If you ask most people what causes obesity they will tell you that obesity in quite simply the result of eating too much food and not taking enough exercise. But is it really as simple as that?

In one sense the answer to this question is yes and there can be little doubt that much of the obesity we see today is the result of nothing more than a combination of the modern diet and lifestyle. Fast food, convenience foods, take-away and spending our free time in front of the television or playing computer games accounts for not only much of the rise in obesity amongst adults, but also the dramatic rise in juvenile obesity.

Eating is essentially a balancing act. Our body needs a certain amount of energy each day to function and it gets that energy from the food we eat. Just how much energy the body needs will vary from one person to the next and will depend on various factors including the individual's level of activity. For example, a taxi driver who spends his day sitting behind the wheel of his cab will need less energy than a lumberjack who spends his day felling trees by hand.

If the amount of energy we put into our bodies exceeds the energy which the body requires then this 'additional' energy is simply stored as fat for use a later date if needed. This fact is generally well understood, but what is not so well understood is just how quickly fat can accumulate in the body.

Take for example two individuals both about 40 years of age. One is slightly overweight, carrying about 15 pounds of excess fat, while the other is obese and carrying about 100 pounds on additional fat. In both cases weight gain has been gradual and their weight has risen slowly over many years. Just how much overeating could produce these results? The answer will probably surprise you.

Our slightly overweigh individual would typically put on this sort of weight with as little as 4 unwanted calories a day or the equivalent of eating an extra apple about once every two and a half weeks. His obese companion on the other hand could have reached his present state of obesity with as little as an extra 25 calories a day, or the equivalent of an extra apple every three days. It make you realize all too quickly why today's diet of hamburgers, crisps and soda results in weight gain.

Of course this is only part of the picture and it would be wrong to say that obesity is solely the result of overeating and taking too little exercise. However, it would be equally wrong to produce a long list of alternative causes and to suggest that these are equally to blame. It is certainly true that there are other factors at play when it comes to obesity, but it is fair to say that bad eating habits and a lack of exercise are undoubtedly the primary cause of obesity today.