During the
history of human evolution the process of accumulation of body fat was being
selected because it was beneficial in an environment where food was scarce and
the periods in which an individual could pass without finding an appropriate
source of nutrition were frequent and long (Speakman , 2007; Prentice et al.,
2008, Carvalho, 2009).
More
recently, from the evolutionary point of view, two major changes that the
introduction of agriculture brought were regular exposure to famine and
development of social hierarchies that result in a differential exposure to
environmental stresses (Wells, 2006). There are certain normal stereotypes that
were created as "fat is beauty" or "eat like an abbot," for
the accumulation of fat was a sign of health, status and wealth.
With the
rise of industrialization occurred transport improvements, significant
reduction of physical effort labor and access to high-calorie and mass
production food, which was creating an increasingly obesogenic environment (Bellisari,
2008). With this improvements of living conditions and access to nutritional
sources, especially in the last 30 years of the twentieth century in developed
countries and more recently in developing countries, this feature is no longer
beneficial and was becoming a problem (Bellisari , 2008; Carvalho, 2009).
In 1998 the
World Health Organization has recognized obesity as a chronic disease,
affecting both developed and developing countries, and adults and children
alike. It is a major public health problem and is overcome problems such as
malnutrition and infectious diseases (WHO, 1998).
Encarnação, 2011: Breakfast skipping and Obesity in Portuguese school children: Association with behavioral and family characteristics - unpublished Master thesis in Human Evolution and Biology, Coimbra University
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A clear explanation of the main evolutionary view of why we are vulnerable to obesity. It still seems that obesity (and type 2 diabetes, etc) has exploded across societies across the world - I cannot think of a case where a change in natural selection has acted so suddenly, except for responses to new pathogens.
ReplyDeleteAs evolutionary thinkers I suppose we should be concentrating on changes in the physical and social environment that might plausibly influence fat retention, and that seem to have changed at a time around when this pandemic began?
Also, if we had evolved to store as much energy as fat as possible, then - if this was stable - that suggests that the costs at that time were balanced by any benefits. I wonder what those costs were?
Of course the socioeconomic revolution has lead to likely risks from the calorie-dense foods we can now produce in factories; the temptation for manufacturers to increase sales by using high levels of sugars, fats & salt as well as cheap, unhealthy ingredients such as high fructose syrup; the political power of these companies that allows them to block change; the systems allowing these foods to be cheaply & efficiently transported to the whole world; and many such factors.
It is good to read research that critically examines the problem and possible key factors.