Weight Loss (Controlling Body Set Weight) | Jason Fung

The body set weight acts like a sort of thermostat for body fat percentage.

Let's think about the concept of how a thermostat works.

What you do is you set the thermostat and for room temperature, for example.

And if it's too cold outside, the room gets cold and the thermostat will activate the heater to bring the temperature up to the proper setting.

If it's too hot, then it's going to turn on the air conditioning and bring the temperature down.

In either case, what you do is you try to keep this comfort level.

And this applies also in physiology.

It's the concept of homeostasis.

That is, when things get too hot on your body, you're gonna cool it down and you do that to sweat.

When it gets too cold, you're gonna shiver and bring the temperature up.

It turns out that homeostasis also applies to the concept of body fat.

And the reason is that the body fat percentage is a hugely important factor in survival for wild animals.

If you think about it, an animal that has too little body fat compared to a normal animal is not going to survive because body fat is a store of energy or calories.

So if it doesn't have enough body fat, there's only a limited time that it can survive before it dies of starvation.

And if it has too much body fat, well, it's going to be slower.

So it's going to find it harder to get food.

And at the same time, it's going to be more likely to get eaten.

So therefore, in the wild, the body fat percentage is a very tightly controlled measure.

And this applies to humans as well.

If you look at the studies over the last 50 years, we've well known that the body fat is not controlled just by the calories you take in versus the calories you take out.

There's a body fat thermostat, which is sometimes also called the body set weight.

This is a study done in the 90s, so almost 30 years ago, which clearly demonstrates this.

What they did is they took a group of people experimentally, gave them a shake and fed them so much that they gained 10% in body weight.

Then they looked at how much energy that these people were using in a day.

When they gained weight, their bodies increased their caloric expenditure by almost 500 calories a day, which means that they were trying to burn off all of the excess calories that they were taking in.