Eating greater amounts of food and increasing your protein and calorie intake help in building muscle mass, and thus, increasing your weight. It is not advisable to gorge on unhealthy trans-fats like fried chips, cookies, and processed foods as these will cause obesity rather than building healthy muscle mass. Whole grains contain high amounts of glucose, which acts as your body’s main dietary source of energy. Nuts contain significant amounts of calories in a small serving. Two handfuls of almonds or around 18 cashew nuts can provide 160 calories.This Avocado is rich in fat and calories. An average avocado contains around 300 calories and 31 Potatoes are the richest source of carbohydrates and complex sugars.grams of fat.Smoothies are an excellent option to consume extra calories without adding solid food to your diet. This fragrant, silky, and tasty dairy product is loaded with saturated, monounsaturated, and polyunsaturated fats. It is also a good source of vitamins A, B12, E, K2, and D, minerals such as calcium, phosphorus, and potassium, omega-3-fatty acids, and omega-6 fatty acids. Butter contains around 100 calories per tablespoon, and will definitely help in gaining weight.