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.