by Steve Edwards

A major health headline this week was a study dispelling the notion that you can be both fit and fat. Last fall, the wires were abuzz with citations about the dangers of being thin and fat (so-called "skinny fat"). With a national obesity rate of nearly 30 percent, we know that we're overweight. But if thin isn't the indicator of fitness, and you can't be large and fit, how are we supposed to tell if we're healthy? Let's decipher what these studies indicate and sort through the murkiness about what it really means to be fit.

Can you be fit and fat?

The latest issue of Archives of Internal Medicine reported a study of 39,000 women that suggested that fitness isn't the only indication of one's risk for developing heart disease. The subjects were between 50 and 60 years old and were tracked for 11 years. Nearly 1,000 got sick. The study showed that overweight women had a 54-percent greater risk of developing heart disease than those with similar exercise patterns who were not considered overweight. It also concluded that women who exercised, heavy or not, were two-and-a-half times less likely to get heart disease.

However, the study wasn't fastidious in its parameters. It relied on self-reporting and used the BMI (body mass index) scale, rather than actual fitness tests, to determine the subjects' fitness levels. This is where the study becomes questionable.

We tend to like things that come in simple-to-understand terms. Therefore, the government decided that we'd use the BMI scale to decide how healthy we are. It simply assigns you a number based on your height and your weight, leaving out such trivialities as lean muscle mass, body fat, basal metabolic rate, and other medical parameters. You may surmise that we all come in different shapes and sizes, so something as simple as BMI could be inaccurate. Your hunch would be correct.

While BMI can be a decent indicator across similar groups of people, it doesn't account for athletic body types. Using the BMI scale, almost every wrestler, bodybuilder, and NFL player would be classified as obese. And while heavier people, fit or not, induce more strain on their hearts, there are many other factors to consider prior to categorizing them as being vulnerable to health risks. Without knowing these other factors, it's difficult to make hard conclusions, especially when you consider that those with lower BMI numbers may be "skinny fat."

At least it was clear that those who exercised, whether heavy or not, greatly reduced their risk. The conclusions of the study seemed to miss out on something very interesting—a comparison between thin women who didn't exercise and heavy women who did.

Can you be skinny and fat?

Trying to answer the above question, we'll refer to a study from London's Imperial College showing that those who appear skinny to the naked eye but are unfit are still at risk to a rash of health problems.

Since 1994, Dr. Jimmy Bell and his team conducted MRIs on nearly 800 people, creating "fat maps" that show where they store fat. As it turns out, people who don't maintain their weight with a combination of exercise and diet keep huge fat deposits around their internal organs. The scientists theorized that excessive inner fat can confuse the body's communication systems, leading to heart disease, insulin resistance, or type 2 diabetes.

Again, fat and active people had a much lower mortality rate than the skinny and sedentary. This means that, as far as your health is concerned, a fitness test is a much better indicator than a scale or what size dress you fit into. As Bell explained to the Associated Press, "The whole concept of being fat needs to be redefined."

What does it mean to be fit?

Webster's tells us that fitness is "the capacity of an organism to survive and transmit its genotype to reproductive offspring as compared to competing organisms"; Dr. Fred Hatfield, in his book Fitness: The Complete Guide, gives us a more layman's view by defining it as: "Your ability to meet the exigencies of your lifestyle with ease and room to spare for life's little emergencies." Both definitions refer to functioning in the present as the main indicator, meaning that all these studies on heart disease in aging individuals probably aren't even the best bases to use to make conclusions about an individual's state of fitness.

Fitness is, in the simplest terms, your ability to perform in the world. We all have different goals and agendas and, in the end, we're all going to die. But there are a few things that we all share, no matter what kind of life we lead. If we consider the eight parameters below, and if we can perform them decently, we can consider ourselves to be fit. And, more than anything else, a fit life is probably a lot more fun than a non-fit one.

1. Body-fat percentage. This is the percentage of your total body weight that is composed of fat. Ten percent to 14 percent is considered good for men, and 14 percent to 18 percent is considered good for women. Unless you're a weight-dependent athlete or a fitness model, you don't need to go to extremes, but all of us should strive to be within this range. Being far under it has health risks too but going above it is what most of us need to worry about—and what the obesity epidemic sweeping the world is focused on. Not only does excess weight put our bodies under extra strain, but excessive amounts of fat change our abilities to function properly. So far more than your weight, you should be focusing on keeping your body-fat percentage within this range.
2. Aerobic endurance. This is how efficiently your body transports oxygen. It's a baseline fitness parameter that aids every more intensive fitness effort, from yard work to sex to running a marathon. Indicators of good aerobic fitness are a low resting heart rate and the ability to recover quickly after cardiovascular activity. You help increase this endurance by doing any type of activity but more efficiently when you do continuous low-level activity, like hiking or jogging.
3. Muscle mass. Like body fat, our bodies require a certain percentage of muscle to stay healthy. This varies per individual, but we all need muscle to meet the tasks of daily living. Above the age of 30, our bodies lose muscle mass each year, so it's important to do resistance exercise to keep muscle mass. Besides aiding movement, muscle mass protects our organs and skeletal structures. To age gracefully, it's vital to keep our muscle mass percentages high.
4. Flexibility. This isn't the ability to do pretzel-ish yoga movements but simply your ability to move your body freely through a full range of motion. It's important that we stretch our muscles because they contract during exercise and the daily rigors of living. Keeping your muscles supple gives you a buffer against being injured and is an indicator of overall fitness. It will help you age without as many complications.
5. Strength. Strength is the ability to use your muscles to generate force. It's often defined in more specific terms, like limit, starting, or explosive strength, but they're all a variation on the same theme—your body needs to be able to move stuff around. Most importantly, it needs to move you around. As we age, we lose muscle mass and strength. Mass protects your body. Strength moves it and keeps it from falling over. Furthermore, strength training requires short bouts of high-intensity outputs. These stimulate hormonal responses that also decline as we age. In a nutshell, strength training slows the aging process. The stronger you are, the slower you age.
6. Static balance. This is your ability to maintain control of your body's center of gravity over your base of support. The importance of this ability is obvious, since life's no fun if you're always toppling over. It requires use of all of the aforementioned factors, and the best way to get it is to practice. What's really important is that to stay in balance your body uses smaller muscles, called stabilizer muscles (the large ones you see are called prime mover muscles); and these help keep your joints tracking properly. A person with good balance has less chance of incurring an injury, especially an injury due to overuse.
7. Dynamic balance. This is the same as the above, except you control your center of gravity while in motion or in flight. The eccentric motions created in practicing dynamic balance not only stimulate hormonal responses but fire something called high-threshold muscle cell motor units. It's important to train dynamic balance as you age and, symbiotically, training this action helps keep you young.
8. Agility. This is your ability to move dynamically in different directions quickly and randomly. It requires that you use starting strength, explosive strength, limit strength, and dynamic balance in combination, so all of those areas must be conditioned. Plyometric training, like that incorporated into Tony Horton's P90X®, in combination with stretching, helps you stay agile as you age.

Steve Edwards is the fitness and nutrition advisor at Beachbody Fitness Solutions. This means that if any of our products don't work it's my fault so go ahead and challenge me. I also write, make movies, play a lot of outdoor sports and regularly mimick a lab rat to test my own theories on nutrition and exercise