Fats are essential for a number of bodily functions, and as such, their presence in the body is vital to good health. Fats are a concentrated energy source, they are key to a number of cellular functions, they ensure proper functioning of the nerves and brain, and also are vital to hormone production and regulation. A person devoid of fats would suffer a number of health consequences; and feel lethargic and depressed on top of that. The general consensus for healthy living and of the fitness community is a diet comprised of approximately 30% of its caloric intake from dietary fats. However, it may not be necessary that we eat nearly this much, and doing so may hinder our weight loss goals.
One of the problems with dietary fats is that they are extremely calorie dense. Just 100 grams of fat has a whopping 900 calories, as opposed to its protein and carbohydrate counterparts that have only 400 calories per 100g. In addition to that, fats are very slow to burn, so a surplus of fat at a meal will leave you loaded with calories for hours to come, also making them a poor energy source. Eating just a small amount of fat leaves us with a large amount of calories to burn through in order to achieve a caloric deficit, and in turn, lose weight. So what happens if we don’t eat enough fat as our body needs? Being that the body needs fat, if we don’t get it in our diet, it must get it from somewhere, so it turns to body fat, of which most of us have plenty. We can store very little carbohydrates (in the form of glycogen), virtually no protein (unless you count what’s in the muscle, which we definitely don’t want to use), but we have copious amounts of stored body fat, which our bodies have evolved through history to store for use in times of famine. Your body is always either burning body fat or storing body fat to some degree and as such, there is always fat either going into or out of our fat cells. If fat begins to accumulate in the bloodstream and is not burned, it will be deposited in adipose tissue. Conversely, should free fatty acids in our bloodstream get too low, the body will pull them from the fat stores for just such a situation. Your body doesn't do much to change the nature of the fat you eat, so the fat we eat is essentially the exact fat we have stored. So if you need it for something useful (like building cell walls or neurons, or your workout, for example) then your body uses the fat in the bloodstream for that. Once this fat is mobilized and in the bloodstream for use, the body cannot decipher where it came from.
One exception to this is the inclusion of essential fatty acids (EFA’s) in the diet. These are the omega 3-6-9’s. EFA’s are fats that are required for biological processes, whereas all other fats are specifically used for fuel. There needs to be firm distinction made between EFA’s and other fats, as their function in the body and necessity in the diet differ greatly. These are essential to body processes and cannot be stored nor synthesized in the body. For that reason, on a highly fat-restricted diet, supplemental EFA’s are necessary for good health. However, these are always a good idea to supplement with, regardless of dietary fat restriction.
As a rule, the higher our body fat percentage, the more we can restrict our dietary fat healthily and safely as a tool for weight loss. A 200lb individual at 20% body fat has an astounding 40 pounds of body fat, 25 pounds of which they can healthily do without. That equates to 102,058 calories of stored energy, enough to live for seven weeks at 2,000 calories of energy usage per day. This individual would not really need any dietary fat except EFA’s. The more fat we have available, the easier it is to draw from it for energy and body functions. As body fat supplies diminish, they become less readily available, and subsequently more difficult for your body to access in situations of high demand. For this reason, the amount of dietary fats we need is inversely proportional to our body fat percentage. Above 12-15% body fat or so, we really only need supplemental EFA’s and trace amounts of other fats, as we get into the single digits, however, it’s a good idea to increase this number accordingly.
Overall, the necessity of ample amounts of fats in the diet has largely been overstated. While fats are very important, especially EFA’s, we can generally pull what we need from our body fat stores. Taking dietary fat levels to low levels can generally speed up fat loss significantly. If you are over 12% body fat, try reducing your dietary fat intake to low levels and allow your body to draw more from stored body fat; the chances are you will lose weight faster and easier.