Body Fat set point theory is a widely accepted theory of metabolism. It suggests that each individual person has a level of body fat where their body naturally sits, and the body defends that level in an attempt to maintain it.

Everyone has a different set point, as well. If you’re a 190 lb (86kg) man and have weighed the same for over a decade, and your body fat has been sitting at 16% for that decade, it’s safe to say your body might be a fan of that. Factor in genetics, nutritional habits spanning a lifetime, activity, and everything else you’ve done, and it makes for a distinct variable for us all.

I believe that this set point is largely controlled by the hormone leptin, which response to changes in the size of the adipocytes (fat cells). Think of leptin as your body’s adipose tissue thermostat. A thermostat controls the temperature of the room and keeps it at a set point. If the temperature drops below the setpoint, the heater kicks on and raises it back up.

When the temperature rises above the setpoint, the air conditioning turns on and brings the temperature back down. Leptin is like that thermostat.

The body fat setpoint is sensed by the size of the individual fat cells. As the cells start to shrink during an energy deficit, the adipose tissue cells reduce their secretion of leptin. This reduces metabolic rate (calories out), increase hunger (calories in), and tries to drive the body back towards the setpoint by swinging the body’s caloric balance in a positive direction.

During a caloric surplus, fat cells expand, and leptin secretion increases, which increases metabolic rate, decreases hunger, and drives calorie balance in a negative direction to bring the body back down towards your body fat setpoint.

The defense of set point is so powerful that even after a prolonged diet, your body will fight to bring back your adipocyte size to within a nanometer of its original start point months previous.

By now, I’m sure you’ve known someone (or yourself) who has crashed dieted for several weeks to lose 5 to 10 kg (10-20 lbs) to be “vacation-ready,” only to go on a “food orgy” vacation and gain it right back within a few days. Or someone who dieted for nearly a year to lose 20kg+ (50 lbs), only to go back to eating the way they did previously and gain it all back in less than half the time.

Further, many people who have dieted and lost a significant amount of weight (>5% of your body weight) may have noticed that weight loss was easy at first, but after a certain period, it became much more difficult not only to lose more weight but simply to maintain the weight you lost.

You may even begin to experience increased hunger which makes maintenance and further weight loss harder. Sure, it’s a cliché, but there’s some validity to it. If you’ve been in a prolonged calorie deficit, your FAT CELLS (adipocytes) shrink, leptin secretion decreases, metabolic rate slows, hunger elevates, and your ability for fat cells to assimilate nutrients will be enhanced.

This is improving your body’s efficiency to store energy (fat). So when you consume a lot of energy, you are better able to capture it and store it as body fat, driving you back towards your set point.

One of the central ideas 1 want to hit in this blog series is that every time you diet (eat in a caloric/energy deficit), you are activating the body’s self-defense system. The more you attempt to diet, the stronger the signal to your body to strengthen this defense system.

I believe (based on data) this is why people who diet more often during their life are more likely to gain body fat over time instead of losing it long-term. It’s not that dieting makes people fat; of course not. Someone can’t gain fat in an energy deficit, because that would defy the laws of physics.

It’s because they diet repeatedly and interrupt each diet by regaining the weight more rapidly than they lost it. Thus they are activating this self-defense system repeatedly. Then, when the diet is “over” and they can no longer sustain the energy deficit, they regain the fat they lost, usually relatively quickly, and often add more fat than they lost in the first place.

In this way, the body has defended against famine and further protected itself against future potential starvation.

Finally, people who engage in this chronic weight cycling/”yo-yo” dieting for months, years, or even decades are further potentiating this self-defense system every time they do so.

Therefore, when I discuss any potential fat loss diet in this Blog Series, the emphasis will always be on what is sustainable. Success is only successful if you can sustain weight loss.

Therefore, any form of diet you can’t sustain ought to be banned from consideration as a long-term solution.

End of Part 5

to be continued