Even though there are major differences in the various types of fats, you should almost always keep your overall fat intake relatively low (30% or less, preferably closer to 20%). There are eight primary reasons why:
1. Fat is more calorie dense than any other source of calories.
After reading chapter six on calories, you now understand that to lose body fat you have to eat fewer calories than you burn each day. One problem with fats is they are more calorie dense than any other food. Each gram of fat contains 9 calories, while each gram of carbohydrate or protein contains only 4 calories. Since each gram of fat contains more than twice the calories, this means eating fat makes it more likely that you'll eat too many calories. Quite simply, a high fat diet is a high calorie diet, and a high calorie diet is a fat storing diet. There are differences between the various types of fats, but ALL fats contain 9 calories per gram. So if you want to lose body fat, you'll need to reduce your total fats in general in order to keep your calories down.
Fats are stored more easily as body fat than protein or carbohydrate because they have the lowest thermic effect of any food. Recall that the thermic effect refers to the amount of energy required to digest and utilize each food. Protein has the highest thermic effect - nearly 30%. Fats have the lowest thermic effect - only 3%. When you eat lean protein foods, 30% of the calories are burned off just to digest and absorb them. When you eat fatty foods, only 3% of the calories are burned off during digestion and absorption.
3. Saturated and processed fats (trans-fatty acids) cause serious health problems.
Certain types of fats, especially the saturated fats and trans fats, are bad for your health. According to Dr. Erasmus, "Degenerative diseases that involve fats prematurely kill over two-thirds of the people living in affluent, industrialized nations." Saturated fats have been linked to heart disease, cancer, diabetes and too many other problems to list.
4. A high fat diet doesn't leave room for enough protein or carbohydrates
High fat diets are often promoted as effective ways of increasing anabolic hormones and controlling fat storing hormones, resulting in increased muscle mass and decreased body fat. The problem with this approach is that eating large quantities of fat doesn't allow enough room within your daily calorie allotment for a sufficient quantity of protein or carbohydrate. Any diet that leans excessively towards one macronutrient is not a balanced diet and will never produce optimal results.
Insulin sensitivity refers to the responsiveness of your muscles to insulin. Insulin carries the sugar into the muscles for energy and glycogen storage. It also carries the amino acids into the muscles for growth and repair. When you have poor insulin sensitivity, it's like insulin is standing outside with protein and carbs, knocking on the muscle cell's door, but the muscle cell won't let the insulin bring the carbs or protein (aminos) inside. So blood sugar continues to build up, and you release even more insulin to try to get the nutrients into the cells. Not only are the high insulin levels disastrous to your fat loss efforts, severe insulin sensitivity is essentially an early stage of diabetes.
6. Dietary fat gets stored more easily as fat than any other nutrient
Dietary fats DO get stored as body fat more readily than other types of macronutrients. This isn't just due to the high calories, it's because the process of converting dietary fat into body fat is chemically very easy. Body fat is made of glycerol and fatty acids. Dietary fat is made of glycerol and fatty acids. There's no costly energy conversion that has to take place. This makes dietary fat very easy to store. Too much of anything gets stored as fat, but foods such as lean proteins and complex carbohydrates must go thorough a metabolically costly process to be converted into body fat.
7. Dietary fat is not an efficient fuel source for high intensity muscular work
Muscle glycogen is the primary and preferred fuel for high intensity weight training. Fats are the primary fuel source during prolonged aerobic exercise, but fats do not fuel high intensity weight training. If you're eating high fats at the expense of complex carbohydrates, your glycogen levels will diminish or be completely depleted and your training will suffer. The high fat diet cultists will attempt to persuade you that dietary fat in the absence of carbohydrate will become the primary fuel source. They are often fond of saying, "There's no such thing as an essential carbohydrate, but there are essential fats and essential amino acids." The truth is, carbohydrates ARE essential for high-powered anaerobic workouts in the weight room. Ask any bodybuilder who has been on a very low carbohydrate diet; when no carbohydrates are eaten, their energy goes down the toilet.
8. Large amounts of dietary fat do not assist muscle growth
The high fat cult says fats are anabolic, referring to the fact that fats are necessary for normal muscle building hormone levels. An extremely low fat diet suppresses anabolic hormones such as testosterone - that much is true. They fail to mention that only small amounts of essential fats are needed for anabolic hormone release. When the fat in the diet is high, it's actually non-anabolic. Here's why:
When fat is high and carbohydrates are very low, there's nothing to stimulate a moderate insulin release. Fat has very little effect on insulin. In order to drive the amino acids into the muscle cells where they can be used for muscle growth, a moderate release of insulin is necessary, and only carbohydrates produce enough insulin release to shuttle those amino acids into your muscle cells. It's ironic, but so-called "anabolic" high fat diets are anything but muscle promoting.
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