Gaining weight quickly and safely requires a balanced approach that focuses on increasing healthy body mass rather than relying on junk food. The most important step is to eat more calories than your body uses each day, but in a nutritious way. You can do this by including foods like milk, curd, paneer, eggs, chicken, fish, dal, nuts, seeds, bananas, rice, potatoes, and whole grains in your daily meals. Eating smaller meals 5-6 times a day instead of 2-3 heavy meals can also help you take in more calories comfortably. Adding healthy fats such as ghee, peanut butter, olive oil, and nuts can further increase calorie intake in a healthy way. Along with diet, regular strength training exercises like weight lifting, squats, push-ups, and resistance exercises are important because they help build muscle and improve body weight in a healthy manner rather than just increasing fat. Getting proper sleep is also essential, as the body repairs and builds muscle during rest. Nutritional drinks like milkshakes or banana smoothies can also support weight gain if taken regularly. Supplements should only be used after medical advice to ensure they are safe and suitable for you. If you are not gaining weight despite eating well, it is important to rule out medical causes such as thyroid problems, digestive issues, or other underlying conditions with a doctor's help.