Now here's a little paradox for you to play with. As an insurance company, you prefer to insure people who are fit and healthy. That way you can collect in all the premiums and only rarely have to pay out. But if people play sport or run long distances, they are more likely to injure themselves. This means paying out more for their treatment. How do you square the circle? Well, let's look at the market. The majority of people who play sport are young and have the level of disposable income that allows them to pay for their own insurance. In marketing speak, they are a great demographic. To give you an idea of the size of the market, Boston recently went online for people to sign up for the 2011 Marathon. All the places were taken within eight hours. Yes, there really are that many people who believe they can travel 26 miles without the use of a motor vehicle. The only problem is that, if you take your sport seriously and train hard so your performance will be good enough, a significant proportion of people injure themselves or are involved in accidents. There are detailed statistics for distance running which proves that almost 80% of all runners are likely to suffer foot injuries. Put another way, couch potatoes rarely injure themselves, even when they fall off the couch after too much beer. Except, of course, couch dwellers will also have a high BMI, high cholesterol levels and will be aging faster through lack of exercise.

As the law currently stands, a young man who plays football could be refused coverage if he asks for a policy having just broken his arm in a game. It's a standard response from insurers to reject people who have a pre-existing condition. But when the health reforms come into force in 2011, insurers will have to accept the broken arm along with all the other pre-existing conditions. This probably means the same premium regardless whether you move from the couch or use parkour to get to work, jumping over fences and flipping off walls. This might seem unfair.

Those who invest in their own health by keeping fit say they should be rewarded by lower premiums. The method of setting the rate should be based on something more than age and gender. And some health insurance companies have begun to promote the idea of healthy lifestyles by offering lower premiums to those who show a good level of fitness in the medical exam, and can prove regular participation in an activity. This leaves us with one irony. Health insurance companies report that many active sports persons think they are invincible and have no need for a health plan. Unfortunately, participation in sport is not always proof of high intelligence. It's dumb and dumberer instead of healthy and healthier. This is not to say insurance companies are becoming less dumb. Many are still refusing coverage to healthy athletes based on the short-term risk of accidents and injuries. But, if we are to do something positive to rescue the US from obesity, we all need to become more active. The health of the nation depends on it.