Well-toned muscles and a lean six-pack are often the aim, if not always the result, of working out. However, just because someone looks fit on the outside doesn't necessarily mean he is healthy on the inside, as fitness and health, things that can and should be closely associated, are often very different things.
What is Fitness?
Fitness is the successful adaptation to exercise. If you lift a heavy weight, your muscles get stronger so that the next time you lift that weight, your body is better able to deal with the stress. Likewise, if you run a mile, your body will make the necessary changes so that the next time you run, you're able to do it more easily. Fitness is specific to the type of exercises you do. Someone who runs for exercise will become a better runner but not a better weightlifter. A sprinter who always does high-intensity, short duration training will not be a good marathon runner. If you want to be all-around fit, you need to do a variety of types of exercise.
What is Health?
Health can be defined as the soundness or general well-being of an organism or the absence of disease. Health can be influenced by environmental factors such as pollution, a sedentary lifestyle or poor diet and genetic factors like a familial predisposition to certain medical conditions such as Type I diabetes or hyperlipidemia. While genetic predispositions are hard to avoid, there are several things you can do to maximize your health such as exercising regularly, eating a nutritious, balanced diet and minimizing stress levels.
Fit But Unhealthy
Being fit doesn't automatically mean you're healthy, although it is a step in the right direction. For example, a long-distance runner may be very cardiovascularly fit, but because of the high volume of training may have a suppressed immune system, be suffering early onset osteoarthritis because of the high running mileage and have poor posture because of the repetitive action of running. A football player will be fit for football, but because of repeated heavy tackles, a high body weight, possible use of performance-enhancing drugs and a lack of low-intensity aerobic exercise, could not be deemed to be healthy. The higher the level of sports or fitness performance, the higher the potential for poor health is likely to be because of the sacrifices necessary to reach such high levels.
Healthy But Unfit
As health can be described as the absence of disease, it is possible to be healthy but unfit. While exercise does provide a degree of protection from many medical conditions such as high blood pressure and coronary heart disease, health can be as much about genetic luck as it is about whether you do or don't exercise. Exercising and therefore being fit increases your chances of being healthy and living a long life but there are no guarantees that being fit means you won't suffer from poor health at some point.
Getting the Balance Right
Moderate amounts of exercise and following a healthy lifestyle means you can be both fit and healthy -- genetics notwithstanding. Extremes in exercise or poor lifestyle choices can significantly impair your health. The benefits of running, for example, could be all but be cancelled out by the health risks of smoking or drinking excessive alcohol. By avoiding obvious healthy pitfalls such as tobacco, recreational drugs and a nutritionally poor diet, you remove many of the things that can adversely affect your health. Regular, moderate, varied exercise will take care of your fitness.