There is no single "best" food for gaining weight, as the best diet for weight gain will depend on an individual's specific needs and preferences. However, some nutrient-dense foods that can help with weight gain include: Lean proteins such as chicken, fish, lean beef, and eggs Whole grains such as quinoa, oats, and brown rice Healthy fats such as avocados, nuts, and seeds Dairy products such as milk, yogurt, and cheese Fruits and vegetables, which provide important vitamins and minerals Starchy vegetables like sweet potatoes, yams, and potatoes Legumes like lentils, beans, and peas