The human body is a complex machine, working on its program. However, that she would not let failures, it needs a good "maintenance". In our case, this means a healthy, balanced diet and regular exercise. Hundreds of thousands of years ago, our ancestors spent his entire life in search of food. Forest fruits, seeds, nuts, roots and berries needed to find and collect, and meat extract hunting.
We had to travel long distances to find water, and all the time to be alert to repel an attack. The strength and agility were essential for survival and procreation, and if the person becomes ill, he was doomed.
Today in western countries, hunting is to hike to the supermarket, usually by car, and buying food and drink - often in larger quantities than is necessary. Many products are processed, during which all the "useless" is removed, and to give a pleasant taste add sugar, salt and fat. We hardly use our muscles to find and cooking machines perform for us all the hard work, and we simply do not need to be in shape to survive. Even if we get sick, doctors are able to cure most common diseases.