Body Mass Index & Fat

Body mass index, or BMI, is a measure of how much fat you have on your body. BMI uses a formula that compares your weight to your height to decide if you are overweight or have too much fat. Though it is a good rough measure, BMI does have some limitations.

BMI Basics

BMI is a number that helps quantify the level of fat in your body. Calculating BMI is basic math; you compare your height to your weight. The Mayo Clinic and The Centers for Disease control and Prevention both feature BMI calculators. You enter weight and height as well as your gender to quickly calculate your BMI index. According to the Centers for Disease Control and Prevention, a BMI between 18.5 and 24.9 falls within the "normal" range. BMI numbers below 18.5 mean you are underweight, and numbers above 24.9 mean you are overweight.

Muscle Mass and BMI

BMI is accurate for average individuals, but you might fall outside the norm. When you participate in sports and build muscle mass, your athletic physique might register as "overweight" on a body mass index. Muscle tissue weighs more than fatty tissue, so inch for inch, you weigh more if you have more lean muscle mass than if you do not.

Fat and BMI

Low or normal body mass index might mislead you. Fat tissue weighs less than muscle tissue, so when you do not exercise at all, and have a low weight, you might have an "underweight" or "normal" body mass index but still have unhealthy levels of fat in your body. Building a healthy balance might means increasing muscles through weight-resistance exercise and reducing fat levels by moderate calorie reduction.

Burning Fat

Burning body fat is the goal when you diet. Ideally, you maintain muscle mass while getting rid of adipose tissue. Keeping your metabolism levels high during diets requires you to reduce calories moderately and to participate in moderate exercise. The Centers for Disease Control and Prevention recommends that you get at least 30 minutes of moderately intense cardiovascular exercise five times a week or 150 minutes total per week.

Considerations

Check with a physician if you have concerns about fat levels in your body, or about any pre-existing health conditions, particularly in the abdominal area. Body mass index is a good indicator of fat levels, but the size of your waist compared to your hips and chest also is significant. Thicker waists in both women and men indicate an increased risk of obesity, diabetes and heart and circulatory problems in the future.