I lost weight on a modified Paleo diet. From around 270# down to 175# at my lowest point. My doctor eventually told me to gain some weight back.
Calories are important but all calories are not equal. Some things like beans will pass through the digestive tract with minimal digestion occurring. Other foods will be completely digested very quickly such as pasta and white bread. When I eat grain foods now, I try to eat ones that are very coarse in nature. One key is to know what you are consuming. For a week or so, weight everything that you eat and see where calories are sneaking into your diet.
What did it for me was looking at the glycemic index of foods. When you consume any food, digestion starts and if carbs are involved, there is a correlating increase in blood sugar over time. A prime example is quick oatmeal. The oat grain is steamed, rolled and chopped into small pieces. As it is digested, the starches in each small fragment are converted to sugar very quickly. Compare this to steel cut oats. The same exact amount will digest at a slower rate as it takes time for the enzymes to penetrate the oat particles. By eating low glycemic index foods, insulin production is minimized and you get off of the insulin roller coaster. When I was dropping weight like a rock, I was never hungry. I did eat snacks between meals but they were always low GI foods.