Extreme weight loss can pose many health risks. A healthy loss in fat occurs with a gradual reduction in calories. A study published in the June 2010 volume of the "International Journal of Obesity" found that, for overweight individuals, weight loss greater than 15 percent of body mass was associated with an increased risk of death.

Energy Balance

The only way the body is capable of losing weight is to burn more calories than it takes in, reaching a negative energy balance. You can get this negative energy balance by restricting your caloric intake or burning more calories through exercise. Eating smaller, more frequent meals can also speed up your metabolism and help you burn the calories you consume more quickly.

Rate of Fat Loss

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A negative energy balance of 3,500 calories will result in a 1.1- to 2.2-lb. loss of fat, according to the book "Essentials of Strength Training and Conditioning" by Thomas R. Baechle and Roger R. Earle. The maximum rate at which the body can lose fat is about 1 percent of body mass a week, which is reached by a 500 to 1,000 daily caloric deficit. For example. a 110-pound female can expect to lose exactly 1.1 pounds each week if she limits her caloric intake by 500 calories a day.

Considerations

Attempting to achieve a negative energy balance greater than 500 to 1,000 calories a day is associated with dehydration and nutrient deficiency, warn Baechle and Earle. It is also nearly impossible to lose weight that quickly without also losing muscle mass, rather than body fat. Therefore, gradual weight loss is much healthier than extreme fasting.

Diet Tips

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If your goal is to lose weight as quickly as possible, make sure to drink plenty of fluids to prevent dehydration and eat a balanced diet to avoid a vitamin and mineral deficiency. A low-fat diet can help you lose weight, but at least 20 percent of your calories should come from fat. Foods with low calories per volume, such as potatoes, soup and vegetables can help you lose weight while preventing feelings of hunger.