Taken from http://www.scientificpsychic.com/fitness/diet.html

What do the numbers mean?

* Body Mass Index (BMI) - The BMI is the ratio of your weight to the square of your height. The number is proportional to your body shape. Generally, the number is small for thin people and large for fat people. People with a BMI 25 or greater are considered overweight, unless they have a very muscular body. The BMI does not consider the fat/muscle ratio, and a healthy, muscular individual with a low percentage of body fat may be classified obese using the BMI formula. This is a well-known deficiency of the BMI formula. If your BMI is 25 or greater, and your Waist-to-Height ratio is less than 0.5 and your Percent Body Fat is in the "athlete" or "fitness" category, you are probably muscular and not fat.

Underweight BMI less than 18.5
Normal weight BMI 18.5 to 24.9
Overweight BMI 25 to 29.9
Obese BMI 30 or greater

Ronnie Coleman
BMI=36.6 BMI=41.4
BMI does not take into consideration how the weight is distributed.

* Waist-to-Height Ratio - The Waist-to-Height ratio is determined by dividing the waist circumference by the height. Waist-to-Height ratios of 0.5 or greater are indicative of intra-abdominal fat for both men and women and are associated with a greater risk of cardiovascular disease. A study found that persons with a normal BMI but a large waist circumference, corresponding approximately to a Waist-to-Height ratio of 0.55, had a 20% higher mortality risk than persons with a normal waist size.[7]

* Percent Body Fat - The percent body fat is calculated using the formulas developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. The formulas require the measurements to be in centimeters with an accuracy of 0.5 cm. However, the form above has been adjusted to accept measurements in inches. Men and women require different methods for measuring because men accumulate fat mostly in the abdomen (the "apple" body shape or "beer belly"), while women accumulate fat in their abdomen and hips (the "pear" body shape). The equations take this into consideration.
The formula for men is:
%Fat=495/(1.0324-0.19077(log(waist-neck))+0.15456(log(height)))-450

The formula for women is:
%Fat=495/(1.29579-0.35004(log(waist+hip-neck))+0.22100(log(height)))-450

The American Council on Exercise uses the following categories based on percentage of body fat:
Women Men
Essential fat 10-12% 2-4%
Athletes 14-20% 6-13%
Fitness 21-24% 14-17%
Acceptable 25-31% 18-25%
Obese 32% or more 26% or more

* Lean Body Mass - This is derived by subtracting the calculated value of body fat from the total weight.
Lean Body Mass = Weight × (100 - %BodyFat)

* Calories per day - The minimum number of Calories per day is calculated based on height and sex according to the guidelines of the Institute of Medicine. When the BMI is 25 or greater, the minimum number of Calories is reduced by 15% to obtain a diet that is not very severe and can be maintained for many months without adverse effects by persons with normal health. The number of Calories may need to be increased depending on the level of activity, but increasing them by more than 15% may not result in loss of weight. To lose weight, your intake of carbohydrates should be less than 60 grams per day (no more than 240 Calories) distributed throughout the day.

* Grams of protein per day - This value is calculated from the maximum normal BMI, your height, and your level of activity. It corresponds to 0.8 grams of protein per Kilogram of body weight which is the Recommended Dietary Allowance (RDA) for low levels of activity, 1.1 grams for moderate activity, and 1.4 grams for vigorous activity. Other components of the diet, including essential fatty acids and carbohydrates should be proportioned to provide the minimum required Calories per day. For men and women of equal height the caloric requirements are lower for women, but the protein requirements are the same for both men and women. This means that, in general, women's diets should be richer in protein than men's diets. Any diet should always include at least the minimum amount of protein to prevent loss of muscle tissue when the caloric intake is reduced. A typical high-protein diet would derive 30% of the Calories from protein, 30% from fat, and 40% from carbohydrate. A low carbohydrate weight-loss diet generally derives 25% of the Calories from protein, 65% from fat, and 10% from carbohydrate. The tables below show that these percentages provide more than the minimum protein requirement for 2000- and 1800-calorie diets. The U.S. Government Recommended Diet is used as the basis for the "% Daily Values" that are listed on the "Nutrition Facts" labels in food products.

High-Protein diet
Protein Fat Carbohydrate
Calories 30% 30% 40%
2000 600 Cal 600 Cal 800 Cal
150 g 67 g 200 g

Low Carbohydrate Weight-loss Diet
Protein Fat Carbohydrate
Calories 25% 65% 10%
2000 500 Cal 1300 Cal 200 Cal
125 g 144 g 50 g

1800 450 Cal 1170 Cal 180 Cal
113 g 130 g 45 g

U.S. Government Recommended Diet
Protein Fat Carbohydrate
Calories 15% 30% 55%
2000 300 Cal 600 Cal 1100 Cal
75 g 67 g 275 g