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Weight control and diet

Description

An in-depth report on losing and managing weight safely for health benefits.

Alternative Names

Dieting; Obesity; Weight loss

Weight Management

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 to include an exercise program, assuming there are no health problems to preclude it.

The original food pyramid, with four food groups, has been replaced with an update 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

Calorie restriction has been the cornerstone of obesity treatment. The standard dietary recommendations for losing weight are the following:

As a rough rule of thumb, one pound of fat equals 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 the daily calories requirements for specific individuals, multiply the number of pounds of ideal weight by 12 to 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 require 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 less than 1,100 calories carry health risks and are often followed by bingeing or overeating and a return to the obese state. Such diets often have insufficient 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 severe diets longer than 16 weeks or fast for more than two or three days. 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.

Low-Fat and High-Fiber Diets

Some studies suggest that replacing foods high in fats with low-fat complex carbohydrates (fruits, vegetables, and whole grains) may be more effective than calorie counting, particularly in maintaining weight loss. 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, and dietary fat converts more readily to fat in the body than carbohydrates or proteins.) Simply switching to low-fat or skimmed diary products may be sufficient for some people.

There are possible drawbacks to this approach:

Some people who reduce their fat intake may not consume enough basic nutrients, including vitamins A and E, folic acid, calcium, iron, and zinc. People on low-fat diets should consume a wide variety of foods and take a multivitamin if appropriate. Calcium deficiencies may be particularly harmful in women at risk for osteoporosis.
Many people over-increase their intake of carbohydrates, believing that they are not adding calories. No one should use a low-fat diet as an excuse for over-consuming 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 calories, not to mention other ingredients, which have virtually no nutritional value. In fact, a 2002 study suggested that increasing sugar may, over time, reduce levels of HDL cholesterol, the so-called good cholesterol.
Very low-fat diets may increase the risk for stroke from hemorrhage in the brain.

Some fat in a diet is essential. It should be derived from plant oils and fish, however, and not from saturated fat from animal products or trans-fatty acids from hydrogenated (hardened) oils. (Trans-fatty acids, in fact, are more of a risk factor for obesity than saturated fats, 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 almost always 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, citrus fruits, and potatoes) 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.

High-Protein, Low-Carb Diets

High-protein, low carbohydrate diets such as the Atkins and South Beach diets have been touted as effective ways to produce short-term weight loss. Because of their emphasis on fats and proteins, many experts are concerned about long-term health problems. A report in the March 2006 Lancet linked the Atkins diet to life-threatening complications that caused the death of one woman. The 40-year-old woman had a deadly build up of acids called ketones in her blood, a condition called ketoacidosis. Ketoacidosis can cause coma. Ketones are a known by-product of high protein, low carb diet. At low levels they can cause nausea, lightheadedness, and bad breath.

Long-term effects on health are still unknown in people who use these diets long term. For example, the Atkins diet restricts some vegetables and most fruits that are known to protect against serious diseases such as heart problems and cancer. The diet also may cause too much calcium to build up in the urine. This can increase the risk for kidney stones and osteoporosis. In any case, high-protein intake, particularly from meat, can be harmful in people with kidney problems. Individuals at risk for kidney stones or who have other kidney problems should not go on high-protein diets without consulting their physicians. Unfortunately, many people with diabetes are subject to kidney problems, which could negate any possible benefits for them. A high meat intake has also been associated with certain common cancers, notably prostate and colon cancers. A 2002 study suggested that such diets during pregnancy may increase the risk for high blood pressure in the offspring.

Still, significant studies say that such diets improve on cholesterol and blood sugar levels. Studies in 2002 and 2003 have indicated that the diet lowers blood glucose levels, which can be important in people who are diabetic. The diet also reduces triglycerides (unhealthy fat molecules) and increases HDL (so-called good cholesterol) levels. High triglyceride and low HDL levels are important risk factors for heart disease and common in people with type 2 diabetes. Studies are mixed on whether the diet reduces overall cholesterol or LDL (the bad) cholesterol.

