Eating too much can cause obesity – that is obvious. In addition, there are environmental factors that may contribute towards a person becoming obese. Given the typical American lifestyle, it is no wonder that so many people in our society suffer from this problem. The consumption of fast food, sedentary lifestyles, and the common usage of cars rather than walking or bike riding all contribute to obesity. Sometimes a serious change of environment is needed in order to combat the problem obesity.
Then there is the issue of metabolism. Back in the old days, we used to believe that weight gain and loss was equal to the number of calories ingested and burned, respectively. We now know that the case is not so simple. Researchers have recently come up with a theory that they call "the set point theory." In laymen's terms, the idea is that there is a "set point" in the brain that can make people resist either the gain or loss of weight. If you exceed your brain's set point by drastically cutting the number of calories you consume, your brain's response may be to slow down your body's activities and lower your metabolism. As a result of this process, any weight you might have lost is ever gained back.
There has also been an increase in the average serving portions of food since the late 1970s. That increase has been especially prevalent in soft drinks and salty snack food. Other studies have established that people of today no longer stick to the recommended servings featured in the food pyramid of the USDA. By having an unbalanced diet, people have a higher chance of becoming morbidly obese.