How can limiting ones intake of saturated fats help fight against obesity and being overweight?

If calories are less: Limiting one's intake of saturated fats helps fight against obesity only if the person is not eating non-saturated fats instead. Fats are fats, so saturated fats have the same number of calories as non-saturated fats. Substituting one fat for another fat won't change obesity. One would have to substitute with protein or whole-grain carbohydrates, to get fewer calories and loose some body fat.