Go to the page content
About obesity Barriers to weight loss

Our biology and the modern world: How environment affects our health

The world we live in and the food we eat have dramatically changed over time, but our biology has largely stayed the same. It can trigger us to believe that we are at risk of starvation and make us look for food rich in energy, salt, fat and sugar.

5 min. read

Think about our everyday life: most of us commute by car or public transportation to work. We have elevators and escalators to take us where we need to go without a drop of sweat. Office jobs and city life often mean that we have to sit more and for extended periods of time. We are surrounded by lots of tasty food and drink that we have easy access to. And there’s so much to worry about and catch up on—whether it’s at work, in our private lives or on social media. So, we sleep less and stress more.

But few of us are aware of how all these things are linked to obesity. In order to understand this, we need to travel back in time.


Our environment 50,000 years ago

“Eat or be eaten!” Imagine living 50,000 years ago in the Stone Age. All our ancestors cared about was chasing calories through hunting, gathering or fishing. That, and avoiding becoming the meal of the day for large predators.

Food was scarce, so being well fed meant a higher chance of survival and also a higher chance of reproduction. The key to success was getting a hold of food with a lot of fat, sugar and salt. That’s why our bodies have learned to look out for and favour energy-rich foods to get through periods of famine.

"We have created a biology–environment mismatch, as the human weight regulation is unable to evolve fast enough to keep pace with the environmental change."

--Lee YS. “The role of genes in the current obesity epidemic.”

Life changed—our biology did not

You might now think that we must be quite different from our ancestors. But the systems that helped them survive are still active in our bodies today and often work outside our conscious awareness.

The weight of the modern world: How our environment affects our health

Food manufacturers, supermarkets, restaurants and fast-food chains have picked up on our food preferences. They now offer a huge variety of cheap, delicious and energy-rich foods that combine salt, sugar and fat. This is a powerful combination for our senses—far more powerful than our brains have evolved to deal with. That’s why it’s hard to resist the enticing smell of food we are now surrounded by.

We shouldn’t be surprised when we super-size our takeout order or fill our shopping cart even though we are not hungry. Our ability to resist these deliberately tempting foods is determined by a range of factors, including genetics, and varies from person to person.

So, the global rise in obesity is not the result of a sudden loss of willpower. Instead, weight gain is understood as a natural reaction to living in an environment that has changed faster than our species has been able to adapt to.

Nearly 2/3 of Canadian adults are currently overweight or living with obesity.

--Government of Canada
Fruit bowl


  1. Appelhans BM. Neurobehavioral inhibition of reward-driven feeding: implications for dieting and obesity. Obesity. 2009;17:640-647.
  2. Morris R. Stranger in a strange land: an optimal-environments account of evolutionary mismatch. Synthese. 2018;1-26. 
  3. Guyenet S. The hungry brain. Outsmarting the instincts that make us overeat. New York: Flatiron;2017.
  4. Berthoud HR. Interactions between the “cognitive” and “metabolic” brain in the control of food intake. Physiol Behavior. 2007;91:486-498. 
  5. Harvard Health. Why People Become Overweight. Accessed May 28, 2023. https://www.health.harvard.edu/staying-healthy/why-people-become-overweight#:~:text=If%20you%20consume%20more%20energy,throughout%20your%20body%20as%20fat
  6. Lee YS. The role of genes in the current obesity epidemic. Ann Acad Med Singap. 2009;38(1):45-3.  
  7. Cohen DA. Obesity and the built environment: changes in environmental cues cause energy imbalances. Int J Obes (Lond). 2008;32(Suppl 7):S137-S142. 
  8. Government of Canada. Tackling Obesity in Canada: Obesity and Excess Weight Rates in Canadian Adults. Accessed July 6, 2023. https://www.canada.ca/en/public-health/services/publications/healthy-living/obesity-excess-weight-rates-canadian-adults.html 


Check your BMI with a BMI calculator

Body mass index (BMI) is an important measurement when it comes to understanding your weight. While it should not be used to diagnose obesity, it can be used as a screening tool to classify your weight.

Find your BMI and health risks

Metrics Imperial
Metrics / Imperial
Was this valuable for you?

You might also like