A pound of body fat is equal to approximately 3,500 calories. If you have a daily calorie deficit of 500 calories less than you’re basal metabolic rate (how many calories you burn in a day) you would lose approximately one pound per week (500 calories x 7 days = 3,500 calories). You can create this 500 calorie deficit by either restricting your food intake or by burning calories with exercise. It’s always best to try to hit it from both ends, so eat 250 calories less and also burn 250 calories working out. This way, your body will be properly fueled during the day and keep your metabolism humming along. Restricting calories too low will cause muscle tissue loss which is the last thing you want, since muscle tissue is the most active tissue in your body and is critical for burning calories and keeping you lean.