Why we need foods high in Fat ?

Fat plays several roles in the body, including that of being a source of energy long term. Lipids are in fact the nutrients that produce the most energy when they burn (1g of fat = 9 kcal of energy). They are used primarily on long efforts because the reserves of carbohydrates are used first.

It is considered that the daily intake of fat should be 1g per kg, or 40g for a 40kg person.