Not all calories are created equal and fat calories will have much more of a negative impact on your weight loss than calories from either protein or carbohydrates. Fat contains 9 calories per gram while protein and carbohydrates only contain 4 calories per grams which means you can eat over twice as much food containing protein or carbohydrates to equal the same number of calories as food containing fat. This also means that food containing protein or carbs will fill you up much faster because they are less dense in terms of calories. The other problem with eating fat is that it is much more easily stored by the body as fat because it does not have to be converted to fat for storage like protein or carbohydrates. It actually requires energy to convert protein or carbohydrates into fat for storage so this further reduces the caloric impact of protein or carbohydrates so the actual negative impact of eating fat may be as high as three times as much as eating protein or carbohydrates. It is also important to differentiate between saturated fat and unsaturated fat. The name saturated fat means that the chemical makeup is completely saturated which ultimately means that this type of fat can only be used for energy so when you eat this type of fat it will either be immediately used for energy or stored to be used for energy at a later time. What all of this means is that if you consistently eat foods containing a high amount of saturated fat then you will most likely be overweight. You can reduce your total caloric intake all you want but if you do not significantly reduce the amount of saturated fat that you eat every day then you are going to have a very difficult time losing weight.