The key to weight management is incorporating three strategies into lifelong practices—eating healthfully, exercising regularly and, for some women, changing your relationship with food. Unfortunately, of the estimated 36 percent of Americans who are trying to lose weight, a minority use this method.

The most important key to success is to approach any changes in diet and exercise not as punishment, but as a plan to implement pleasurable healthy substitutes for unhealthy overeating and sedentary behavior.

Eating for Weight Management

Keeping in mind the biological reason we eat—to provide our bodies the energy and nutrients it needs to carry out the tasks we ask of it—is a good way to think about food.

Since an estimated 90 percent of dieters who lose weight regain all or part of it within five years indicates that "dieting" is not the answer to weight management. The best "diet" is a way of life that you can follow for the rest of your life. Therefore, it should consist of a balance of a variety of foods.

You can ask a nutritionist or registered dietitian for guidance on the number of calories you should eat to reach and maintain your goal weight. But as a rule of thumb, you should take in about 250 calories per day less than is needed to maintain your current weight and add an exercise regime that burns an additional 250 calories a day if you want to lose weight. This regimen should help you safely lose about a pound per week.

One simple method to estimate how many calories your body needs to maintain its basic functions—known as your basal metabolic rate—multiply your current weight by 10. (Men should multiply their weight by 11). For example, a woman who weighs 135 pounds requires 1,350 calories per day just to maintain bodily functions like breathing and digestion. You need additional calories to provide energy for daily activities like walking, vacuuming, even sitting at the computer.

It's difficult to determine exactly how many calories you need to maintain your weight at your current level of physical activity, however. One way is to take your basal metabolic rate and add about 20 percent if you're relatively sedentary, 30 percent if you're lightly active and 40 percent if you're moderately active. So a 135-pound woman who is lightly active needs about 1,755 calories a day to maintain her weight. If she needs to lose weight based on her height or body composition, she should then subtract 250 calories to arrive at her new recommended daily total of 1,505 (assuming she plans to add exercise).

A more accurate method is to keep a detailed food diary over a few days to a week during which you maintain your weight. Determine exactly how many calories you eat on an average day—several books and web sites provide calorie counts for thousands of different foods—and use that figure as a starting place for weight maintenance or weight loss.

After you've determined how many calories per day you should eat, plan daily menus. A registered dietitian or nutritionist can help you plan menus that include the types and amounts of food you should eat which, in most cases, should be based on the sensible guidelines set forth by the federal government in its Dietary Guidelines, which were updated in January 2005. The guidelines, available at http://www.healthierus.gov/dietaryguidelines, emphasize reducing calories, moderation and variety in food choices, with a special emphasis on consuming more whole grain products, vegetables and fruits.

The best and easiest advice to follow is to divide you plate into sections. Half your plate at main meals should consist of colorful vegetables, one quarter of grain products such as whole-grain bread, pasta, whole grain rice and cereals, and one quarter of meat, fish or poultry. Several times a week, you should substitute dishes made from dried beans or peas as your main course. You should also eat plenty of fruits and use low-fat milk products like yogurt as a side dish or a beverage three times each day.

These guidelines will help reduce your calories and fat and increase the amount of fiber in your diet, all of which has been shown to decrease the risk for heart disease. While you should try to cut back on fats and sugars, allow for an occasional treat. As soon as you label a food as "off limits," chances are you will crave and perhaps even binge on it. A few simple ways to cut back on calories include:

• Hold the sauce. Dishes that include high-fat sauces, mayonnaise and regular salad dressings should be consumed only occasionally and only in small portions.

• Drink more water. And steer clear of calories hidden in drinks like juice drinks, alcoholic beverages, fancy coffee concoctions and smoothies. Avoid excessive fruit juice consumption.

• Eat high-volume foods. High-volume, low-calorie foods, like most fruits and vegetables, are high in water and fiber, helping you feel fuller longer. Up your intake of vegetables and cut back on fats and sweets.

Health care professionals recommend women have moderate fat consumption, between 20 to 35 percent or less of your total calorie intake. Trans fat (also called trans fatty acids) and saturated fats should account for no more than ten percent of your intake, and you should get equal amounts of monounsaturated fats and polyunsaturated fats —that is, more vegetable-source fats. Also, reduce cholesterol intake to less than 300 mg per day.