Experts that promote the low carb approach argue that heart problems from obesity are due to insulin disturbances from sugar imbalances. Therefore, they believe that restricting carbohydrates is the best approach for obesity--and especially for overweight people with diabetes. More research is needed, however, to determine the long-term impact on health.

High-protein, low-carbohydrate diets include Atkins, Protein Power, Sugar Busters, and Dr. Stillman. The Atkins diet is one of the most popular and has a four-phase program:

Induction. For the first 2 weeks, individuals consume no more than 20 grams of carbohydrates a day. The diet consists of pure protein and fats. There is no fruit, bread, grains, starchy vegetables, or dairy products other than cheese, cream, or butter. This phase is not suitable for children, pregnant women, or anyone with kidney disease.
On-going Weight Loss. After the first phase, individuals continue to lose weight while they increase carbohydrate levels by five grams each week.
Premaintenance. When individuals get close to their weight goal, they add another 10 grams of carbohydrates per week as long as they do not begin to gain weight. Weight loss is very slow at this time, but the individual is now getting used to maintenance.
Maintenance. Lifetime maintenance is usually between 40 and 100 grams of carbohydrates a week, depending on steady weight level.

Anyone who chooses this diet should prefer fish or soy products to meat as protein sources. Fish may reduce leptin, a hormone associated with fat storage and heart diseases, and would be the best protein source. People on this diet should also choose monounsaturated fats (as in olive oil) over saturated fats or trans-fatty acids fat. Patients often need supplements, at least a multivitamin and possibly calcium, chromium, omega-3 fatty acids (found in fish oil), and other supplements.

The South Beach and Zone diets encourage healthy fats. They also allow certain carbohydrates. For example the Zone uses healthy carbohydrates (vegetables and dried beans) and unsaturated fats. The South Beach diet uses carbohydrates that have a lower impact on blood sugar levels. This is called a low-glycemic index. Low-glycemic foods include barley, dried bean and peas, milk, strawberries, and apples. High-glycemic foods include refined grains, white bread, white potatoes, and bananas and other tropical fruits. The glycemic index was developed for use in diabetes--not for weight loss. Nevertheless, there is some evidence that foods with low glycemic indexes may produce a feeling of fullness and so discourage further eating. As with any high-protein diets, people at risk for kidney stones or have other kidney problems should avoid these plans.

Fat and Sugar Substitutes

Replacing fats and sugars with substitutes may help many people who have trouble maintaining weight. In fact, in one 2003 study, people with type 2 diabetes used the artificial sweetener sucralose and a beta-glucan fat substitute (derived from oats) as part of a low-calorie diet. At the end of the 4 weeks, they achieved better weight, glucose control, and HDL levels than those on a standard diabetic diet.

Fat Substitutes. Fat substitutes added to commercial foods or used in baking, deliver some of the desirable qualities of fat, but do not add as many calories. It should be stressed that eliminating all fats from a diet can be harmful to general health. Some include the following:

Stanols. Stanols are plant compounds used in margarines (Benecol, Take Control). Benecol is derived from pine bark and Take Control from soybeans. Two servings a day of either brand as part of a low-fat diet can lower LDL and total cholesterol by impairing its absorption in the intestinal tract. Some studies have reported that their use can allow lower doses of statins--cholesterol lowering agents. These products do not appear to block absorption of fat-soluble nutrients or vitamins, as olestra does. They can be hydrogenated, however, and so can contain some trans-fatty acids.
Olestra (Olean) passes through the body without leaving behind any calories from fat. Studies suggest that it improves cholesterol levels and helps people lose weight when it is used to replace a third of normal dietary fats. (Simply adding snacks containing olestra do not appear to have any effect on cholesterol or weight loss.) 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 be added back to olestra products, but not other nutrients. The side health effects, if any, are unknown.
Beta-glucan is a soluble fiber found in oats and barley. Products using this substance (e.g., Nu-Trim) may reduce cholesterol and have additional health benefits.

