I feel so full after eating so little

There may be times when you seem to fill up fast even though you used to be a big eater. It is important to maintain your weight by choosing high-calorie foods and foods that are rich in nutrients.

Eat only foods that are rich in calories and nutrients. Avoid low-calorie foods that fill you up, such as lettuce, broth, and diet soda.
When choosing beverages, select nutrient-dense fluids such as milk, milk shakes, juice and punch-type drinks.
Limit the amount of fluids you drink with your meals. Liquids tend to make you feel full. Save the water, tea, coffee, and other liquids for between meals.
Place small servings of food on your plate so it does not seem to be such an impossible task to eat a whole meal. Cut sandwiches into smaller pieces.
Keep ready-to-eat snack foods readily available, and even at your bedside in case you wake up during the night. Ideas include pretzels, nuts, crackers, cookies, dried fruits, granola bars, and rice cakes.
Eat small amounts of food frequently.