Is being overweight and obese due to genetic reasons?
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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 increased activity of the enzymes and other factors involved in storing fat.
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.
Has modern society contributed to obesity?
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Regardless of the exact causes for obesity, one thing is certain: the incidence of obesity in many countries has increased dramatically within the past few decades. In fact, in many countries almost everywhere one turns a soda and/or vending machine can be found. It also seems that most of the commercials on television are for chips, soda, candy, and other energy-dense foods. Furthermore, many modern societies take great pride in developing ways to reduce people’s physical activity level. Escalators grace every mall; airports have moving sidewalks; and everywhere you go, you can sit down. All too often roads are constructed without sidewalks or bicycle lanes. |
Long ago, even eating itself involved significant energy expenditure. As hunters and gatherers, our ancestors had to spear their fish, hunt and scavenge animals, dig up roots, climb trees for leaves, and pick fruits and vegetables. Today, one simple trip to the convenience store or dialing a phone number yields a bounty of food. Even the act of preparing food, which could take hours even a generation ago has been greatly simplified and requires less expenditure of energy.
Are there different kinds of obesity?
Visually it may indeed seem as if there are different types of obesity. Some people, particularly men, seem to store more fat above the waist in the abdominal region, which is referred to as upper-body obesity. Often this body shaping is described as “applelike.” Others, especially women, store more fat below the waist in the buttocks and thighs which is referred to as lower-body obesity. This type of body design has been described as “pear shaped.”
People exhibiting the upper-body obesity pattern seem to be at a higher risk for heart disease, stroke, diabetes mellitus, and some types of cancers. In this type of obesity more of the fat is found deeper, surrounding internal organs in the abdomen. This fat tissue is referred to as visceral fat and researchers believe that this fat functions a little differently than fat found under the skin. While the reasons for preferential storage of fat in specific sites are still unclear, hormone levels (e.g., estrogen) and different levels of activity of fat-storing enzymes in different parts of our body probably play the biggest roles. These enzymes are called lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL).
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