Severely or morbidly obese persons are, on
the average, about 10 to 12 BMI units heavier
than their parents and siblings. Several studies
have reported that a single major gene for high
body mass was transmitted from the parents to
their children. The trend implies that a major
recessive gene, accounting for about 20 to 25
percent of the variance, is influenced by age and
has a frequency of about 0.2 to 0.3 (Bouchard et
al., 1998). However, no gene(s) has (have) yet
been identified. Evidence from several studies has
shown that some persons are more susceptible
to either weight gain or weight loss than others
(Bouchard and Tremblay, 1990). It is important
for the practitioner to recognize that the phenomenon of weight gain cannot always be attributed
to lack of adherence to prescribed treatment
regimens