Strategies for reducing saturated fat and cholesterol include:

• Only eat three servings or less per week of red meats, processed meats, organ meats, eggs and high-fat dairy products.

• Choose low saturated-fat protein sources, such as fish, turkey, chicken, legumes (dried peas and beans), nuts and seeds.

• Use lean cuts of meat and trim excess fat.

• Substitute skim and low-fat milk for high-fat dairy foods.

• Broil, bake or boil foods instead of frying.

• Increase your consumption of fruits, vegetables and whole grains.

You've probably heard of "good" fats and "bad" fats. These labels refer to the effects various types of fat have on your body and health. Saturated fats are commonly found in animal-based food products, as well as in palm and coconut oils. They are solid at room temperature. Excess amounts of saturated fat are considered unhealthy because they can cause fatty deposits in the arteries, clogging them and leading to heart disease. Unsaturated fats are liquid at room temperature and are known as oil. Two types of unsaturated fats are monounsaturated and polyunsaturated, both of which are thought to help lower cholesterol. Examples of these fats are olive and canola oils.

Trans fats are actually unsaturated fats that have been chemically modified. Manufacturers add hydrogen to vegetable oil in a process called hydrogenation. This increases the shelf life and the flavor stability of foods containing these fats. Trans fats can be found in vegetable shortenings, some margarines, crackers, cookies, snack foods and other foods made with or fried in partially hydrogenated oils. Like saturated fat and dietary cholesterol, they raise LDL cholesterol and increase your risk for cardiovascular disease.

Essential fatty acids are a category of fatty acids found in polyunsaturated fats your body needs but cannot manufacture itself. Good sources of one type, omega-3, include certain fish, flax seeds, pumpkin seeds and walnuts. Good sources of the other type, omega-6, include corn oil, sunflower oil and soybean oil.

When an unsaturated fat is solidified—into margarine, for example—the process turns it into partially hydrogenated oils, which contains trans fatty acids.

The Skinny On Fad Diets

Despite the ads that claim miracle weight-loss for some products, there simply is no magic formula for losing weight. Fad diets, like those based on cabbage soup, grapefruit or protein, may help you lose some pounds—often water weight—in the short run but they don't work in the long term because they're impossible and unhealthy to maintain. The truth is, permanent weight loss takes time and requires a permanent change in eating and exercise habits.

Extreme diets of less than 1,100 calories per day carry health risks and could trigger unhealthy binging or overeating following the period of extreme caloric restriction. Such diets usually provide insufficient vitamins and minerals as well. Severe dieting also has unpleasant side effects, including fatigue, intolerance to cold, hair loss, gallstone formation and menstrual irregularities. Most of the initial weight loss is in fluids; later, fat is lost, but so is muscle, which can account for more than 30 percent of the weight loss.

It is very dangerous to be on severe diets longer than 16 weeks or to fast for more than two or three days. There have been rare reports of death from heart arrhythmia when liquid formulas didn't have sufficient nutrients.

High-protein, low-carbohydrate diets have become popular again. Although a high-protein diet will lead to quick weight loss, its long-term health and safety benefits are uncertain. One byproduct of this type of diet is the release of substances called ketone bodies, which can lead to a condition called ketosis and cause nausea, and lightheadedness because you are restricting your body's source of fuel. Such high-protein diets may also be high in saturated fat and low in fiber-rich and healthful whole grains, fresh fruits and vegetables. They may also result in carbohydrate binges.

Carbohydrates provide your body with its main source of fuel and energy, namely, glucose. Simple and complex carbohydrates are stored in muscle and contain a lot of vitamins, minerals and fiber. Simple carbohydrates offer quick energy boosts, while complex carbohydrates provide the body with fuel for several hours.

Examples of simple carbohydrates include fruit sugars (fructose) found in fruits, milk sugars (lactose) found in milk products, and other forms of sugar found in sweeteners such as corn syrup, honey, dextrose, high-fructose corn syrup and fruit juice concentrates. Complex carbohydrates are found in whole grains, rice, dried beans and peas, such as lentils and black, kidney and pinto beans.

