What are some low calorie foods that are filling?

Salad, etc.: You can eat all the salad you want, just use lemon juice as a dressing or a small amount of olive oil and some vinegar (i like balsamic vinegar). Vegetables such as asparagus, brocolli, cauliflower, string beans, spaghetti squash, sweet potatoes, brussel sprouts are good, too, but be careful what you flavor them with. A little butter is fine as is lemon, salt & pepper.

Greens: Green leafy vegetables. However its not about calories it is about macronutrients: fat, protein, carbohydrates. Each macronutrient has sub groups. It is about eating the right macronutrients in proper amounts and not counting calories.