To lose weight, you need to burn more calories with physical activity than you take in by eating and drinking. The total number of calories you consume minus the total number of calories burned is your net calories. The lower your net calories are every day, the more weight you will lose.
Determining Net Calories
Keep track of the calories you consume by using an online calculator or a food diary. You must know what foods and beverages you eat or drink and the amounts you consume to get an accurate calorie count. Your calories burned is equal to your basal metabolic rate, or BMR, and your activity level. You can use an online calculator to determine how many calories you burn each day. Subtract the amount of calories you burn from the calories you consume to determine your net calories.
Understanding Net Calories
If your daily net calories equal zero, you are burning the same number of calories you are taking in, so you maintain your current weight as long as you continue at this rate every day. If your net calories is more that zero, you will gain weight over time, and if your net calories is consistently a negative number, you will lose weight.
One pound of fat is equal to 3,500 calories, so you'll need to reduce your calories by 500 each day to lose one pound per week. You can eat less food or choose foods that are lower in calories. You can also increase your physical activity, or do a combination of reducing your caloric intake and increasing your burn. The National Institute of Diabetes and Digestive and Kidney diseases says you should avoid fad diets, which promise fast and unrealistic weight loss.
See your doctor for a physical examination before you start a diet and exercise program. You may also want to see a dietitian who can help you set up a diet that will decrease your caloric intake while providing the proper amounts of carbohydrates, fats, protein, fiber, vitamins and minerals your body needs. Do not eat fewer than 1,000 calories per day without the supervision of your doctor, as per the Weight-Control Information Network. Very low-calorie diets can cause adverse health conditions such as fatigue, nausea, diarrhea and gallstones.