Carbohydrates stored in the body are packed with water. That's why introducing a low-carbohydrate diet leads to rapid weight loss as the body turns to stored carbohydrates for energy, eliminating large amounts of fluid from your body. After the stored carbohydrates are gone, your body turns to fat and lean body tissue for fuel, inducing further weight loss.

Many people on low-carbohydrate diets actually eat less but feel fuller due to the high-protein, high-fat foods they consume. However, this creates more work for your kidneys, which have to process the high amounts of protein. This is especially dangerous for people with diabetes. Additionally, excess protein excretion can cause valuable calcium to be excreted.

Many health care professionals believe that rather than adhere to a low-carbohydrate diet, it's healthier to consume healthy carbohydrates in reasonable amounts. This means focusing on complex carbohydrates like beans, whole grains, and vegetables, as well as simple carbohydrates that pack plenty of fiber, such as fruits.

Choosing A Diet Plan

With all of the fad diets circulating these days, you need to do your homework before embarking on a new weight-loss plan. The following questions will help you determine if a diet is healthy and legitimate or just a scam:

• Does the plan promise dramatic and rapid weight loss? If a program is promising results that sound too good to be true, they probably are. A 10-pound loss in two weeks is unrealistic and may also harm your overall health. A weight-loss goal of one to two pounds per week is a safe and effective rate for long-lasting results.

• Does the plan exclude entire groups of foods? If a weight-loss plan excludes an entire group of foods such as grains, fruits, vegetables, dairy or protein, you risk missing out on essential vitamins and minerals.

• Does the plan require extremely low calorie levels? Most experts agree that we need to consume at least 1,200 calories each day to maintain a healthy body. This is an absolute minimum; most people actually need more. If a weight-loss plan restricts calories below this level, it's not nutritionally adequate and you'll be in danger of nutrient deficiencies.

• Are you required to buy special foods or supplements to follow the program? Weight-loss programs that rely on special foods or supplements tend to be no more than money-making schemes to benefit the seller. These types of programs will drain your wallet without teaching you anything about nutrition and healthy eating habits.

• Does the plan address lifestyle changes, such as increased exercise and improved eating habits? Realistic weight-loss plans should focus on the causes of your weight gain, not just on short-term losses, but on long-term lifestyle changes.

• Can you continue this way of eating for the rest of your life? Weight loss is difficult, but maintaining that weight loss is even harder. Any plan that allows you to lose weight should also be a plan you can continue indefinitely, to maintain that weight.

The following claims and promotions should alert you to the probability of a bogus weight-loss scheme:

• The plan is touted as requiring no sacrifice—no exercise or no change in your eating habits.

• No reliable evidence or scientific proof is offered to back up claims that the plan is safe and effective; the promoter has not had the plan properly tested in clinical trials.

• Testimonials and case histories of people who have supposedly been successful on the plan are offered as "proof" of its effectiveness. A few successes don't prove the plan will work for everyone.

• The plan is described in sensational articles, or worse, advertisements made to look like articles, in tabloids and weight-loss magazines.

• The plan is promoted as "cleansing" the body of "toxins" to let the body's "natural" curative powers help in your weight loss efforts.

Today's most popular weight-loss programs vary greatly. No single diet is appropriate for each and every person, so you'll want to weigh factors that vary by plan, such as types of food you can eat, their reliance on supplements or drugs, calorie levels allotted and the amount of support they offer.

Popular Weight-Loss Plans

• Weight Watchers:

  This diet program, one of the most popular among health care professionals, has helped more than 25 million people worldwide lose unwanted pounds since it was founded in 1963. In general, the plan is healthy—long on fruits and vegetables and short on fat, protein and sugar. Weight Watchers provides member support through weekly weigh-in meetings. (Your weight is kept private.) Meeting leaders have achieved their own weight loss goals with Weight Watchers and have been able to maintain their goal weight. They are trained in leadership skills and must pass program tests and take continual training courses to maintain their leader status. The discussions can be helpful because they focus on the common challenges you face when trying to lose weight—what to do about eating in restaurants or at a wedding, for example. They also let members exchange dietary advice on tasty alternatives or ideas for cutting calories out of meals.

