BMI - Body Mass Index Calculator

(1)   What does your BMI Mean?

The Body Mass Index is designed to be a simple measure of obesity. According to the CDC,

(2)   BMI Formula, and its Limitations

The Body Mass Index is defined as

BMI = weight / height²

The obvious limitation of the BMI formula is that it doesn't distinguish between fat weight and (healthier) muscle weight. Bodybuilders and other athletes can easily have a BMI in the "overweight" range and in fact be extremely lean. More typically, sedantary people with little muscle tone can have a BMI in the "normal" range, but be what is known as skinny-fat.

(3)   Finding Your Ideal Weight

You can also run the formula backwards: given your height and desired BMI (defaulted here to a mid-range "normal" value of 22), you can find your ideal weight:

The same limitations still apply: the BMI formula can only give an approximate target weight for typical people.

(4)   Finding Required Calories

You can get a very rough estimate of the number of calories required to maintain a desired weight by multiplying weight (in pounds) by 12:

This is a minimum calorie requirement, corresponding to a fairly sedentary lifestyle. (In other words, this is how many calories your body burns every day just maintaining itself and doing simple chores, without you having to do any exercise.)

(5)   Calories and Weight Loss

One pound of body fat contains 3500 calories. That means that losing a pound of fat per week is pretty do-able: just maintain a daily caloric deficit of 500 calories (since 500 x 7 = 3500).

By contrast, one pound of muscle contains less than half as many calories. This explains the dirty little secret behind some fad diets: they make you lose muscle (and water) instead of fat. (Not good: you want to lose fat, not waste away.) So avoid the fads and burn the fat: healthy weight loss is a slow and steady process.

(6)   More...

EatThisMuch.com shows the calorie count and nutritional content of different foods:

Number of calories in:

Beyond counting calories, it helps to avoid spiking your blood sugar; that way you will burn calories instead of storing them. Insulin Resistant 1 and The Glucose Revolution have many useful videos. (Note that advice meant for type 2 diabetes can be very helpful for weight management. The takeaway: Avoid low fiber carbs, and move your muscles after meals.)

Accuracy of Body Mass Index to Diagnose Obesity In the US Adult Population from the NIH discusses the usefulness and limitations of the BMI. Figure 2.A shows the (rough and nonlinear, especially for women) correlation between BMI and body fat percent.