In addition, Rand and MacGregor (1991) reported that individuals who had lost weight
following gastric bypass surgery stated that they would rather be deaf, dyslexic, diabetic,
have heart disease or acne than return to their former weight. These studies suggest a
relationship between body size and depression. However, it is possible that depressed
obese individuals are more likely to seek treatment for their obesity than those who are
not depressed and that there may be many obese individuals who are quite happy and
therefore do not come into contact with health professionals.
In contrast to the above studies, Halmi et al. (1980) reported that although just over
28 per cent of a group of 80 patients waiting to have a gastric bypass operation were (or
had been) clinically depressed, they argued that this is compatible with the prevalence
of depression in the general population. Therefore, although some obese people may be
depressed there is no consistent support for a simple relationship between body size and
psychological problems.WHAT CAUSES OBESITY?
The theories relating to the causes of obesity include both physiological theories and
behavioural theories.Physiological theories
Several physiological theories describe the possible causes of obesity.Genetic theories
Size appears to run in families and the probability that a child will be overweight is
related to the parents’ weight. For example, having one obese parent results in a 40 per
cent chance of producing an obese child and having two obese parents results in an
80 per cent chance. In contrast, the probability that thin parents will produce overweight
children is very small, about 7 per cent (Garn et al. 1981). However, parents and children
share both environment and genetic constitution, so this likeness could be due to either
factor. To address this problem research has examined twins and adoptees.Twin studies Twin studies have examined the weight of identical twins reared apart,
who have identical genes but different environments. Studies have also examined the
weights of non-identical twins reared together, who have different genes but similar
environments. The results show that the identical twins reared apart are more similar in
weight than non-identical twins reared together. For example, Stunkard et al. (1990)
examined the BMI in 93 pairs of identical twins reared apart and reported that genetic
factors accounted for 66–70 per cent in the variance in their body weight, suggesting a
strong genetic component in determining obesity. However, the role of genetics appears
to be greater in lighter twin pairs than in heavier pairs.356 HEALTH PSYCHOLOGY