There are many approaches to dieting and many claims for great success with various fad diets. To date, although many diets achieve effective immediate weight loss, none has emerged as an effective tool for maintaining healthy weight. The only definite recommendation that can be made about any diet plan is to be sure it includes an exercise program, assuming there are no health problems to forbid it.
The original food pyramid, with four food groups, has been replaced with an updated food guide called "My Pyramid." This illustrates the relative proportions of different foods that make up a nutritious, well-balanced diet and includes exercise.
Calorie restriction has been the cornerstone of obesity treatment. The standard dietary recommendations for losing weight are as follows:
- As a rough rule of thumb, one pound of body fat is the result of eating about 3,500 calories. A person could lose a pound a week by reducing daily caloric intake by about 500 calories a day. Naturally, the more severe the daily calorie restriction, the faster the weight loss. Very-low calorie diets have also been associated with better success, but extreme diets can have some serious health consequences.
- To determine your daily calories requirements, multiply the number of pounds of ideal weight by 12 - 15 calories. The number of calories per pound depends on gender, age, and activity levels. For instance, a 50-year old woman who wants to maintain a weight of 135 pounds and is mildly active might require only 12 calories per pound (1,620 calories a day). A 25-year old female athlete who wants to maintain the same weight might need 25 calories per pound 2,025 (calories a day).
- Fat intake should be no more than 30% of total calories. Most fats should be in the form of monounsaturated fats (such as olive oil). Saturated fats (found in animal products) should be avoided.
Warning on Extreme Diets
Extreme diets of fewer than 1,100 calories carry health risks. They are also often followed by bingeing or overeating, and a return to obesity. Such diets often do not have enough vitamins and minerals, which must then be taken as supplements. Most of the initial weight loss is in fluids. Later, fat is lost, but so is muscle, which can account for more than 30% of the weight loss. No one should be on very strict diets for longer than 16 weeks, or fast for weight loss. Severe dieting has unpleasant side effects, including fatigue, intolerance to cold, hair loss, gallstone formation, and menstrual irregularities. There have been rare reports of death from heart arrhythmias when liquid formulas did not have sufficient nutrients. Pregnant women who excessively diet during the first trimester put their unborn children at risk for birth defects. Of note, those whose diets include a high intake of fluids and much reduced protein and sodium are at risk for hyponatremia, which can cause fatigue, confusion, dizziness, and in extreme cases, coma and death.
Low-Fat and High-Fiber Diets
This dietary approach requires counting only grams of fat with the goal of achieving 30% or fewer calories from fat. One gram of fat contains nine calories, while one gram of carbohydrates or protein has only four calories. Fat in your diet converts more readily to fat in the body, compared with carbohydrates or proteins. Simply switching to low-fat or skimmed dairy products may be enough for some people.
There are possible drawbacks to this approach:
- Some people who reduce their fat intake severely may not get enough basic nutrients, including vitamins A and E, folic acid, calcium, iron, and zinc. People on low-fat diets should eat a wide variety of foods and take a multivitamin supplement, if appropriate. Calcium deficiencies may be particularly harmful in women at risk for osteoporosis.
- Many people start eating foods with too many carbohydrates, believing that they are not adding calories. No one should use a low-fat diet as an excuse for eating too many carbohydrates, particularly starchy foods and sugar. A high-calorie diet from any source will add pounds.
- Replacing fatty foods, such as cakes, cookies, and chips, with their commercial "low-fat" counterparts does not constitute a low-fat diet. These foods generally contain more sugar and hence more calories, not to mention other ingredients that have virtually no nutritional value.
- Very low-fat diets may increase the risk for stroke from hemorrhage in the brain.
Some fat in a diet is essential. It should come from plant oils and fish, however, and not from animal products or hardened oils, such as margarine. Trans fatty acids, found in hardened oils, are actually more of a risk factor for obesity than saturated fats from animal products, although both should be avoided.
Fiber and Complex Carbohydrates. In all cases, complex carbohydrates found in whole grains and vegetables are preferred over those found in starch-heavy foods, such as pastas, white-flour products, and potatoes. Fiber is an important component of many complex carbohydrates. Fiber is found only in plants, particularly vegetables, fruits, whole grains, nuts, and legumes (beans and peas). One exception is chitosan, a dietary fiber made from shellfish skeletons. Fiber cannot be digested but passes through the intestines, drawing water with it, and is eliminated as part of feces content. The following are specific advantages from high-fiber diets (up to 55 grams a day):
- Insoluble fiber (found in wheat bran, whole grains, seeds, nuts, and fruit and vegetable peels) has been associated with weight loss. Studies also suggest that diets rich in fiber from whole grains reduce the risk for type 2 diabetes.
- Soluble fiber (found in dried beans, oat bran, barley, apples, and citrus fruits) has important benefits for the heart, particularly for achieving healthy cholesterol levels and possibly benefiting blood pressure as well. Simply adding breakfast cereal to a diet appears to reduce cholesterol levels. People who increase their levels of soluble fiber should also increase water and fluid intake.
Low carbohydrate diets generally restrict the amount of carbohydrates but do not restrict protein sources.
The Atkins diet restricts complex carbohydrates in vegetables and, particularly, fruits that are known to protect against heart disease. The Atkins diet can also cause excessive calcium excretion in the urine, which increases the risk for kidney stones and osteoporosis.
"Low-Carb" diets, such as South Beach, The Zone, and Sugar Busters, rely on a concept called the "glycemic index," or GI, which ranks foods by how fast and how high they cause blood sugar levels to rise. Foods on the lowest end of the index take longer to digest. Slow digestion wards off hunger pains. It also helps stabilize insulin levels. Foods high on the glycemic index include bread, white potatoes, and pasta, while low-glycemic foods include whole grains, fruit, lentils, and soybeans.