  Exercise is stressed as part of the program as well. In the past, the diet steered members toward a very healthy nutritional balance by outlining how much of specific food groups—fruits, vegetables, dairy products, protein, starches and fats—should make up their daily diets. However, in the past few years, Weight Watchers introduced a system that assigns point values to each food. Dieters are allowed to consume a specific number of points per day based on their weight and members aren't given as much direction about how to divide those points between the various food groups. As a result, a dieter on this program could eat too much of a single, and perhaps unhealthy types of food.

  A recent addition to the program is the "10 percent difference" that offers members a practical framework for focusing their weight-loss efforts. The program begins with assessing your current weight and determining your goal weight. However, rather than defining success as achieving your goal weight, you focus on achieving a 10 percent loss of your total body weight. After losing the 10 percent, the focus shifts to getting you to your goal weight. In this way, you gain the substantial health and self-esteem benefits of a 10-percent weight loss, as well as a motivation boost as you refocus on your overall goal. Weight Watchers does have a line of signature foods that can go along with the program, but the diet does not depend on these foods, and you can follow it with regular supermarket items.

• Nutri/System:

  This diet is based mostly on NutriSystem's prepackaged foods and involves reducing participants' calorie intake to an average minimum of 1,200 calories per day for women and 1,500 for men. The NutriSystem program is now completely at-home—participants have the option, however, to go online to chat with one of their weight loss counselors. Clients determine weekly goals with "diet technicians," often focusing on exercise. While the program was developed by registered dietitians and health educators, with input from physicians, there have been some complaints in the media that the diet technicians are not highly trained; if this is of concern to you, you may want to ask at your center and ask your health care professional.

  Because clients eat prepackaged meals, they have few food decisions to make. Thus they're not learning how to make choices in the real world or change their lifestyles. The program also sells vitamin/mineral supplements.

• Jenny Craig:

  This program also relies on its own brand of prepackaged foods, plus some additional supermarket foods, and provides from 1,000 to 2,600 calories daily, depending on your gender and current weight. Clients can attend weekly lifestyle classes and receive one-on-one counseling or choose an at-home program that allows for consultations via phone. As their comfort level grows, clients are given the option to transition to regular foods.

  Jenny Craig emphasizes increased physical activity, changing ingrained eating habits and learning how to balance meals and food choices. The program was developed by registered dietitians and psychologists with input from physicians.

  Relying on prepackaged foods makes dining out and socializing difficult and also de-emphasizes behavior modification and lifestyle change that are pertinent and very important to long-term weight loss. Also, Jenny Craig makes "weight-loss supplements" an integral part of the system. While vitamin/mineral supplements may be helpful to overall health, no herbal or enzymatic supplements should be relied upon for weight loss.

• Optifast:

  A medically supervised program of fortified liquid-meal replacements or prepackaged foods, Optifast eventually includes regular foods. Dieters are assigned 800, 950 or 1,200 calories daily and are seen regularly by a physician, a registered nurse, a registered dietitian and/or a psychologist, often in a hospital setting. Mandatory weekly sessions promote positive eating behaviors and one-on-one counseling is available.

  While the program itself discourages the use of diet drugs, some sites offer phentermine, a prescription weight-loss drug, based on the discretion of the individual physician. The program emphasizes changes in behavior and diet planning for "real" foods in group and individual counseling sessions, and exercise physiologists are available to help design personal exercise plans. But dieters must rely on Optifast products during the reducing phase, and it can be difficult to transition from liquid to regular food.

  Because of the close contact with health professionals, this program is beneficial for people with serious health problems (with the approval of their health care professional) who need a low-calorie plan to promote quick weight loss, which would then be followed by a real-food diet.

• Low-Carb Diets

  These trendy diets, including the Atkins, Sugar Busters and Protein Power plans, claim that carbohydrates—and not fat or an overindulgence in calories—are what make people gain weight. They go against the recommendations of the U.S. Department of Agriculture (USDA), the American Heart Association, the American Dietetic Association and the American Diabetes Association.

