Given that eating behavior is influenced by both biological and social factors, determining the causes of obesity has proven to be a challenging task. Researchers have followed several paths.

Some psychologists suggest that an oversensitivity to external eating cues based on social convention, and a parallel insensitivity to internal hunger cues, produce obesity. Research has shown, for example, that obese people who are placed in a room next to an inviting bowl of crackers are apt to eat considerably more than nonobese people - even though they have just finished a filling sandwich. In addition, obese individuals are less apt to eat if doing so involves any sort of work.

In one experiment obese participants were less likely to eat nuts that had to be unshelled, but ate copious amounts of nuts that already had their shells removed. Nonobese people, in contrast, ate the same amount of nuts, regardless of whether or not they had to be shelled. Consequently, it appears that many obese people give undue attention to external cues, and are less aware of the internal cues that help nonobese people regulate their eating behavior.

On the other hand, many individuals who are highly reliant on external cues never become obese, and there are quite a few obese people who are relatively unresponsive to external cues. Consequently, some psychologists have turned to weight set point theory - the particular level of weight that the body strives to maintain, as a plausible explanation for the cause of obesity.

Specifically, these researchers suggest that overweight people have higher set points than people of normal weight. Because their set points are unusually high, their attempts to lose weight by eating less may make them especially sensitive to external, food-related cues and therefore more apt to eat, perpetuating their obesity.

But why may some people's weight set points be higher than others? One factor may be the size and number of fat cells in the body, which increase as a function of weight increase. Because the set-point level appears to reflect the number of fat cells a person has, any increase in weight - which produces a rise in fat cells - may raise the set point.

Furthermore, any lose of weight after the age of two does not decrease the number of fat cells in the body, although it may cause them to shrink in size. In short, according to the weight set point hypothesis, the presence of too many fat cells may result in the set point becoming "stuck" at a higher level than is desirable. Under such circumstances, losing weight becomes a difficult proposition, because one is constantly at odds with one's own internal set point when dieting.

Not everyone agrees with the set point explanation for obesity. Pointing to the rapid rise in obesity that has occurred over the last several decades in the United States, some researchers suggest that there is no fixed set point determining weight that the body attempts to maintain. Instead, they suggest, there is a settling point, determined by a combination of our genetic heritage and the nature of the environment in which we live.

If high-fat foods are prevalent in our environment, and we are genetically predisposed to obesity, then we settle into an equilibrium that maintains relatively high weight. On the other hand, if our environment is nutritionally healthy, genetic predispositions to obesity will not be triggered, and we will settle into an equilibrium in which our weight is lower.

Both the set point and settling point explanations for obesity suggests that genetic factors predispose us to obesity - a notion that is receiving increasing support. However, researchers are finding increasing evidence that particular genes control hormones in the body that are linked to weight.

Source from: Understanding Psychology, Feldman 2000

© 2003 by AfroStaff