Fat provides texture and flavor to food, making meals more enjoyable. When fat is severely limited in the diet, eating loses some of its pleasure and some people (who may be trying to lose weight) compensate by eating greater amounts of fat-free, carbohydrate-rich foods. Increased carbohydrate consumption causes hunger to return more quickly, leading to a diet that, while higher in overall energy, is much less nutritionally balanced.
Severely limiting fat often leads to eating more frequently to compensate, which in turn sometimes leads to binge eating.
Perhaps the most serious outcome of a severely limited fat intake is the effect it has as other nutrients are eliminated from the diet. Those on an overly restrictive diet typically suffer deficits in several important dietary components, such as calcium and iron.
Because fat contains 9 calories per gram, it provides considerably more energy than protein or carbohydrate, each of which yields only 4 calories per gram. In other words, our bodies get more than twice the energy from fat as they do from protein or carbohydrate. When total energy intake is low – which can easily occur with a very low fat or nonfat diet – individuals may simply lack the fuel necessary to build muscle mass and repair tissue.
Lack of energy is of special concern for those who exercise regularly. Despite frequent meals, these people may never feel full or satisfied and often lack sufficient energy to work out.
These essential fatty acids help manufacture hormones and nerve cells and are important for carrying and absorbing fat-soluble vitamins A, D, E and K.
Fat intake affects the rate at which the body absorbs nutrients. Consuming a moderate amount of fat will cause food to be absorbed more slowly, allowing energy to be released into the muscles gradually and consistently. For example, eating a bowl of nonfat cereal with skim milk for breakfast can leave you hungry within an hour or two. Yet simply adding a slice of toast spread with a little peanut butter (which adds fat as well as other important nutrients) can delay the food's absorption, helping you feel full longer.
Fat helps maintain healthy skin and hair; two of the telltale signs of a lack of fat in the diet are dry, brittle hair and scaly skin.
How much fat is right? If too little fat can be a problem and eating too much fat increases the risk of heart disease and other health related problems, what is a good middle ground for fat intake? A common recommendation is that an average person obtains 30% of total daily calories from fat, or 20-25% they have elevated cholesterol levels. For most people who exercise regularly, 20-25% is reasonable and would translate to 45-70gm of fat for active people consuming 2,000 to 2,500 calories daily.
How To Make Changes
More important than the exact amount of fat in the diet is determining whether the diet is balanced, and whether a person is comfortable eating an appropriate amount of fat. For someone eating virtually no added fat, gradually adding small amounts would be more appropriate than trying to immediately increase fat intake to 20%. Rapidly adding large amounts of fat to the diet could result in physical symptoms such as cramping, bloating and diarrhea, so gradual increases are crucial.
Focusing solely on the fat grams listed on the 'nutrition facts' labels makes it easy to ignore the protein requirements essential for health and strength. For example, because a bag of pretzels may be fat-free, people may eat a whole bag instead of a meal, taking in excess calories but not enough protein and other nutrients. There is a big difference between healthy eating and simply fat-free eating.
The transition away from a limited-fat diet will be easier if done in small, gradual steps to balance the diet. There is no right or wrong way to make these changes as long one understands the importance of fat in the diet and is willing to try different things. The following are practical ways people can gradually add fat back into the diet:
The ketogenic diet (a diet high in fat, low in carbohydrate and protein) has been in use and discussed in medical literature since the 1920s. It was replaced when the modern anticonvulsants became available, even though it has a very good success rate at controlling seizures. In some cases it is actually better than drugs at controlling seizures, having a success rate of 75%. Seizures are stopped in 50% of cases and reduced in 25%.
A ketogenic diet produces circulating ketones and a state called ketosis, where ketones are found in the urine. Ketones, like glucose, are burned for energy, but indicate that either fat is being taken from body fat stores or dietary fat intake is high. In attempting seizure control, this ketotic state exerts an anti-epileptic effect but its mechanism of action is not completely understood.
The ketogenic diet is used to treat intractable epilepsy in children. It may be prescribed when seizures are out of control, and when the side-effects of anticonvulsant drugs and/or surgery are considered unacceptable. The diet is safe, with rare side effects only when not strictly followed.
Most kids can stay on the diet for two years, get off it and never have another seizure again. The diet works best in children under the age of ten: they are less likely to cheat and young children can maintain ketosis better than adults or older children.
The diet mimics the effects of starvation. It has long been known that fasting has a beneficial effect on seizure control. Doctors at the Mayo Clinic came up with a way to induce the effects of starvation (fat burning, ketosis and a change in blood pH levels) by feeding the patient large quantities of fat and limiting protein and carbohydrate. The diet has to be rigidly controlled as any deviation can throw the patient out of ketosis and produce a seizure.
Most people investigate this diet as a last resort. The diet is unpalatable and demands great commitment from the entire family for a considerable period of time. The diet is deficient in many vitamins and in calcium, so a good (carbohydrate-free) vitamin supplement is important.
For those interested in more information, The Ketogenic Diet: A Treatment for Epilepsy by J. Freeman (2000) is often recommended.