  Fat and protein intake are unlimited in some of these plans, more limited in others. The higher fat and protein level of the Atkins Diet can provide more fullness with meals and snacks. Foods containing simple carbohydrates are restricted, so blood sugar surges after a high-carbohydrate meal doesn't occur, also helping control appetite. This also prevents blood sugar levels from rapidly plummeting, which contributes to hunger.

  These diets rebel against the past decade's message for healthy eating—moderate fat, increase whole grains, fruits and vegetables and moderate amounts of protein. These recommendations were—and still are—based on scientific evidence that eating a well-balanced diet will decrease risks of chronic disease and increase health. While high-fiber diets rich in fruits and vegetables are shown consistently to decrease chronic diseases, diets high in animal protein continue to raise concern of possible increased risks for certain cancers.

  Some nutritionists are willing to accept that the low-fat craze may have gone too far, leading to the consumption of too much carbohydrates and added sugars. Healthier carbohydrates, like whole grains, should be emphasized over things like bagels and fat-free cookies, they say. However, most of them still agree that the high-protein, low-carbohydrate diets can be dangerous and unhealthy. In fact, an advisory published in the American Heart Association's (AHA) journal Circulation echoes several recent studies that found that high-protein diets have no proven effectiveness in long-term weight reduction and, according to the advisory's authors, may "pose health threats for those who adhere to them for more than a short time."

  Note: Because prolonged ketosis (a side effect of high-protein diets) can lead to kidney damage, people with a family history of renal disease or who have renal problems should avoid high-protein diets.

• The Zone:

  This diet relates excess weight to both overeating, and/or to unbalanced consumption of calories from the carbohydrate, fat and protein groups. In the Zone, your diet is exactly 40 percent carbohydrate, 30 percent fat and 30 percent protein. You must keep this ratio for all meals and snacks.

  Protein requirements are established by assessing your lean muscle mass and physical activity level. Your protein needs are then divided into blocks, with each block representing seven grams of protein. Having established the required number of protein blocks, you assign one carbohydrate block (nine grams complex carbs) and one fat block (one-and-a-half grams) for each protein block. Meals and snacks consist of an equal number of carbohydrate, protein and fat blocks. Compared to many other low-carb regimens, this diet promotes a higher percentage of low-fat protein foods.

  Simply put, this diet is most likely successful because it restricts caloric intake enough to lose weight. The average person eating in the Zone consumes no more than 800 to 1,200 calories a day. Some critics also consider this a strict, controlled eating regimen, requiring significant effort to adhere to a complex set of rules, charts and tables.

• Single-Food Diets

  Diets that push grapefruit or eggs, cabbage soup or oranges have surfaced over the years, some claiming a false connection to the Mayo Clinic or American Heart Association. These diets are dangerous because they're unbalanced nutritionally and rely on too few calories.

• Slim-Fast and Nestle Sweet Success:

  These liquid meal-replacements are milk-based products that have added vitamins and minerals. If "balanced" is defined as containing adequate amounts of the nutrients the government has established as the Reference Daily Intakes (RDIs) then Slim-Fast and Sweet Success meet the requirements. Slim-Fast recommends that users "replace, combine, dine—and snack." Replace breakfast with a Slim-Fast shake or meal bar, combine a shake or meal bar with 200 calories of a healthy food choice at lunch (i.e., 1/2 sandwich, soup and crackers), dine on a sensible meal at dinner (about 500 calories), and snack between meals on fruits and vegetables and calorie-controlled healthy snacks (based on your individualized meal plan).

  Recent research shows that meal replacement diet plans such as Slim-Fast really work. A landmark 10-year study demonstrated that the Slim-Fast Meal Replacement Plan not only helps individuals lose weight, but also helps maintain body weight long term. Participants weighed 33 pounds less after 10 years than a matched group.

  One thing that might stand in your way is hunger. Another drawback is that nutritionists recommend you divide your caloric intake evenly throughout the day, but on the Slim-Fast plan you may end up loading up on calories in the evening. In addition, if you stop following the Slim-Fast or Sweet Success plan and return to old habits, any lost weight returns.

  This is the same problem of any program that gives you a diet and doesn't teach you anything about the eating habits that led to the weight gain in the first place.

