Eating fat does not make you fat. It's your body's response to excess carbohydrates in your diet that makes you fat. Your body has a limited capacity to store excess carbohydrates, but it can easily convert those excess carbohydrates into excess body fat. It's hard to lose weight by simply restricting calories. Eating less and losing excess body fat do not automatically go hand in hand.
Diets based on choice restriction and calorie limits usually fail.
People on restrictive diets get tired of feeling hungry and deprived. Weight loss has little to do with willpower. You need information, not will power. If you change what you eat, you don't have to be overly concerned about how much you eat. Adhering to a diet of low carbohydrate meals, you can eat enough to feel satisfied and still wind up losing fat-without obsessively counting calories or fat grams.