Coping with the Obesity Pandemic

Is there an obesity pandemic in most countries these days?

Posted Apr 22, 2013

Is there an obesity pandemic in most countries these days?  According to Bruce M. King in an article published recently in American Psychologist, the answer is a definite yes.  A professor of psychology at Clemson University in Clemson, South Carolina, Dr. King has published over sixty papers on the neurobiology of feeding behavior and body weight regulation and is also a noted authority on human sexuality.  

According to most available health statistics, obesity constitutes one of the main health problems facing most societies today.   Using the most commonly accept definition of obesity as having a body mass index (BMI) of 30 kg/m2, over 502 million people are obese while another billion are overweight (having a BMI greater than 25 kg/m2).    In the United States alone,  35.7% adults are obese while an additional 33.1% are overweight according to a 2010 survey with over 6% of Americans meeting the criteria for extreme obesity (BMI greater than 40 kg/m2).   

One of the most unnerving aspects of the modern obesity epidemic is that it is a relatively new phenomenon.  Older studies by the U.S. Public Health Service show that only 1 in 5 adults were overweight back in 1960 and this remained relatively stable until the 1990s when the percentage of obese Americans began steadily increasing.   According to one disturbing modelling study examining current and future trends,  as much as 51% of the U.S. population will be obese by 2030.   That same study suggests that even keeping obesity at 2010 levels could save $549 billion in health care costs. 

The problem is even worse among American children with obesity rates tripling since 1980 and similar trends being noted in many other countries.  Despite public health campaigns to curb obesity and increase physical activity, the problem of reducing obesity is still unsolved. 

Even modest weight loss can be a heartbreaking task for most people who often gain the lost weight back fairly quickly.   Whether through diet, exercise, or a combination of both, permanent weight loss can be elusive.   It’s hardly surprising that the sale of weight loss products and clinics is a multi-billion dollar industry with an estimated $30 billion being spent annually in the United States alone.  Still, despite being bombarded with ads for painless, simple weight loss methods, there really are no easy answers out there.

So why is obesity so difficulty to overcome?  While researchers have identified brain pathways and neurotransmitters that appear to be linked to overeating and obesity, the question of why overeating happens and what has led to the recent obesity epidemic is not that easy to answer.  Pharmacological and surgical treatments designed to reinforce the body’s own homeostatic mechanism curbing overeating, including leptin therapy and stomach stapling in extreme cases often result in only small to modest permanent weight loss.   Physiological researchers have found that environmental influences account for over 86% of variance in daily food intake in free-living humans living in a regular environment, i.e. you and me.   Even moving to another part of the world where we are encounter unfamiliar foods can often be enough to make us put on a lot of weight (something to bear in mind when on vacation).    

According to Dr. King’s review article, humans are genetically predisposed to consume high-fat and high-calorie foods and to gain excess body weight.  Understanding why that is means recognizing that we are the product of our own evolutionary history.  Our hunter-gatherer ancestors often traveled long distances to scrounge the necessary amounts of meat and vegetation to stay well-fed.  Survival meant consuming as much animal fat and carbohydrates as possible whenever these foods became available.  

Overeating was rarely a problem for hunter-gatherers but that all changed with the “agricultural revolution” 10,000 years ago in most places.  Though agriculture was a back-breaking challenge for most of human history,  that has changed enormously in the past century to the point where most of us can now enjoy a high fat and carbohydrate diet that is far greater than the amount of work we need to produce it. 

Since evolution works slowly, we are reacting to this modern abundance of food in the same way that our hunter-gatherer ancestors would and often lack the self-restraint that would keep us healthy (King refers to this as an “obesogenic environment”).   Though not all of us are obese, moderate eating habits are often difficult to stick to given the variety of food choices currently available.    Not only is body weight often genetically determined (twin studies show that as much as 55 to 85 percent of variance in BMI linked to genetic factors), but we are also bombarded by tastes and smells that motivate us to eat in the same way our hunter-gatherer ancestors would. 

The taste receptors in the tongue and the olfactory receptors in the nose are both directly linked to parts of the brain mediating pleasure, among other things.  Sweetness in food is a particular culprit since taste receptors for sweetness are at the very tip of the tongue.  While our ancestors often rarely experienced sweetness (except in fruit, which was often unavailable for much of the year), controlling our “sweet tooth” can be especially difficult.  It is even harder to curb that same sweetness craving in children who fail to recognize the potential health risks involved.   

One particular culprit, refined sugar was once a luxury item which only became readily available worldwide by the 19th century.   Today, sugar is deemed an essential item with Food and Agriculture Organization statistics showing an average annual consumption of 24 kilograms (53 lbs) of sugar per person for all ages worldwide in 1999 alone. 

And sugar is just one of the various ingredients added to food these days to make them tastier.  A diverse choice of tasty foods (such as in a multi-course dinner) can often tempt people to overeat due to the range of different taste sensations involved.  Even laboratory animals have been shown to overeat when presented with multiple food choices (known as a “cafeteria diet”).   While taste and smell alone are not enough by themselves to make us overeat, they can be an important contributing influence, especially in the “fast food” world in which we find ourselves.

Research comparing obese and lean people has turned up some important differences in brain structure and chemistry including how food taste, smell and texture triggers the brain’s “reward” systems.   Obese people seem especially vulnerable to seeking out immediate food rewards rather than being able to delay gratification the way lean people can.   Also, obese people are also more vulnerable to external cues while lean people rely on their own internal system to tell them that they have eaten enough.   In many ways, these differences are similar to brain research on drug and alcohol addicts who often share many of the same characteristics as obese people in responding to external cues.   Obesity is also linked to specific genetic markers involved in dopamine reward systems and neuroimaging studies in children at risk for obesity due to these same markers have also found hyperactivity in the brain reward circuitry.

So what does all this mean for dealing with the obesity epidemic?   As Dr. King suggests, we are poorly equipped to cope with the obesogenic society we’ve created for ourselves.   We are besieged by ad campaigns designed to introduce us to a greater range of food choices than our ancestors ever dreamed about.    The biological drive to experience pleasant taste sensations can lead to unwise food choices, especially in formerly obese people who have managed to lose weight and are struggling with the temptation not to reward themselves.  

While it is easy to advise people that they need to change their eating habits, simply walking through a food court at the nearest mall means being overwhelmed by vivid smells that cue the brain to respond.   Coming to terms with these temptations, especially in a society that encourages us to overeat is a challenge we all need to face.