The Cause Of Obesity Part 1: Big Picture

We are at war with obesity and we are losing. It is time to fight back. But, before we can beat the enemy, we must understand the enemy.

Back when we used to hunt lions, breakfast, lunch and dinner was not guaranteed. As a safety measure, the human body became quite good at utilising as much energy as possible from the food we ate. Any excess energy was stored away as fat to be used for a rainy day.

The problem. We don’t hunt anymore.

Instead of hunting, we google “Chinese restaurants in Melbourne”.

Instead of the jungle, we have Coles.

Instead of starving, two thirds of the population are overweight or obese.

Simply put, obesity comes down to a problem of energy balance and storage. More specifically, a problem with fat storage. It seems many of us are hoarding fat for a raining day. It never seems to rain though…


Let’s have a closer look at a well known but, deceptively simplified equation.

Energy IN < Energy OUT = Weight loss

Energy IN > Energy OUT = Public health crisis

 Key points about Energy IN (i.e. what you eat)

1. It is not a simple matter of willpower.

“People are obese because they have no will power”. Oh dear.

The process of eating and how you bring yourself to eat, is more confusing than why the creators of The Simpsons are STILL producing new episodes. The whole system of balancing the energy that comes in and goes out is largely controlled by the endocrine system and the nervous system. For simplicity, let’s call these two systems the “Dream Team”. Broadly speaking, the Dream Team play a part in influencing your appetite (your “Energy IN”) and how you burn energy (your “Energy OUT”). In theory, everything is kept in balance like a seasoned Doga expert (not a spelling error, look it up and thank me later). Unfortunately, the Dream Team gets overwhelmed easily, the balance is shifted in the wrong direction and you get something called the obesity epidemic.  This is a very simple version of something very complex. In fact, some of the main players are named things like leptin or neuropeptide Y or alpha melanocyte stimulating hormone. Hmmm, perhaps there is more to it than just “willpower”?

2. There is a psychology behind when, why and what we eat.

Ideally, you should eat when you are hungry and stop when you don’t feel hungry anymore. Unfortunately, we are not robots and most of us don’t just eat when we are hungry. We eat when we are bored, stressed, anxious or even depressed. For many, eating and in particular, overeating, is a habit. It is ingrained into one’s subconscious being. Interestingly, there is a field of science dedicated to the science of habits and more importantly, how to change them. I talk about this in more detail here.

3. The environment is “obesogenic (obeso- obesity, genic – causing).

We live in an environment that makes it easy to become obese . Ever think about the unnerving ability of a McDonald’s to pop up within 5 minutes of wherever you are at any given time? Keep an eye out for advertising giants bombarding you with not so subtle reminders to buy their latest products. There are certain countries in Africa that don’t have access to clean water but have access to Coca Cola. I will let that marinate for a bit.

4. Genetics play a role.

Something in your DNA, whether you like it or not, increases or decreases your chances of being obese. In studies, with adopted children, they have shown that these children often resemble the weights of their biological parents. Identical twins, even if they are brought up in separate households, often show similar weight trends as well. Interesting right?

5. It is hard to know what is truly healthy and what is unhealthy anymore.

Too many fad diets. What in the world is the “wine and eggs diet” or “the grapefruit diet” or the “eat a banana at 1pm diet”? One of these is made up. All of these are absolute [insert swear word here].

Nevertheless, there are at least a few hundred different schools of thought on what is healthy these days and each have a relatively strong following. Hence my quest to find and expose the truth. It’s hard to expect people to eat healthy when many people, even in health field, are not sure or not up to date with the latest evidence.


Key points about the Energy OUT component (i.e. not just exercise)

1. Exercise only contributes to 5-10 % of your energy output.

Most people instinctively know that weight loss is rarely possible without changes in diet. This is why! Theoretically, despite what is discussed above, you have full control over what you put in your mouth and therefore, 100% control over the Energy IN component. Unforunately, you only have 5-10% control over your Energy OUT component. This is why you have to run for an hour to burn off one Nutella donut.

2. 90-95% of your energy output is outside your control.

There are 3 main components here. Basal metabolic rate refers to the energy used to keep the basic functions going (i.e. keep the heart beating, the lungs breathing and the brain…um…thinking?). This accounts for 70% of energy output. The remaining 20-25% comes down to the energy needed to digest, process and store food as well as something called adaptive thermogenesis (super complicated but may be a reason why it easier to lose weight at the start of someone’s weight loss journey than towards the end).

This stuff is completely out of our control. It is dictated by genetics, the Dream Team (of course) as well as a whole heap of other stuff that some people dedicate their whole lives to try to understand.


  • Obesity comes about when the balance between Energy IN and Energy OUT is out of whack.
  • This balance is super complicated and requires 5-7 pHDs to fully understand.
  • You can potentially control 100% of your Energy IN but only 5-10% of your Energy OUT.
  • The writer of this post is handsome and considered a good catch by countless Sri Lankan aunties.

Consider this post an overview of what’s to come. I will try my best to make sense of this enormous and confusing topic. It is crucial that everyone has a good understanding of this topic because it could literally add quality years to your life and the lives of your kids.

Please share this post and let’s spark a conversation about obesity and what can be done about it.

Related posts:

The Cause Of Obesity Part 2: Changing Bad Habits

The Cause of Obesity Part 3: Eating Carbohydrates

The Cause of Obesity Part 4: Eating Fats

Weight Loss Solutions: Sustainability 

The whole (food) does not equal the sum of its parts


Take care of yourself and everyone else,

Dr G