There has been debate about whether Atkins and other low-carbohydrate diets can increase the risk for heart disease, as people who follow these diets tend to eat more animal-saturated fat and protein and less fruits and vegetables. In general, these diets appear to lower triglyceride levels and raise HDL ("good") cholesterol levels. Total cholesterol and LDL ("bad") cholesterol levels tend to remain stable or possibly increase somewhat. However, large studies have not found an increased risk for heart disease, at least in the short term. In fact, some studies indicate that these diets may help lower blood pressure.
Low-carbohydrate diets help with weight loss in the short term, possibly better than diets that allow normal amounts of carbohydrates and restrict fats. However, overall, there is not good evidence showing long-term efficacy for these diets. Likewise, long-term safety and other possible health effects are still a concern, especially since these diets restrict healthy foods such as fruit, vegetables, and grains while not restricting saturated fats.
Fat and Sugar Substitutes
Replacing fats and sugars with substitutes may help many people who have trouble maintaining weight.
Fat Substitutes. Fat substitutes added to commercial foods or used in baking deliver some of the desirable qualities of fat, but they do not add as many calories. They cannot be eaten in unlimited amounts, however, and are considered most useful for helping keep down total calorie count.
Olestra (Olean) passes through the body without leaving behind any calories from fat. Studies suggest that it helps improve cholesterol levels and may help overweight people lose weight. Early reports of cramps and diarrhea after eating food containing olestra have not proven to be significant. Of greater concern is the fact that even small amounts of olestra deplete the body of certain vitamins and nutrients that may help protect against serious diseases, including cancer. The FDA requires that the missing vitamins, but not other nutrients, be added back to olestra products.
Beta-glucan is a soluble fiber found in oats and barley. Products using this substance (Nu-Trim) may reduce cholesterol and have additional health benefits.
A number of other fat-replacers are also available. Although studies to date have not shown any significant adverse health effects, their effect on weight control is uncertain, since many of the products containing them may be high in sugar. People who learn to cook using foods naturally lacking or low in fat eventually lose their taste for high-fat diets, something that may not be true for those using fat substitutes.
Artificial Sweeteners. Many artificial or low-calories sweeteners are available. It should be noted that using these artificial sweeteners should not give dieters a license to increase their fat intake. There is some public concern about chemicals used to produce many of these sweeteners, and the side effects seen in studies using rats. Natural low-calories sweeteners are available that may be more acceptable to many people.
- Saccharin (Sugar Twin, Sweet'N Low, Sucaryl, and Featherweight). Saccharin has been used for years. Some studies found that large amounts of saccharin cause bladder cancer in rats. However, the rats were fed huge amounts that do not apply to human diets. Currently there is no evidence that saccharin causes cancer in humans.
- Aspartame (Nutra-Sweet, Equal, and NutraTase). Aspartame has come under scrutiny because of rare reports of nervous system disorders, including headaches or dizziness, associated with its use. People with phenylketonuria (PKU), a genetic condition, should not use it. Studies have not reported any serious health dangers in otherwise healthy individuals, but some people may be sensitive to aspartame.
- Sucralose (Splenda). Sucralose has no bitter aftertaste and works well in baking, unlike other artificial sweeteners. It is made from real sugar by replacing part of the sugar with chlorine. Some people are concerned because chlorinated molecules used in major industrial chemicals have been associated with cancer and birth defects. Over 100 studies have been conducted on sucralose over a 20-year period, with no reports of such risks.
- Acesulfame-potassium (Sweet One, SwissSweet, and Sunette). It has been used in the U.S. since 1988 with no reported side effects.
- Neotame (Neotame). Neotame is a synthetic variation of aspartame, developed to avoid its side effects. The association with aspartame has raised some concerns. Studies to date have reported no effects that would cause alarm, and it appears to be safe for general consumption.
- D-tagatose (Tagatose). This reduced-calorie sweetener is made from lactose, which is the sugar found in dairy products and other foods. It may be especially beneficial for people with type 2 diabetes. It may also have additional benefits that help the intestinal tract.
- Alitame (Aclame) is formed from amino acids, the building blocks of proteins. It has the potential to be used in all products that contain sugar, including baked goods.
- Stevioside (Stevia). This is a natural sweetener derived from a South American plant. It is available in health food stores. People with diabetes should avoid alcohol-based forms. It has not been carefully tested.
Other sugar substitutes being investigated include glycyrrhizin (derived from licorice) and dihycrochalcone (derived from citrus fruits).
Liquid Meal Replacements
Some studies have reported good success with meal replacement beverages (such as Slim-Fast and Sweet Success). They contain major nutrients needed for daily requirements. Each serving typically contains 200 - 250 calories and replaces one meal. (Note: Using them for all meals reduces calories to a severe extent and can be harmful.)
One study reported that most subjects who had undergone a 12-week weight loss program followed by using Ultra Slim Fast supplements as directed for maintenance kept off more than half their weight loss after more than 3 years. A quarter of the subjects were still losing weight.
Magnesium and Diet
Some evidence suggests that a diet rich in magnesium could reduce a person's risk of metabolic syndrome, a cluster of problems that include obesity, high blood pressure, and high cholesterol. Metabolic syndrome can lead to diabetes and heart disease. Epidemiological studies have found that the risk for metabolic syndrome decreases in those who consume the highest amounts of magnesium from meals.