Healthy Living

Most body composition analyses divide body composition into two components: body fat and lean body mass. We'll start with body fat. A certain amount of body fat, about 3% of total body weight, is necessary to sustain normal body functions, aptly dubbed essential fat. Women have an additional 9-12% essential fat that is considered sex-specific, and is associated with normal sex hormone functioning. Dropping below 3% body fat for men or 9-12% for women is considered unhealthy and can be dangerous or even life-threatening.

What is a healthy amount of body fat? This depends on who you are and what you do. Athletes on strict training and diet regimens may have as little as 14-18% body fat for women and 6-12% for men. The healthy, fit range is from 18-22% for women and from 12-17% for men. Having over 30% body fat for women and 20% body fat for men increases the risk of disease and is considered obese. If your body fat percentage is higher than the healthy, fit levels yet is lower than the obese levels, you may benefit from a healthy diet and exercise, but are not at health risk related to body composition.

Now that we've covered the basics on body fat, let's move on to what's left, which is collectively termed "lean body mass." Lean body mass includes everything in your body but fat - muscle, bones, organs, fluids, etc. By exercising regularly and eating a healthy, balanced diet, it is possible to achieve and maintain a desirable ratio of fat to lean. Resistance training can increase muscle mass, which thereby increases your lean body mass. And since your muscles are what gives your body shape and form over your skeleton, building strong, healthy muscles can make you look good, too!

Another benefit of increasing lean body mass is that it can help your body become a better calorie-burning machine! It's true - by increasing muscle mass, you will increase your resting metabolic rate (RMR) and burn more calories all day long! How is this possible? Because muscle tissue contains little organelles called mitochondria, which put simply, are little energy producing machines. The more muscle tissue you have, the more mitochondria you have. And yes - you've got it - the more mitochondria you have, the more calories you burn!

Fat cells, on the other hand, do not have any such amazing abilities. In fact, body fat above the level of essential fat is considered storage fat and is actually a source of fuel that can feed the mitochondria and help keep your body running. A certain amount of storage fat is also important for cushioning and protecting the bones, muscles and organs, and for temperature regulation. However, high levels of body fat can adversely affect temperature regulation, as well as overtax the body's organs and systems over time.

A last point to note is that your body weight is about 60-70% water, with muscle tissue being 70-75% water and fat 10-15% water. Women will be slightly less hydrated than men, due to the higher level of essential fat. Water is essential to life - it is present in all of your body fluids and tissues. In blood, it transports nutrients and oxygen to your cells, and picks up waste products for elimination. In sweat, it helps cool your body and in saliva and digestive fluids it helps break down the food you eat. Water is even a key ingredient for healthy, radiant skin!

While height and weight are valuable numbers to know, your body composition will tell you much more about your overall health, and it gives you some insight into what is going on inside you!

References:

Jordan, P., ed. (1995) Fitness: Theory & Practice. Aerobics and Fitness Association of America.

Clark, N. (1995) Water: the Ultimate Nutrient. Physician and Sports Medicine, 23:5: 32g-32h.