As incredulous as it may sound, we live in a world where obesity is a bigger health crisis than hunger and smoking. Most of the world’s population lives in countries where obesity kills more people than malnutrition.  

From Vellore to Virginia (with the exception of sub-Saharan Africa), mankind has fallen prey to ever-expanding waistlines, thanks to improving standards of living and easy availability of food. 

According to the Global Burden of Disease study released in 2016, close to a third of the world’s population—2.2 billion people—are classified as obese or overweight. Given that not a single country has managed to reverse this trend in over three decades, McKinsey forecasts that over half the world’s adult population will be overweight by 2030. 

Apart from the obvious personal and psychological costs, obesity’s economic burden surpasses $2.8 trillion a year, equivalent to economic cost imposed by smoking, or war, terrorism, and armed violence.  

Not surprisingly, weight loss (and maintenance) are highly coveted goals, perennially at the top of personal wish lists and New Year's resolutions. But when the best-laid plans go haywire a few days into the year, people find their favourite culprits to bash—a sedentary lifestyle, lack of exercise, failure to control oneself in the face of temptation, or even genes.  

The internet abounds with wisdom on how to lose weight—with most people sticking to either of the two camps (unless they blame their genes for all the excess pounds and problems). Most people believe that excess weight is caused either due to lack of exercise or excessive food intake. Once they join one of these two camps, they can find plenty of evidence to confirm their hunch.  

Not surprisingly, we have all heard (or said) things like “it doesn’t matter how much you eat, as long as you burn it off" or on the other side “leave the table while you feel you could eat a little more".  

To those who condone the former, I say, do you know how many minutes of exercise or miles of walking are needed to burn off a lone (mini) cupcake? (A little under 2 kms of brisk walking, for those interested) No wonder Google’s attempt to measure walking distance in sweet treat calorie equivalents was a non-starter

Resist or respond?  

So which camp do you belong to? What, do you think, is the cause of weighty woes? Is it worthwhile to muster up every ounce of will power in your body and walk away from that muffin or is it fine to devour one (or a few, if you are like me) and then try to sweat it off later? 

Extant scientific evidence shows that the primary cause of obesity is caloric over-consumption. Simply put, eating more is the biggest driver of excess weight. That exercise can help you lose weight is a myth.  

This is not to say that exercise isn’t good for you. While it is indeed theoretically possible to “burn" of those excess calories with more exercise, people are over optimistic about how much they think they can burn off (remember the Google Cupcake fiasco above?) and routinely under estimate how much they overate.  

What is even more fascinating, is that these naïve theories—whether obesity is caused by (excess) food eaten or by (lack of) exercise—have a pervasive influence on how healthy you are. 

In their 2013 paper published in Psychological Science, Brent McFerran and Anirban Mukhopadhyay asked people what they believed to be the primary cause of obesity. Only half the participants (correctly) believed that excess eating was the primary cause of obesity. More surprisingly, this had a bearing on their actual Body Mass Index (BMI, an index derived from weight and height of an individual and is used as a screening tool to indicate whether a person is overweight, underweight, obese, or healthy for their height). 

They found that those who indicted lack of exercise or genetics as the culprits had significantly higher BMI than those who believed that excess food intake is the primary cause of obesity. BMI is the most practically relevant/useful, widely used, and WHO-recognized indicator of obesity. It’s easy to measure/calculate (non-invasive) and it correlates well to direct measures of body fat such as underwater weighing and dual-energy X-ray absorptiometry (DXA). It is a “screening tool" to identify potential weight problems (to classify people as underweight, healthy, overweight, or obese) but one with high predictive ability.  

If you, like me, are thinking that I don’t implicate diet (by diet, researchers mean the food eaten/daily intake of food—not the “eating less" definition of diet used colloquially) or exercise in a “binary" or “either-or" fashion but in a more nuanced, measured way (like its 60% lack of exercise and 40% excess food eaten that’s to be blamed for packing on the pounds), hold on.  

Researchers also found that a stronger belief implicating excess food as the cause of excess weight was related to a lower BMI. On the other hand, stronger belief in lack of exercise as the primary cause of obesity was related to a significantly higher BMI.  

The biological battle 

It is not surprising that we are fascinated by the discourse on genes—to discover that tiny bundles of DNA have such power is awe inspiring in its own right. What is equally unsurprising is that what we choose to believe is affected by what we read and hear. 

Though dated, a comparison between two national polls conducted in America showed that in 1979, 36% participants believed that heredity is the key cause of being overweight, and driven by increase in media attention over the next 20 years. This figure had jumped to 63% in 1995.  

Indeed, the human genome has not kept up pace with people’s changing opinion. Simply put, science is clear that overeating is the primary cause of obesity—not genetics or lack of exercise.  

However, having read an article or two espousing the latter, people do form uninformed beliefs about how much to blame genetics. A 2014 paper in the Journal Appetite sought to test these beliefs and their influence on consumption and health.  

They found that the more people believed that weight is genetically determined, the less likely they were to believe that they can do anything to influence their weight. More interestingly, participants who were led to believe (by reading an article) that obesity is caused due to genetics, ate more cookies later, compared to those who read an article about other (non-food) related factors influencing obesity.  

Hence, our naïve beliefs about what we choose to implicate as the cause of excess weight have immense influence on what we choose to consume, and how much.  

Science-blind?  

In his book Scienceblind, psychologist Andrew Shtulman calls these naive concepts as intuitive theories or “untutored explanations for how the world works", or in this case, how our body works. Such naïve theories can be a double-edged sword.  

On one hand, they probably encourage us to find more confirmatory evidence for what we believe in (and hence, read/explore more). On the other, they close our mind to the evidence that doesn’t neatly fit in with our premise about how things work. More importantly, these mere beliefs can affect the likelihood of a critical phenomenon—like being overweight.  

The antidote to falling prey to your own naïve beliefs? Simple: beware that you can and be aware so that you don’t.  

Shilpa Madan is a soap and shampoo marketer turned consumer psychologist. Her research interests lie at the intersection of naive beliefs and consumption choices. Having worked with Unilever in sales and marketing in her past life, she now aspires to bridge the academia-business chasm through Serein Insights, an endeavor to demystify and leverage academic research for solving diverse problems for businesses and brands. She tweets at @Shilpa_Madan

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