A number of other fat-substitutes are also available. Although studies to date are not showing any significant side health effects, their effect on weight control is uncertain, since many of the products containing them may be high in sugar.

Artificial Sweeteners. Many artificial or low-calories sweeteners are available. A 2002 study confirmed that people who consumed artificial sweeteners in beverages and foods and reduced their sugar intake weighed less over time than those who ate similar types and amounts of drinks and food containing sugar. It should be noted that using these artificial sweeteners should not give dieters a license to increase their fat intake. Studies indicate that consuming some sugar is not a significant contributor to weight gain as long as the total caloric intake is under control. There is some public concern about chemicals used to produce many of these sweeteners and side effects 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. Although the rats were fed huge amounts that do not apply to human diets, some evidence suggests that people who have six or more servings of saccharin per day may have an increased risk.
Aspartame (Nutra-Sweet, Equal, NutraTase). Aspartame has come under scrutiny because of rare reports of neurologic disorders, including headaches or dizziness, associated with its use. People with phenylketonuria (PKU), a rare genetic condition, should not use it. Studies have not reported any serious health dangers, but some people may be sensitive to it.
Sucralose (Splenda). Sucralose has no bitter aftertaste and works well in baking, unlike other artificial sweeteners. It is made from real sugar by replacing hydroxyl atoms with chlorine atoms. 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, 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 but was 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 is a reduced calorie sweetener is a novel low-calorie sweetener derived from lactose, which is found in dairy products and other foods. It may be specifically beneficial for people with type 2 diabetes and have additional benefits that aid the intestinal tract.
Alitame (Aclame) is formed from amino acids. 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 rigorously tested.

Others 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 (Slim-Fast, Sweet Success). They contain major nutrients needed for daily requirements. Each serving typically contains between 200 to 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 and then used 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

Medical evidence suggests that a diet rich in magnesium could reduce a person’s risk of metabolic syndrome, a cluster of problems including obesity, high blood pressure, and cholesterol. Metabolic syndrome can lead to diabetes and heart disease. A long-term study of thousands of Americans found that the risk for metabolic syndrome decreased in those who consumed the most magnesium from meals. The findings were published in the journal Circulation .

Support Groups and Behavioral Approaches

Commercial and Non-Profit Support Programs for Weight Loss. There are many different types of weight-loss program. (This report cannot address all of the many commercial and nonprofit weight-loss programs currently available, nor can it assess their claims.)

Taking off Pounds Sensibly (TOPS), a nonprofit support organization with many local chapters, is one of the least expensive programs, costing $20 a year.

Most of the commercial programs such as Weight Watchers, Jenny Craig, and NutriSystem offer individual or group support, lifestyle changes and packaged meals. These programs tend to be expensive. There are few well-conducted studies on these programs. One 2003 study reported modest weight loss over 2 years with Weight Watchers compared to a self-help program. There were no differences in heart risk factors.

Cognitive Behavioral Approaches. Most support programs use some form of cognitive-behavioral methods to change the daily patterns associated with eating. They are very useful for preventing relapse after initial weight loss. The following is a typical approach may work as follows:

The patient first records in a diary all activity related to eating patterns, including the times of day, length of meal, emotional states, companions, and, of course, the kind and amounts of food eaten. (Most people--even professional dieticians according to one study -- tend to underreport their daily calorie intake, but it is still a good method for increasing their awareness of eating patterns.) One patient said that recording circumstances surrounding relapses was a particularly valuable guide for understanding the stresses leading to her own eating behaviors.
The patient reviews the diary with a therapist or group to set realistic goals and identify patterns that the patient can change. For instance, if food is normally eaten while watching television, then the patient may be advised to eat in another room instead.
Good eating habits are reinforced by rewards, other pleasures that substitute for high calorie consumption and sedentary activities.