Using Medication to Lose Weight

Women with increased medical risk from their obesity may benefit from adding a weight-loss medication to their nutritional/exercise regimen.

Most research-based and professional associations recommend lifestyle therapy for at least six months before embarking on a weight-loss plan using physician-prescribed drug therapy. Even then, it must be used only as part of a comprehensive weight loss program that includes dietary therapy and physical activity. Currently available prescription medications include:

• Phentermine (Adipex-P, Fastin, Ionamin, Obenix, Oby-trim, Phentercot, Phentride, Pro-Fast, Teramine, Zantryl)

• Diethylpropion (Tenuate, Tepanil)

• Mazindol (Sanorex, Mazanor)

• Phendimetrazine (Adipost, Bontril, Melfiat, Obezine, Phendiet, Plegine, Prelu-2)

• Benzphetamine (Didrex)

• Sibutramine (Meridia)

• Orlistat (Xenical)

Most of these appetite suppressants have been approved for short-term use, meaning a few weeks or months. Sibutramine and orlistat are the only weight-loss medications approved for longer-term use in significantly obese patients, although their safety and effectiveness have not been established for use beyond two years.

Most of these drugs decrease appetite by affecting levels of certain brain neurotransmitters that affect appetite. Orlistat does not act directly on the central nervous system but instead blocks an enzyme essential to fat digestion so your body doesn't absorb fat. In general, combining weight loss medications with an increase in activity level and a decrease in calories can help you lose five to 10 percent of your body weight within a year.

If you are, may be or could become pregnant or are nursing, be sure to tell your health care professional. The effects of most of these drugs have not been tested on unborn babies; however, medications similar to some of the short-term appetite suppressants have been shown to cause birth defects when taken in high doses. Also, diethylpropion and benzphetamine pass into breast milk.

Before you take any product for weight loss, be sure to discuss it with your health care professional first. There are numerous potentially dangerous over-the-counter drugs and herbs that claim to help you lose weight. These drugs and herbs have not been approved by the FDA and may cause significant health complications and even death.

Trying To Gain Weight?

For the underweight woman who needs to gain weight, either for health reasons or appearance's sake, the journey can be difficult. Weight gain is much more difficult than losing weight. The underweight woman may have a higher metabolism, fewer fat cells or a genetic tendency to be leaner. She may also be taller, or just not care about food.

Winning at weight gain comes down to pairing a balanced eating pattern with regular physical activity—like any healthy lifestyle. The trick is to make sure you eat more calories than you burn. But you shouldn't give up exercise, as it has many health benefits! Consider adding a weight training program because building muscle will increase your weight. Here are some more tips that can help:

• Plan ahead for extra meals and snacks. Instead of the traditional three square meals a day, add two or three substantial snacks between three moderate-size meals. By spreading out your food choices during the day, you'll be more likely to enjoy your meals and snacks without feeling overstuffed.

• Concentrate on calories. Tip the scales toward weight gain by choosing foods that are calorie-dense, or high in calories. While rich desserts and fried foods quickly come to mind, the emphasis should be on foods that pack other nutrients, such as protein, vitamins and minerals, in addition to calories. These include dairy foods, nuts, peanut butter or avocados. Aim for the higher end of the recommended number of servings from each group in the Food Pyramid. And watch your use of added sugars and saturated and trans fats.

• Let snacks work in your favor. Smart snacking plays an important role in gaining weight. Choose snacks that add calories, vitamins and minerals, such as powdered milk added to a yogurt or ice cream-based shake with fruit and fruit juice, nuts and seeds. Dip crackers, chips and fresh vegetable relishes into high-calorie dips made with low-fat cheese, low-fat sour cream, mashed beans or salad dressings made with mono- or unsaturated oils. Space out snacks during the day so you don't spoil your appetite for later meals.

Physical Activity is Key to Weight Management

Daily physical activity is essential to weight management. Exercise not only burns calories, it also tempers your appetite, boosts metabolism, improves sleep and provides psychological benefits, such as an increased feeling of control and self esteem, as well as reducing stress.

If you are over 40, have been inactive for some time, suffer from shortness of breath or weakness that interferes with daily activities, or have a chronic health condition, consult a health care professional before increasing your physical activity. Notify your health care professional about any chest pain, faintness or dizziness, bone or joint pain you're experiencing, and any medications you're taking.

