Obesity: an evolutionary by product?

As part of national obesity week  2020health is running a series of blogs building on the success of our recent report Careless eating costs lives.

The blogs will cover various themes which speak to the obesity challenge the UK currently faces. This will include looking at how human biology, our new lifestyles and the modern food supply has helped to contribute to the rise in obesity; the various factors which shape how we eat; what effective behavioural change may involve and the economic impact of poor health and diet.

Obesity is a problem of modern society with statistics only emerging within the last 50 years. In its relatively short existence, obesity has become an international pandemic. In 2002, the international obesity task force estimated that 6 percent of the world’s population was overweight or obese (Coviello & Nystom, 2003). By 2008 these statistics had risen to 30 percent of the global adult population classified overweight and 11 percent clinically obese.

These figures have continued to rise so much so that in today’s society, the majority of the world’s population live in countries where more deaths are associated with overweight than underweight (Basu et al, 2013). WHO currently predicts that by 2015 2.3 billion adults will be overweight with an excess of 700 million of those obese worldwide².

In the UK, the obesity epidemic is a major population and public health issue. It is a complex problem requiring action at a national, local, family and individual level. In 1985, the ‘Health of the Nation’ report proposed a target to return obesity levels to those observed in 1980 (6 percent for men and 8 percent for women). This target was missed by 400 percent. Without effective interventions, it is predicted that 60 percent of adults in the UK will be obese by 2050 (Basu et al, 2013),

There appears to be no single cause for the observed rise in the incidence of overweight and obesity. The complexity of the situation arises from the interplay of a plethora of evolutionary, historical, scientific, environmental, social and individual factors. The vast ranges of causal influences lie at the heart of the conundrum when considering the best approach to counteract the ‘obesity epidemic’.

During National Obesity Awareness Week 2015, we will look to explore these factors in later blog posts this week. But for now let’s ask the question: how do we come to be in this position in the first place?

Humans as victims of their own evolutionary success

As is so often the case with finding solutions to problems, to begin to grasp what needs to happen in the future, we need to first turn and reflect on what has gone before. In responding to obesity, we need to look at how our diet has evolved. The western diet differs from the conditions under which human metabolic physiology evolved (Pontzer et al, 2012).

The environmental pressures of our ancestors ensured that the acquisition of a high quality diet required vigorous physical activity; this was often followed by episodes of food deprivation and negative energy balance. The human race, like all species has evolved through the process of natural selection. In the early stages of human evolution, our expanding brains, shrinking large intestines, lengthening small intestines and the emergence of Homo erectus had profound implications on our nutritional needs (Armelagos, 2010). The evolving body required energy dense foods. Foods, particularly fatty and sugary foods have obtained intrinsic reward value through this process of evolution (Weltens et al. 2014). High fat food foraging was naturally selected, fat provided energy stores for hunter-gatherers in times of moderate-negative energy balance.

A hallmark of human evolution is our ability to find food in almost any environment and improve the efficiency with which we extract it (Leonard, 2014). Human husbandry, agriculture, urbanisation and globalisation have occurred within the last 10,000 years, human evolution cannot keep up with our rapidly changing environment. We observe major clashes between human biology and modern society (Popkin et al, 2011). The evolutionary collision of our ancient genome with the nutritional qualities of recently introduced foods and a society in which technology caters to our every need, could underpin the obesity epidemic and the lifestyle diseases of our society (Cordain et al, 2005).

The Omnivore’s dilemma

Human nature and the success with which our ancestors solved what is known as the ‘omnivore’s dilemma’ are integral components in the evolution of the western diet and eating patterns in the modern setting (Armelagos et al, 2014).

Three human attributes that comprise the ‘omnivore’s dilemma’ are:

• Food neophobia (fear of new foods)
• Food neophilia (desire to try new foods)
• Sensor specific satiety (palate fatigue, boredom from over consumption of the same food).

As humans we are biologically programmed to eat a variety of different foods to ensure that we meet our nutritional needs. Food neophobia prevents this, but helps to ensure that we consume safe foods. Food neophillia and sensory specific satiety facilitate a varied diet (Remick et al, 2009 & Armelagos et al, 2010).

Cuisine, agriculture and animal husbandry arose as a solution to the omnivore dilemma (Armelagos, 2010 & Cordain et al, 2005). They are essential features of human dietary adaptation and the evolution on the western diet.

Today we see a global food system producing more processed, affordable, effectively marketed and varied food than ever (Swinburn et al, 2011). It is therefore understandable how human biology, our new lifestyles and the modern food supply has helped to contribute to the rise in obesity. Understanding where we have come from helps us to respond to the current ‘obesity epidemic’ we face and addressing the complex interplay of evolutionary, historical, scientific, environmental, social and individual factors which arise. How we set about doing this will be the focus of our next blog post.

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References:

Armelagos, GJ. 2009. Brain evolution, the determinants of food choice and the omnivore’s dilemma. Critical reviews in food choice and nutrition. 54: 1330-41

Armelagos, GJ. 2010. The omnivores dilemma. The evolution of the brain and the determinants of food choice. Journal of anthropological research. 66(2): 161-86

Armelagos, GJ. 2014. Brain evolution, the determinates of food choice, and the omnivore’s dilemma. Crit Rev Food Sci Nutr. 2014;54(10):1330-41. doi: 10.1080/10408398.2011.635817.

Basu, S., McKee, M., Galea, G., Stuckler, D. 2013. Relationship of soft drink consumption to global overweight, obesity, and diabetes: a cross-national analysis of 75 countries. Am J Public Health. 2013 Nov;103(11):2071-7. doi: 10.2105/AJPH.2012.300974. Epub 2013 Mar 14.

Cordain L, Boyd-Eaton S, Sebastian A, Mann N, Lindeberg S, Watkins BA, O’keefe JH, Brand-Miller J. 2005. Origins and evolution of the western diet: health implications of the 21^st century. Am J Nutr. 81: 341-54

Coviello JS, Nystrom KV. 2003. Obesity and heart failure. J cardiovas nurs. 18(5): 360-6

Leonard WR. 2014. The Global diversity of eating patterns: Human nutritional health in comparative perspective. Physol Behav

Pontzer H, Raichlen DA, Wood BM, Mabulla AZP, Racette SB, Marlowe FW. 2012. Hunter gatherer energetics and human ovesity. Plos one

Pokin BM, Adair LS, Ng SW. 2011. Global nutrition transition and the pandemic of obesity in developing countries. Nutrition reviews. 70(1): 3-21

Popkin BM. 2006. Global nutrition dynamics: The world is shifting rapidly towards a diet linked with non-communicable disease. Am J Clin Nutr. 84: 289-98

Remick AK, Polivy J & Pilner P. 2009. Internal and external moderators of the effect of variety on food intake. Psychol. Bull, 135(3) 434-51

Swinburn B, Sacks G, Ravussin E. 2009. Increased food energy supply is more than sufficient to explain the US obesity epidemic. Am J Clin Nutr. 90: 1453-6

Swinburn BA, Sack G, Hall KD, Finegood DT, Moodie ML, Gartmaker SL. 2011. The global obesity pandemic shaped by global drivers and local environments. Lancet. 378: 804-14

Weltens, N., Zhao, D. and Van Oudenhove, L. (2014), Where is the comfort in comfort foods? Mechanisms linking fat signaling, reward, and emotion. Neurogastroenterology & Motility, 26: 303–315. doi: 10.1111/nmo.12309