You need to check up your thyroid profile as hypothyroidism can cause weakness, weight gain and many issues.You need an extra 500 calories a day if you want to put on extra weight in a week. - Protein is the key for muscle building; it will help you gain muscle weight rather than fat mass. Good sources of protein are red meat and poultry, eggs, whole grains. Salmon is high in calories and healthy fats.
Best Healthy Foods to Gain Weight Fast
Homemade Protein Smoothies. Drinking homemade protein smoothies can be a highly nutritious and quick way to gain weight. ...
Milk. Milk has been used as a weight gainer or muscle builder for decades. You may also include rice, nuts and nut butter, red meats, potatoes and starches, salmon and oily fish, and protein supplements.