Physical activity is defined as any bodily movement produced by skeletal muscles resulting in energy expenditure. The best kinds of exercises for burning calories are moderate to vigorous intensity physical activities

Moderate intensity activities include:

• Hiking

• Light gardening/yard work

• Dancing

• Golf (walking and carrying the clubs)

• Bicycling (less than 10 mph)

• Walking (3.5 mph)

• Weight lifting ( general light workout)

• Stretching

Vigorous intensity physical activities include:

• Running/jogging (5 mph)

• Bicycling (more than 10 mph)

• Heavy yard work

• Weight lifting (vigorous effort)

• Basketball (vigorous)

While you and your health care professional should set up a detailed exercise plan based on your individual health status, the 2005 Dietary Guidelines recommend healthy women engage in 60 minutes of moderate-to-vigorous aerobic exercise on most or all days of the week .

You don't have to do 60 minutes at once; thirty minutes of an aerobics video in the morning and 30 minutes of brisk walking in the evening works just as well as walking for an hour straight.

The best way to keep weight off once it's been lost is with 60 to 90 minutes of moderate-intensity exercise most days, being careful not to exceed your specific daily calorie requirement.

If you have been inactive, you need to work up slowly to this amount so you don't get injured or overly fatigued and then become discouraged. Start with five or 10 minutes (or whatever you're comfortable with) every other day, adding one minute every other session. Low- to moderate-intensity physical activity, like housework, gardening and walking the dog provide a great deal of general health benefits, but for weight loss, you need to up the ante and exercise at a higher intensity with more vigorous activities like brisk walking or jogging, singles tennis/racket sports, aerobics classes, ice or roller skating, swimming or cycling.

Because the goal of moderate to vigorous physical activity is to work your heart muscle, your exercise needs to increase your heart rate. One way to determine if you are exercising intensely enough is to measure your heart rate. After warming up and then sustaining an aerobic activity for about five minutes, take your pulse by placing two fingers on the carotid artery on the side of your neck, just under your jaw line and about one to two inches in front of your ear. Count the beats for 10 seconds.

Your heart rate should be about 50 to 85 percent of its maximum, which is your age subtracted from 220.

If you're out of shape or older than 60, aim for an intensity at the lower end of the 50 to 85 percent range of your maximum heart rate. To determine what your heart rate should be during exercise, subtract your age from 220; divide that number by six for a 10-second heart rate count, then multiply that number by 0.5 for the lower end of the range and 0.85 for the higher end. For example, if you're 70:

• 220 - 70 = 150 (this would be your maximum heart rate for one minute)

• 150 ÷ 6 = 25 (this would be your maximum heart rate for 10 seconds)

• 25 x 0.50 = 12.5 (this would be 50 percent of your maximum, or the lower end of where your 10-second heart rate should be when you're exercising)

• 25 x 0.85 = 21.25 (this would be 85 percent of your maximum, or the higher end of where your 10-second heart rate should be when you're exercising).

The following chart illustrates recommended 10-second heart rate counts; the number of beats you count should fall between the two numbers listed beside your age.

An easier way to judge intensity is the "talk test." You shouldn't be exercising so hard that you can't talk with a friend or recite a poem. If you can't talk without gasping for breath, slow down. On the other hand, if your exercise is easy enough that you can sing a song out loud, you probably need to increase your intensity.

Another type of exercise has received much attention over the past several years for its contribution to weight loss efforts. Strength training -- which includes weight lifting and isometrics, or using your own body weight as resistance, not only improves muscular strength and endurance but raises metabolism, enabling you to burn more calories.

Make sure you take a few minutes to stretch and warm up before doing any kind of exercise.

It's best to incorporate a combination of both types of exercise into your lifestyle — moderate to vigorous physical activities to burn fat and strength training to build muscle. Neither is as effective alone.

At the same time, you need to reduce the amount of television you watch, since TV watching is independently associated with weight gain.

