same nutrients as ensure if not more and it taste good

You can also check with a nutritionist to get ideas of high calorie foods that won't spike your sugar or carbs too much and help you maintain a balanced diet.