Body mass index, a measurement calculated using height and weight, is often used to help determine if someone is overweight, underweight or at a healthy weight.

Many things play a role in a person's body composition, including gender, diet, fitness level, genetics and activity level. When evaluating body fat, it is important to remember that it's not only high levels of fat that can be a risk, but also levels that are too low.

For the average 18-year-old female, the bicacromial or shoulder width is about 14 inches or 35 cm. For comparison, the average biacromial width is about 15 inches or 39 cm. for males of the same age.

Body mass index, or BMI, is a good guideline for keeping track of your weight. Your BMI value can tell you if you are underweight, less than 18.5; healthy weight, 18.5 to 24.9; overweight, 25 to 29.9; or obese, 30 to 39.9.

Maintaining a healthy weight isn't just about aesthetics; being overweight significantly increases your risk of various chronic diseases. One of the ways health providers indirectly measure body fat is by calculating your body mass index, or BMI.

A week gives you time to start the process of fat loss and even lose a pound or two. Losing a significant amount of body fat in seven days, though, isn't possible. Your body metabolizes fat over time to cause changes in your body composition.

Concurrently gaining muscle and losing fat is no easy feat, but can be done with the right exercise and eating routine. When you consistently strength train and increase your protein intake as you cut calories, you create an environment in which your body builds muscle as you shred excess fat.

"Ideal" is almost impossible to define when it comes to a man's weight. A healthy "ideal" could be very different than the "ideal" weight that adorns a fitness magazine cover. Weight also varies according to height and body shape.

A waist size greater than 40 inches indicates a man is at a high risk of type-2 diabetes and heart disease. This inflated, firm belly is due to an overabundance of visceral fat, which lies deep inside your trunk nestled around internal organs.

If you struggle to lose every ounce -- and seem to gain it all back by simply looking at a cheeseburger -- you know the power of a slow metabolism. Your metabolic rate depends on a few factors within your control, such as your activity level, but factors outside your control can play a role, too.

Your body composition is more important than the numbers on a scale. There are plenty of reasons to want to drop body fat percentage quickly. A couple of the most motivating factors are a sleeker appearance and decreased health risks.

The body mass index, or BMI, a formula derived from your height and weight, is the dominant indicator in the medical community of a healthy weight. BMI has its critics, though, because it doesn’t account for waist girth or age.