Cutting down the number of calories you consume in a day is the cornerstone of losing excess weight. As a rough rule of thumb, here is how calories translate to weight:
- One pound of fat equals about 3,500 calories. Therefore, one could lose a pound a week by cutting about 500 calories a day. Naturally, the more calories you cut, the faster the weight loss. However, very-low calorie diets have been associated with some serious health consequences. (See below.)
- To determine your own personal daily calorie requirement, multiply the number of pounds of your target (ideal) weight by 12 - 15 calories. This gives a range that lets you adjust for gender, age, and activity levels. For instance, a 50-year old woman who wants to maintain a weight of 135 pounds and be mildly active might require only 12 calories per pound (1,620 calories a day). A 25-year old female athlete who wants to maintain the same weight might require 25 calories per pound (2,025 calories a day).
Warning on extreme diets
Extreme diets of less than 1,100 calories per day carry health risks and are often followed by bingeing or overeating and a return to an obese state. Such diets often have insufficient vitamins and minerals, which must then be taken as supplements. Most of the initial weight loss is in fluids. Later, fat is lost, but so is muscle, which can account for more than 30% of the weight loss.
No one should be on severe diets longer than 16 weeks or fast for more than 2 or 3 days. Severe dieting has unpleasant side effects, including fatigue, dizziness, intolerance to cold, hair loss, gallstone formation, and menstrual irregularities. There have been rare reports of death from heart arrhythmias when liquid formulas did not have sufficient nutrients. Those whose diets include a high intake of fluids and much reduced protein and sodium are at risk for hyponatremia (low sodium), which can cause fatigue, confusion, dizziness, seizures, and in extreme cases, coma.
Jeffrey Heit, MD, Internist with special emphasis on preventive health, fitness and nutrition, Philadelphia VA Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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