Some Techniques May Not Live Up to Expectations

Spot exercising, or training particular areas of your body, won't reduce body fat in specific locations because exercise draws on fat stores throughout your body. Gimmicky devices such as bust developers, vacuum pants and exercise belts do absolutely nothing to reduce fat in specific locations or, in the case of the bust developer, to add bulk. Electrical pads wrapped around the waist, arms or thighs have been reported to cause burns and fires. Similarly, cellulite-removal creams have been shown in several studies to be ineffective. Their apparent effect on fat may simply be from constricting blood vessels and forcing water from the skin, which could potentially be dangerous for people with circulation problems.

Liposuction is an increasingly popular technique to reduce fat in specific areas on the body. Liposuction, also called lipoplasty or suction lipectomy, is a surgical procedure that vacuums out fat from beneath the skin's surface to reduce fullness in areas such as the abdomen, hips, thighs, knees, buttocks, upper arms, chin, cheeks and neck. But depending on how much fat is removed, liposuction may not lead to weight loss, and it definitely won't change any behaviors associated with weight gain. It is also not an appropriate strategy for everyone, as age and skin tone can play a role in how successful the technique will be.

Get Your Mind In Gear

Another key to successful weight loss is incorporating behavioral strategies into your new eating and exercise activities. These include learning about nutrition, planning what to eat and making sure you eat regularly to end impulsive and thoughtless eating.

Some other specific and helpful behavioral strategies include:

• Set the right goals. Your goals should focus on specific dietary and exercise changes, such as "I will eat five servings of fruits and vegetables every day this week," or "I will work up to being able to walk briskly for 30 minutes at a time," rather than just on weight loss. Select two goals at a time to incorporate into your lifestyle rather than trying to change everything at once. Effective goals are specific, attainable and forgiving, which means that you don't have to be absolutely perfect. Remember, too, in your goal setting, that losing more than one to two pounds per week can be unhealthy and greatly improves your chances of gaining the weight back.

• Reward success. To encourage yourself to attain your goals, reward yourself for successes. An effective reward is something that is desirable and timely such as attending the cinema or taking an hour for yourself. Don't use food as a reward!

• Keep a food and exercise diary. Many behavioral psychologists believe it's necessary to track your daily food consumption to achieve long-term weight loss. From a simple pad of paper to a computerized program that provides reports and analyses of your progress, the best tool is the one you use every day. Incorporate your goals, such as eating five servings of fruits or vegetables each day, into your self-monitoring efforts.

• Monitor your weight sensibly. Keep track of your weight, but don't weigh too often. One day's diet and exercise patterns won't have a measurable effect on the scale the next day and your body's water weight can change from day to day, which may frustrate you and derail your efforts.

• Join a support group. Weekly meetings at a nearby support group or even over the Internet can help in a variety of ways. They provide accountability, helpful ideas, emotional support, an outlet for sharing frustrations and a variety of other psychological benefits.

• Use positive self-talk. Take responsibility and see yourself as in control, able to talk yourself into exercising every day rather than being angry, hopeless or in denial.

• Find ways other than food to respond to stress and other situations in your life. Certain cues, from stress to watching television, may stimulate unhealthy eating. In some cases, you can avoid those cues; don't go to that Mexican restaurant where you always eat too many chips, for example. For situations that can't be avoided, however, such as the business lunch or an argument with your spouse, relearn new ways to respond. If you track the situations surrounding your overeating in your food diary, you can more easily determine the cues you need to be aware of.

• Change the way you go about eating. There are a variety of tricks, from using a smaller plate to eating more slowly, that can help you eat less. Setting an eating schedule, starting meals with a broth-based soup, only buying foods on a pre-planned menu and other similar efforts can all help.

• When eating out, don't feel compelled to finish your entire meal if portion sizes are too large. The steady growth of food portion sizes served both in restaurants and at home has encouraged the overeating that is fueling the obesity epidemic in the U.S., according to a recent survey by the American Institute for Cancer Research.

• Appropriate portion size is very important. When dining out, for instance, try to take home at least half of your dish. When eating at home, serve your plate and leave the remaining food in the kitchen, do not place it on the table. Half your plate should be filled with vegetables, one quarter with a protein and one quarter with a starchy vegetable. Never, ever, supersize any kind of fast food or take out meal.