This is a difficult question to answer in the manner in which we would like it to be answered. Quite simply, obesity results from an energy (calorie) imbalance whereby more energy is brought into our body than is expended. We store the bulk of excessive energy as body fat and the weight gain also includes supporting materials such as connective tissue, muscle, bone, etc. Certainly that seems simple enough. However, identifying the underlying reasons for the imbalance is a bit more complicated. Is it merely a matter of excessive energy intake, meager energy expenditure, or a combination of both? And, are we genetically programmed to promote the energy imbalance and body fat accumulation?
An argument can easily be made that nearly all aspects of our being have a genetic basis. Thus genetic disposition must be involved in determining body weight and composition. But how? Although "faulty genes" can certainly play a role in establishing a sluggish metabolism in some people, scientists estimate that this may account for only a small percentage of obese individuals. Here the problem may lie in hormonal imbalances, such as lowered thyroid hormone. Scientists also believe that some people are genetically inclined to store body fat and hold on to it once it is stored. In this situation the cause is not hormonal as much as altered activity of the enzymes and other factors involved in storing fat.
Obesity is caused by excessive calorie intake over time. Genetics can make certain people more susceptible to obesity in a variety of ways.
Can genetics pattern an individual's behavior, thereby rendering him or her more inclined to develop obesity? For example, people who prefer to be less active or favor energy-dense foods are likely candidates for an energy imbalance. If we apply genetics to the incidence of obesity in this manner, we can certainly attribute obesity in many people to a genetic origin of some form. For others, excessive energy consumption may be a manifestation of psychological disturbances. Here, food may serve more as an instrument of comfort or as a way to cope. The role of genetics in promoting obesity will continue to show that there are hundreds of genes that can play a role in the development of obesity; the hard part will be to apply this knowledge to help specific individuals.
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Studies show obesity may soon overtake tobacco as the leading cause of death in America. Are you ready to drop those extra pounds you've been carrying around? Awesome. Let's start off with a couple positive don't. You don't need to jump on a diet craze and you don't need to start exercising for hours each day.