Set Point Theory
Each person has
a weight range within a few pounds which is health and normal for that person. This range is called the set point. When someone
eats when they are hungry, stops when they are full and exercises in moderation, they will arrive at a weight that is healthy
and natural for them. When we try to go below our set point weight our bodies defense mechanisms against starvation kick
in. A person's metabolism is decreased, therefore, we burn fewer calories in an attempt to maintain optimal health. Studies
indicate that metabolism is decreased by as much as 40%.
Symptoms, such as, increased obsessional thinking about food,
weight and hunger, increased duration and intensity of hunger are the body's attempts to resist significant deviation from
the set point.
A theory suggesting that body
weight is kept relatively constant by internal control mechanisms similar to those of a thermostat. According to the theory,
each adult has a range of body weights that act as a norm or set point; changes in body weight trigger mechanisms to bring
the weight back to this set point.
Some researchers believe that the set point is psychological. An individual
establishes a perceived set point weight based on personal and cultural preferences. These preferences may be influenced
by the person's appearance, body weight measurements, clothing size, health, and so on. Deviations of weight result in changes
of physical activity and eating habits that return the weight back to the set point. Other researchers believe that the set
point is physiological, but there are a number of different mechanisms proposed. One proposal is that the set point depends
on the activity of the hypothalamus, a hormone-secreting gland at the base of the brain; another proposal is that a hormone
is secreted by adipose tissue. In either case, it is suggested that deviations of weight result in a physiological corrective
mechanism (e.g. change in basal metabolic rate) being switched on. Although dieting does not appear to affect the set point,
exercise may lower it, making it easier to lose weight.
A
theory that postulates that body weight is regulated around a given set point using a homeostatic mechanism similar to that
which regulates temperature. Preliminary studies indicate that people who lose weight through semi-starvation or gain weight
by overeating return to their normal body weight quickly when they revert to normal eating patterns. It has been suggested
that the body has the ability to balance caloric intake and expenditure to within plus or minus 10-15 kcal day−1.
It appears that the body attempts to maintain its normal weight when overfeeding or underfed by changing the three components
of expenditure (see resting metabolic rate, thermic effect of food, thermic effect of activity). If the set point theory is correct, it explains why some athletes have
great difficulty losing or gaining body weight for weight-classification sports, such as wrestling and horse riding.
