Obesity and Evolution

How do we get fat? When the calories in is more than the calories out, our body stores up the extra calories as fat. Fat is not all evil. For the early human beings living in the savanna, fat helps them survive famines and keeps them warm. Without fat, human beings may not even exist today.

In our modern days, with the abundance of food all year long, our body keeps on storing up fat but never has a chance to use it up. Our body is not adapted to deal with such huge amount of fat, it deposits the extra fat wherever possible, in the liver, in the blood vessel, beneath the skin, around the internal organs etc. That leads to fatty liver, cardiovascular disease, stroke and increased risk of diabetes. The once good fat becomes evil and makes us sick.

Obesity is not a disease itself. It is a condition that puts us at risk of many chronic diseases. These diseases can seriously affect our quality of life and may even shorten our lifespan. The negative impact of obesity on health is well-known to the public. Not many people would be willing to be obese except in countries where fat is still considered a sign of prosper and beauty, such as Tonga, Fiji, Nigeria. Then why on earth there are so many people obese and the figure keeps on going up all around the world?

The answer is very simple: because we cannot control our body.

Millions of years of evolution has taught our body to store fat for survival. That’s why high calorie food is so appealing to us. High-fat and high-sugar foods are so popular not only because of the advertisements from food industry, but also driven by the force of evolution: calories are scarce, store it whenever you can. If we let our body to choose what we eat, we can easily become a fat factory.

To make it worse, our body naturally resists weight loss because that can decrease our chance of survival in the wild. That’s why it is so difficult to lose weight. Participants of weight loss programs usually lose weight at the beginning but always regain their weight not long after. Constant fat storage + minimum weight loss = obesity.

For millions of years, our ancestors were living with scarcity of food and constant famine. We have created a world full of food that never exists in the natural history, in as short as 50 years. Evolution simply cannot catch up with the changes. The old “store fat whenever you can” mechanism is still in use. Maybe in several hundred years, we will develop a mechanism to limit calorie intake or to get rid of extra fat naturally. But for now, we are suffering from the imbalance between development and evolution.

The driving force of evolution is to keep the species propagate. Since obesity is severely affecting the fertility and mortality of human being, evolution will for sure find a way to fight against it. But it needs time. This is a natural process that may take hundreds, if not thousands, of years. But eventually, it may develop some mechanism that is out of our imagination.