162 Obesity
A neural model of obesityThe role of neurotransmitters in understanding food intake was outlined
in chapter 3. In terms of obesity, it could be argued that people overeat
and gain weight because they have too many neurochemicals that promote
food intake and too few that cause satiation. Recent developments in this
area suggest that body fat may be an active organ rather than a benign struc-
ture and may promote hunger and subsequent eating behavior. It may, there-
fore, be the case that even if the stage of becoming obese (the dynamic stage)
is not directly linked to overactive neurochemicals, once the individual has
gained surplus body fat (the static stage), they then feel more hunger and
are less sensitive to the normal signals of satiation.
An evolutionary model of obesityAccording to an evolutionary approach to behavior, current human behavior
can be understood in terms of how it may have been adaptive in our ances-
tral past. Evolutionary psychologists refer to this as the ultimate explanation.
So although current behaviors may appear to be maladaptive or dysfunc-
tional, evolutionary psychologists argue that they can be analyzed and under-
stood as having been adaptive and functional in some way in the past. To
undertake this type of analysis, they draw on the theory of natural selection
and suggest that all species, including humans, evolve through a process
of natural selection and that only those characteristics that confer advan-
tage, or at least do not confer disadvantage, survive as the species evolves.
This is an interactionist approach, as an individual’s genetic predisposition
is assumed to interact with their environment.
An evolutionary model of obesity is interested in whether the tendency
to be overweight and store excess body fat could have been adaptive in our
ancestral past. Since much of our past has been characterized by a relative
lack of food, compared with conditions in the Western world today, it would
be reasonable to assume that the tendency to store fat would have been
functional in a world where food was often in short supply.
Some researchers have argued for the “thrifty gene” hypothesis of obesity
to support this approach. This hypothesis, first proposed by James Neel,
argues that over thousands of years those individuals who were most energy
efficient in terms of burning off excess energy and remaining thin would
have been less successful, although this is now highly prized in the twenty-
first century (Neel, 1962). Evolutionary mechanisms would therefore have
selected against such people in favor of those who stored excess body fat