If you consume too much of any one food or ingredient, you can get sick. Even drinking too much water, one of the most innocuous substances on earth, can be bad for you. It's also possible to not consume enough of any one substance, which leads to nutritional deficiencies and health problems. Moderation is key.

Most experts think that a diet that contains 25 to 35 percent of your calories from fat is the healthiest. For our purposes, the limit will be 30 percent calories from fat. Saturated fat has its own limit; most experts think that less than 10 percent of your total daily calories should come from saturated fat.

Table 1–1 Fat Grams per Calorie Intake

Recent Studies

Some high-profile large scientific studies have showed no difference in the risks associated with cancer, heart attack, and stroke between a group of women who ate low-fat diets and those who ate whatever they wanted. This study, like many others, just proves that a diet rich in variety and whole foods is probably the best for you throughout your life.

It seems that almost every day the media report on a new scientific study that directly contradicts established wisdom. What are you supposed to do? Science doesn't progress in an orderly fashion. Theories change as new studies prove different conclusions. All you can do is keep eating whole foods, a balanced diet, and fresh foods. If you eat a colorful plate and vary your diet, you'll automatically eat about 30 percent calories from fat. You'll also feel satisfied, have more energy, and be able to maintain a healthy weight.

Think of food as a balloon. Food is made up of fat, proteins, and carbohydrates. If you cut down on one, the others automatically must increase. If fat in a food is reduced, it has to be replaced with something. Just make sure the fat replacements you eat are natural and healthy.

How Low Is Too Low?

It's possible to eat a diet that is too low in fat. Since fats carry important nutrients and your body needs fat to function and maintain optimal health, a diet too low in fat can make you malnourished. A diet too low in fat will cause:

• Dry hair

• Dry skin

• Tiredness

• Eye problems

• Hair loss

• Pour wound healing

• Susceptibility to infection

• Signs of malnutrition

If your diet is too low in fat, you run the risk of becoming deficient in several critical vitamins. Vitamins A, D, K, and E are fat-soluble. That means they are carried by fat in food and stored in the fatty tissue in your body. Other nutrients, including vitamin C, are absorbed better by your body if they are accompanied by a small amount of fat. And then there are essential fatty acids. These compounds, which your body cannot make, must come from food. Essential fatty acids are used in tissue repair and cell function.

Some researchers think that no more than 10 percent of calories should come from fat. A diet that low in fat will cause weight loss, although the general effects are disputed. It is very difficult to maintain a diet that low in fat, because it's hard to make your body feel full.

How High Is Too High?

Eating a diet too high in fat — one in which you get more than the recommended 20 to 35 percent of your calories from fat — can lead to problems like weight gain. In its extreme, obesity, weight gain increases your risk for a multitude of health problems.

Put simply, eating too much fat makes it too easy to go over the amount of calories your body needs in a day. Those excess calories, whether from sugar, fat, or protein, will be stored in your cells as fat. And once there, it's difficult to get rid of fat and shrink those cells.

A recent study at the University of Minnesota shows that eating too much fat can damage your liver. Excess fat is stored in the liver; this can lead to metabolic syndrome, which causes insulin resistance and other health problems.