Behavioral modification has been shown to be helpful particularly for people who have an overly strong response to the taste, smell, and appearance of food. It also may be useful for binge eaters.

Stress-Reduction Techniques. Stress reduction and relaxation techniques may be helpful for some people with obesity, such as those whose weight is related to night-eating syndrome. [See In-Depth Report #31 Stress .]

Changing Sedentary Habits and Exercise

Changing Sedentary Habits. Making even small changes in physical activity can expend energy. For example, simply getting up to turn on and off the TV instead of using the remote and standing while talking on the phone may drop up to five pounds a year. Other suggestions include cooking one’s own food (instead of eating take out or fast food), walking to as many places as possible, using stairs instead of escalators or elevators, and gardening. Even fidgeting may be helpful in keeping pounds off, and, in one study, chewing gum increased energy expenditure. No one should rely on such mild activities, however, for serious weight loss. Only high levels of physical activity -- not just using up energy -- help prevent obesity.

Approach to Exercise. Exercise, which replaces fat with muscle, is the critical companion for any weight control program. In a one-year study, women who regularly averaged 3.5 days (176 minutes) of exercise each week lost significantly more weight than women who did not exercise regularly. Women who exercised more than 195 minutes a week lost nearly 7% of their abdominal fat.

People who exercise are more apt to stay on a diet plan. Exercise improves psychological well-being and replaces sedentary habits that usually lead to snacking. Exercise may even act as a mild appetite suppressant. Moreover, exercise improves overall health even with modest weight loss. In support of this, a British study found that overweight fit individuals had half the death rate of unfit trim individuals.

Be forewarned, however, that the pounds won’t melt off magically. Losing significant weight requires both intensive exercise and calorie restriction. In addition, if a person exercises but doesn't diet any actual pounds lost may be minimal because dense and heavier muscle mass replaces fat. Nonetheless, regardless of weight loss, a fit body will look more toned and be healthier. In addition, exercise benefits the heart even with modest weight loss.

The following are some suggestions and observations on exercise and weight loss:

The more strenuous the exercise, the better the chances for short- and long-term success. With intense exercise, the metabolism continues to burn calories before returning to its resting level. This state of elevated metabolism can last for as little as a few minutes after light exercise to as long as several hours after prolonged or heavy exercise.
The treadmill burns the most calories of standard aerobic machines. It may be particularly effective when used in short multiple bouts during the day. In fact, exercise sessions as short as 10 minutes in duration that are done frequently (about four times a day) may be the most successful program for obese people.
Resistance, or strength, training is excellent for replacing fat with muscles. It should be performed two or three times a week.
As people slim down, their initial level of physical activity becomes easier and they burn fewer calories per mile of walking or jogging. The rate of weight loss slows down, sometimes discouragingly so, after an initial dramatic head start using diet and exercise combinations. People should be aware of this phenomenon and keep adding to their daily exercise regimen.
As people age, they also need to exercise more to keep off the same amount of weight.
Changes in fat and muscle distribution may differ between men and women as they exercise. Men tend to lose abdominal fat (which lowers their risk for heart disease faster than reducing general body fat). Exercise, however, does not appear to have the same effect on weight distribution in women. In one interesting study women who underwent aerobic and strength training lost fat in their arms and trunk, but did not gain muscle tissue in these regions. On the other hand, they gained muscles but achieved no change in fat mass in their legs.

Warning Note. Because obesity is one of the risk factors for heart disease and diabetes, anyone who is overweight must discuss their exercise program with a physician before starting. Sudden strenuous exercise, in such cases, can be very dangerous.[See In-Depth Report #29 Exercise .]

Related Resources

University of Maryland Center of Weight Management and Wellness
Weight loss plan by Readers Digest

Review Date: 3/29/2006
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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