While fad diets come and go, the key to weight loss is to consume fewer calories than your body burns. Determining how many calories you should eat when dieting requires that you consider your activity level, age and weight to determine how many calories your body burns each day. Once you know this number, you can calculate how low you should go. While cutting more calories may help you to drop weight faster, it can also result in a lower metabolism and a weight loss plateau, according to the Columbia University Health Services.
A calorie is a unit of energy derived from food. Your body uses calories for all physical processes, ranging from movement to breathing. Eating fewer calories than you use will cause you to lose weight as your body relies upon stored fat instead of food consumed. A 3,500-calorie deficit will create a 1 lb. weight loss.
Before you can determine how many calories you should eat when dieting, you need to figure out how many calories you need in a day. Start by using a BMR calculator to determine your basal metabolic rate or how many calories your body uses at rest. Use a calculator that factors in your daily activity level for the most accurate estimation, like the one at the Prevent Disease website.
While fad diets suggest eliminating certain foods, your body does not distinguish between types of calories, regardless of the source. Often, extreme diets work simply because they produce an overall reduction in calories, rather than because of any food combining or reduction in one type of food or another. Cutting calories may be easier if you eat low-fat, low-calorie foods, but you will lose weight if you eat fewer calories than you burn, regardless of your food choices.
For most women, a 1,200 to 1,800 calorie a day diet will produce weight loss; however, if you start at a higher weight, you may need more calories to maintain your metabolism. Columbia University Health Services reports that diets below 1,200 calories a day may slow the metabolism, cause temporary infertility, impair thyroid function and lead to a weakened immune system. Very low calorie diets should only be undertaken with close medical supervision and only in cases of obesity with a BMI above 30.
Slow and steady weight loss of 1 lb. to 2 lbs. per week is ideal. A calorie deficit of 3,500 to 7,000 calories per week will produce this rate of weight loss; however, you can create that deficit with a combination of exercise and diet. Cut 500 to 750 calories from your basal metabolic rate calorie total per day, along with regular exercise, to lose weight.