Weight Loss Diets

With over 50 percent of the population of the United States and other industrialized countries being either overweight or obese , a great number of people want to lose weight. However, weight loss is not easy—and not often successful.

Weight gain is a result of consumed energy in the form of high-calorie foods eaten in excess of the body's need for energy. An adult's body needs energy to provide for its physiological functions, including heart, kidney, and liver function; blood circulation; respiration; muscle tone; and constant body temperature, called basal metabolic rate (BMR), as well as the energy spent in physical activity. An adult woman who is moderately active needs about 2,000 calories per day to meet all her nutrient requirements and maintain a healthy weight. She must therefore choose her diet carefully, avoiding fast foods and any other high-fat, high-sugar foods, eating a variety of fruits, vegetables, and whole-grain foods, and exercising regularly to avoid depositing excess body fat.

When energy consumption exceeds energy expenditure, excess energy is stored as fat in the body. A person usually gains weight gradually, adding less than a pound per month depending on the level of physical activity and amount and type of food eaten. It is very unusual to gain weight suddenly or at a faster rate than one pound per week. To be successful, the weight loss must also be gradual. Weight loss of one to two pounds per week is recommended, accompanied by a nutrient-dense diet with adequate amounts of high-fiber, whole-grain foods, and exercise.

Eating too few calories may cause the loss of lean muscle tissue as the body withdraws glycogen stored in muscles to fuel the nervous system. The ideal weight-loss diet eliminates excess fat but not muscle, which requires moderate diet restriction and increased physical activity. [Photograph by Michael Keller. Corbis. Reproduced by permission.]
Eating too few calories may cause the loss of lean muscle tissue as the body withdraws glycogen stored in muscles to fuel the nervous system. The ideal weight-loss diet eliminates excess fat but not muscle, which requires moderate diet restriction and increased physical activity.
[Photograph by Michael Keller. Corbis. Reproduced by permission.]

In any weight loss attempt the goal is to lose the excess fat that has been accumulated in the body, rather than to lose weight. Therefore, strategies must be chosen carefully to achieve the goal of losing fat. Research has proven that the only long-term way to reduce body fat (and not body protein and water, which can be quick but ineffective) is to reduce the intake of high-fat and sugary foods and to exercise regularly. A successful weight loss diet must include adequate amounts of all essential nutrients that the body needs to maintain health. It is important to reduce the fat and concentrated carbohydrates (sugar, candy, high-fat and high-sugar desserts, fried foods, fatty meats, and whole-fat dairy products) in the diet, to reduce the intake of red meat and cheese as much as possible, and to avoid soft drinks (soda) and alcohol. However, if such a diet contains less than 1,600 calories per day, health will be compromised. It is also important to exercise regularly (at least thirty minutes per day, or more if the goal is to lose fat faster).

In spite of reports appearing in popular news magazines and newspapers on high-protein diets, scientific researchers in the field of nutrition believe that although high-protein diets may reduce food intake by inducing early satiety and increasing the thermic effect of foods temporarily, the long-term possibility of kidney problems, bone mineral loss, and other unknown long-term risk factors make these diets unsuitable for weight loss.

Losing weight at a rate of about one to two pounds per week is safe and doable. It takes a deficit of about 3,500 calories to lose a pound of weight, which can be accomplished in a week by cutting out 500 Kcalories per day. However, a young girl who eats 2,000 calories a day and cuts back to 1,500 calories per day may end up being deficient in iron and calcium . A better strategy would be to reduce calorie intake by 250 and burn the other 250 through exercise. That would equal about three miles of race walking or thirty minutes of bicycling each day. With this strategy, a very adequate, balanced, and normal diet can be followed—one that provides all the necessary nutrients. Individuals can vary the foods they eat without getting tired of "being on a diet." Developing a regular exercise habit will not only aid weight loss but will help a person feel better.

Fad Diets and Weight Cycling

Many fad diets promise fast weight loss with little effort. However, any program that offers quick and easy results must be viewed with suspicion. If there were any way to easily lose weight there would not be so many over-weight and obese people around. Many people fall for these promises and start to lose weight (not fat), but they soon become tired or give themselves a vacation from dieting and gain the lost weight back, plus some more. Remembering their initial weight loss, they then go back on the diet and lose some of the gained weight, but not all of it. Repeating this cycle several times they end up gaining weight because each time they went off the diet they gained a little more weight than what they had lost.

This practice is called "weight cycling" or "yo-yo dieting." As an individual starts reducing his or her food energy intake, body cells sense the reduced energy and nutrients and start economizing in terms of energy expenditure in BMR. Therefore, less heat is produced by the body and less involuntary activity and physiological functioning are performed. As soon as the individual resumes his or her pre diet food habit, more fat is deposited in the body, resulting in a faster rate of weight gain. Repeating this cycle a few times results in a net weight gain rather than weight loss. Under these conditions the body composition also changes, and the percentage of body fat is increased. This increases the risk of degenerative diseases such as obesity , type II diabetes , cardiovascular disease, hypertension , and cancer .

In order to avoid these problems, an individual interested in losing weight should follow these recommendations:

  • Do not believe or follow any of the fad diets that promise easy and quick weight loss, because there is no such thing.
  • Combine weight reduction programs with exercise, which not only utilizes more energy, but also increases lean body tissue (muscle fibers), which in turn increases BMR.
  • Make sure that one's diet is varied, adequate in all essential nutrients, and includes adequate numbers of servings of fruits, vegetables, and whole-grain products.
  • Try to lose body fat rather than body weight by following an exercise program that includes resistance training as well as aerobic activity.
  • Be patient and lose weight gradually. Remember, weight gain did not happen fast, and neither will weight loss.
  • Avoid weight cycling.

SEE ALSO Dieting ; Fad Diets ; Obesity ; Yo-Yo Dieting .

Simin B. Vaghefi


Eisenstein, J.; Roberts, S.; Dallal, G.; and Saltzman, E. (2002). "High-Protein Weight-Loss Diets: Are They Safe and Do They Work? A Review of the Experimental and Epidemiological Data." Nutrition Review 60:189–197.

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