There is a reason that Protein, carbohydrates and fats are considered macromolecules because all three are considered essential to humans. No fat diet or low fat diet rarely work as the body then starts working against oneself.
As fats are essential to the body, in its absence, the fat reserves in the body are used up. Taking healthy fat in proper ratio actually helps aid in weight loss. Healthy fats like olive oil will stimulate bile flow to improve digestion and breakdown fats properly. Good fats also contain HDL cholesterol (good cholesterol) that circulates through the body and helps get rid of plaque deposits on blood vessels.
Vitamins and minerals also are important in diet. Fat soluble vitamins use oils and fats in our daily foods for transportation to target organs. Without these good fats to carry and store certain vitamins, nutritional deficiencies may occur. Fat soluble vitamins are A, D, E and K. Also such essential nutrients are found in fats such as omega three and omega six fats.
Quality ways of getting healthy and quality fats are through olive oil, flax seed, and fish oil.
It is always important to keep the fats in diets in a good ratio. Fat is a long term source of energy so higher ratios can be used for atheletes. Non hydrogenated oils, non trans fats and non saturated fats should be focused upon in the diet to keep lipid intake in limit and limit to essential and quality fats.