While it's possible to lose weight by changing your diet without exercising, you'll lose weight more quickly if your weight-loss plan includes diet and exercise, according to a study published in Obesity in 2012. The key to losing weight is to eat fewer calories than you burn during the day. You shouldn't expect to lose very much in just one week, especially if you're trying to lose weight through dieting alone. Aim for weight loss of 1 to 2 pounds weekly.

Weight Loss in 7 Days :

Each pound of fat contains about 3,500 calories, so eating 500 to 1,000 calories fewer than what is required to maintain your current weight will help you lose about 1 to 2 pounds per week. If you're a man, you need between 14 and 18 calories per pound to maintain your weight, depending on how active you are, and if you're a woman, you need between 12 and 16 calories per pound. Thus, a man who weighs 180 pounds and is sedentary needs about 2,520 calories per day to maintain his weight and about 2,020 calories per day to lose about 1 pound per week. A sedentary woman of the same weight needs about 2,160 calories to maintain her weight and 1,660 calories per day to lose about 1 pound per week.

You shouldn't try to lose more weight than that safe 1 to 2 pounds a week using diet alone, as eating too few calories can slow down your metabolism and make it even more difficult to lose weight. Men need to eat at least 1,800 calories per day, and women need to eat a minimum of 1,500 calories per day to prevent this potential decrease in metabolism.

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