500-Calorie Diet

Vegetables and olive oil

Are you considering a 500 calorie diet for fast weight loss? Before you do, it is important to know the facts about dieting, weight loss, and calorie restricted diets.

Losing Weight

If you are overweight, then losing weight can help reduce the risk of certain diseases such as heart disease and diabetes. Most physicians consider one to two pounds per week to be a safe rate of weight loss. Losing weight more rapidly may result in loss of lean tissue rather than body fat, which can lead to a weakened immune system, loss of bone density, and a decreased metabolism.

Low-Calorie Diets

Many health care professionals recommend eating a calorie-reduced diet in order to lose weight. By eating fewer calories than you burn, you create a caloric deficit, and your body seeks energy from stored fuel, which may include body fat and lean tissue. One pound of weight equals roughly 3,200 calories, so if you create a 3,200 calorie deficit via diet and exercise, you will lose a pound. If you generate a 3,200 calorie excess, you will gain one pound.

How Many Calories Do You Need?

Every body is different, and a number of factors contribute to how many calories you need to maintain your current weight. Factors include:

  • Sex
  • Age
  • Current body weight
  • Activity level

Additionally, hormonal factors may play a role in caloric needs.

Basal Metabolic Rate

In order to determine how many calories your body needs just to perform the functions of daily life, such as respiration and circulation, you can calculate your basal metabolic rate. This is the amount of calories needed to maintain your current weight, if you stay in bed all day. You may use a BMR calculator to determine your body's basic caloric requirements.

Activity Level

Next, determine how your activity level affects your daily caloric requirements. To do so, utilize the Harris-Benedict equation, which is a multiplier that factors how active you are. The number you receive supplies the number of calories you need to eat at your current activity level to maintain your present weight.

Putting it All Together

In order to better understand, look at an example. Suppose you have a sedentary 35 year old woman who currently weighs 185 pounds, and is 5'6" tall. That woman's BMR is 1,605 calories per day to sustain bodily function. At a sedentary activity level, she can eat 1,926 calories per day to maintain her present weight of 185 pounds. If she would like to lose one to two pounds a week, she needs to create a caloric deficit of between 3,200 and 6,400 calories per week. That means each day, she needs to eat between 457 and 914 calories fewer than the amount required to maintain her current weight. Therefore, that dieter should eat between 1,012 and 1,469 calories each day in order to lose one to two pounds per week if she does not alter her activity level.

500 Calorie Diet

While diets at low as 500 calories per day are recommended for some obese patients when weight loss is critical for health reasons, such low-calorie diets are not recommended for anyone unless the dieter is monitored by a medical professional.

Eating a 500 calorie diet falls well below anyone's basal metabolic rate. Eating this little food each day can lead to many side effects including:

  • Weakness
  • Bone and lean tissue loss
  • Inadequate nutrition
  • Exhaustion
  • Decreased immune function
  • Slowed metabolism
  • Hunger
  • Irritability

Mental Factors

In 1944, Ancel Keys and other researchers at the University of Minnesota conducted the Minnesota Starvation Experiment to test the effects of long-term semi-starvation on humans. During the period of semi-starvation, participants were given 1,560 calories per day for 12 weeks. During that time, participants experienced a host of psychological and mental disorders, including preoccupation with food, depression, decline in comprehension and concentration, decrease in metabolic rate, and reduced body temperature.


The USDA created the Food Pyramid to help you choose healthy foods that provide for your body's nutritional needs. You need vitamins and minerals, as well as protein, carbohydrates, and fats to sustain healthy bodily function. When you significantly decrease your caloric intake, you do not provide your body with adequate nutrition, leading to nutritional deficiencies and illness. Five hundred calories per day does not allow adequate nutrition.

Since a 500-calorie per day diet can influence you negatively on both a physical and mental plane, opting to eat such a diet is most likely unhealthy. If you do choose to follow an extremely low-calorie diet that falls below 1200 calories per day, do so only under the direct supervision of a doctor.

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