Obesity Treatment 195instance and should be stopped if a 10 percent reduction in weight has not
been achieved. Continued drug use beyond this time should be accompanied
by review and close monitoring (Kopelman, 1999b).
There are currently two groups of anti-obesity drugs available which are
offered in conjunction with dietary and exercise programs. Those in the first
group work on the central nervous system and suppress appetite. The most
commonly used of these are phentermine, which acts on the catecholamine
pathway, and sibutramine, which acts on the noradronergic and seroton-
ergic pathways (see chapter 3). There is some evidence for the effectiveness
of these drugs although they can also be accompanied by side effects such
as nausea, dry mouth, and constipation (Lean, 1997). The second group
of drugs currently in use acts on the gastrointestinal system, and the more
successful of these reduce fat absorption. Orlistat is one of these and has
been shown to cause substantial weight loss in obese subjects (James et al.,
1997; Sjostrom et al., 1998; Rossner et al., 2000). It can, however, be
accompanied by a range of unpleasant side effects, including liquid stools,
an urgent need to go to the toilet, and anal leakage, which are particularly
apparent following a high-fat meal. Rucker et al. (2007) carried out a meta-
analysis of 30 trials involving the medical management of obesity and con-
cluded that drugs can modestly reduce weight above that achieved by placebo.
In particular, orlistat reduced weight by 2.9 kg, sibutramine reduced weight
by 4.2 kg, and rimonabant reduced weight by 4.7 kg. Several drugs have
recently been withdrawn from the market. For example, both fenfluoramine
and dexfenfluoramine were withdrawn because of their association with
heart disease, and rimonabant has recently been withdrawn from the
market due to an increase in psychiatric (particularly mood) disorders.
Psychological impact of orlistat
Although orlistat is a medical approach to managing obesity, it also has
psychological implications. First, although orlistat is designed to work by
reducing fat absorption, it probably also has a deterrent effect, as eating
fat causes unpleasant consequences. This has been called the “antabuse effect,”
relating to the impact of the drug antabuse used for alcoholics which makes
them vomit if they consume alcohol (Finer, 2002). The drug provides imme-
diate costs to overeating. In 2006, Ogden and Sidhu carried out a qualitative
study to explore the psychological processes behind the success or failure
of orlistat. They interviewed patients who had taken the drug and concluded
that although it constitutes a medical approach to obesity, it provides a
window into the processes of adherence to medication and behavior change