No matter how many fad diets come out with claims of allowing you to eat whatever you want in whatever amounts, if it violates the principles of basic metabolism, you will not lose weight. Simply stated, if you consume more calories than you expend through your body's natural requirements and exercise, you will not lose weight. The basics of good nutrition are balancing the number of calories you consume with the number of calories you burn. If you consume more calories than you burn your body will turn the excess calories to fat. If you burn more than you consume, your body will burn the extra required calories from your fat stores and you will lose weight. If your calories consumed and burned are in balance, your weight will be maintained.
The first step in understanding calories is to determine how many calories you need daily. The number of calories you need depends primarily on your activity level. The average male requires about 2,800 calories while athletes can burn up to four or even five thousand.
The three basic levels of activity into which most people fall into are:
Sedentary: This level is defined as little or no exercise a day. Males and this level need about 2,400 calories and females need 2,000.
Active: This level is defined as 30-60 minutes of exercise a day. Males and this level need about 2,800 calories and females need 2,200.
Very Active: This level is defined as more than 60 minutes of exercise a day. Males and this level need about 3,000 calories and females need 2,400.
To get truly accurate measurements of your daily caloric requirements, you can use a tool called the Harris Benedict Formula (HBF). The HBF uses your weight, age, height, and sex to calculate you basal metabolic rate (BMR), which is defined as the amount of calories you would burn if you slept all day long. Then by multiplying your BMR by your activity level, you can get a more accurate reading of your daily caloric needs. The HBF uses the metric system so remember to convert pounds to kilograms and inches to centimeters. You can do this by multiplying pounds by 0.4536 and inches by 2.54.
The first step in using the Harris Benedict Formula is to calculate your BMR:
For men: BMR= 66 (13.7 x weight in kg) (5x height in cm) - (6.8 x age in years)
For women: BMR= 655 (9.6 x weight in kg) (1.8 x height in cm) - (4.7 x age in years)
Once you've calculated your BMR, simply multiply it by your activity level.
Sedentary: BMR x 1.2
Active: BMR x 1.55
Very Active: BMR x 1.725
Once you've calculated how many calories you need you can adjust your caloric intake with your weight management goal. If you want to lose weight comfortably, aim for 500 less calories a day. One pound of fat is 3,500 calories so by creating a daily negative caloric balance of 500 calories you can burn off a pound of fat a week. So that's the science behind any weight loss plan but adhering to the plan is the challenge. A night of binging can ruin days of effort so try to get a partner to keep you in check and plan out your daily meals in advance.