Weight loss - intentional

Alternative names
Losing weight; Dieting - fad diets; Fad diets

To successfully lose weight, you must carry out a plan to balance your caloric intake with exercise. Ideally, dieting should be done by eating a nutritionally balanced, low-calorie diet and increasing physical activity.


The terms overweight and obese describe excess body weight. Overweight typically refers to weight 10% above the expected body weight for height and build. Obese refers to being 20% over the target. The greater the excess, the more significant the health risk.

Your health care provider has chart and tables that are used to determine what your target weight should be. They vary according to gender, height, age, and bone structure.

A simpler and more useful piece of information is Body Mass Index (BMI). The BMI is calculated by dividing your weight (in kilograms) by the square of your height (in meters).

To obtain your weight in kilograms, simply multiply your weight in lbs by 0.45. To obtain your height in meters, first multiply your height in inches by 2.5, then divide that number by 100. Don’t forget to square that result when you use it in the equation.

To fall within the “healthy range” on the BMI, your result should be within 20 and 25. Results both smaller and greater than these values are associated with significant health risks.

Another important piece of information is your percentage of body fat. This can be determined by a registered dietitian or an exercise physiologist. Using an instrument called a caliper, the thickness of a fold of skin is measured (for example, on the back of the arm) to estimate your total body fat. The average adult woman of normal weight in the United States may have 20-30% body fat. Adult men in the United States average 10-20% body fat. Athletes usually have less, pregnant women usually have more.


Although there are many programs advertised to help lose weight, the only proven long-term and safe method is to burn more calories than you consume.

This is achieved either by reducing the caloric intake (eat less food or healthier food) or by increasing the energy expenditure (exercise more). Often, behavior modification techniques like eating smaller portions are also used to help control eating habits. Once the weight is lost, these habits can be modified slightly for weight maintenance.

If you have unintentional weight loss, it can be a symptom of various medical or psychiatric disorders, or it can be from increasing your exercise or decreasing your food intake.


The U.S. Committee on Dietary Allowance has published recommended energy intakes for various age and sex groups. For example, a 20 year-old women who weighs 128 lbs needs 2,200 calories every day to maintain her weight.

This value would be increased if she were pregnant or nursing a child, and it would be decreased if she were trying to lose weight. The tables containing these values are available through nutritionists and online.


One pound of fat contains approximately 3,500 calories, so to lose one pound a week, a person should consume approximately 3,500 fewer calories per week. This can be done by reducing the daily intake by 500 calories per day (500 x 7 days will provide a deficit of 3,500 calories per week). To lose 2 pounds per week, a deficit of 1,000 calories per day is required.

If this seems impossible, remember that physical activity also contributes significantly to weight loss. The deficit of 500 to 1,000 calories can come from a combination of increased physical activity and reduced intake on a daily basis.

Therefore, you don’t need to experience significant food deprivation. The lowest intake per day recommended for females is 1,200 calories, unless they are in a medically-supervised, very low-calorie regimen which may have a daily level of 500 to 800 calories per day.

The lowest level recommended for males is 1,500 calories per day. A very low-calorie diet can also be used by males if they are in a medically-supervised program.

Here are some steps for weight maintenance and weight loss:

  • Increase your daily activity - take the stairs rather than the elevator, or walk rather than drive when possible.  
  • Reduce your food intake gradually. This will help make these new eating habits lifetime changes. Reduce fat intake on a daily basis, and reduce intake of other high-calorie foods.  
  • Change any habits that make you eat more, or eat poorly.  
  • Learn about the calorie content of foods and the calorie expenditure of various physical activities.


For weight loss to be successful, here is a summary of basic guidelines:

  • Aerobic physical activity will assist in increasing muscle tissue which will burn more calories. You should plan on 20-minute sessions at least 3 times per week.  
  • Gradual changes in eating habits will help encourage a permanent lifestyle change.  
  • A slow weight loss of 1 or 2 pounds a week, until the desirable body weight is reached, is best.


A registered dietitian is an excellent resource for individualized weight loss. Dietitians can provide information on classes and programs available in the community.

By far, the most well-known, community-based support group is Weight Watchers. Members meet every week and learn about healthy eating while encouraging each other in their weight loss goals.

Consumer brochures can be obtained from the Federal Trade Commission on evaluation of commercial weight loss programs.


A fad diet is one that makes unrealistic promises. Most fad diets are very low in carbohydrates and in calories, causing fluid loss from the body, which indicates a loss of weight on the scale. Once the body gets rehydrated with water, the weight will come right back on.

Evaluation of a fad diet:

  • Is the diet medically and nutritionally safe? Get an opinion from a physician and a registered dietitian.  
  • Red flags for fad diets include: overemphasis on a specific food group or groups, limited food choices, and a “calories do not count” approach.

These are ways to decide whether to use a diet or not. If there is no nutritionally or medically reliable information provided, and if there are no statistics to back the claims, then it is not a good diet to consider. Remember, if it sounds too good to be true, then it probably is.

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

Medical Encyclopedia

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0-9

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.