So far we’ve learned about the major types of macronutrients, the two types of metabolism that your body can run on, and why these are important factors to consider for survival. In terms of advice the scales are leaning pretty heavily towards a fat based diet instead of one based on carbohydrates such as grains, flour and sugar.
To this point, we have been focusing mainly on the effects of carbohydrates on insulin in the body. But today, we’re going to take a look at an important hormone that has recently entered the spotlight in nutritional science: leptin.
What fat mice and night shift workers have in common
In 1950, researchers were in the process of breeding lab mice for different traits. One of the variations was an incredibly hungry mouse that would eat until it was physically unable to. All of these mice would eventually become obese, giving them the appropriate nickname of ‘obese mice’.
It took over forty years until the mystery of why the obese mice would eat so much was solved. At Rockefeller University in 1994, a researcher by the name of Jeffrey Friedman was able to isolate a protein that, when injected to the obese mice, would allow them to eat normally and return to normal weight. This protein was a combination of 167 amino acids called leptin.
The way that leptin works is by controlling the body’s hunger. When you experience hunger, you will continue to eat until you are ‘satisfied’, but the amount of food that will allow you to be satisfied is determined by leptin. The reason obese mice ate the way they did was because they were genetically unable to either produce leptin or have functioning leptin receptors, and thus kept eating to satisfy their hunger. This sounds like a cool science story but the applications to survival foods are huge.
In nature, leptin is the perfect feedback loop to maintaining a healthy bodyweight. It is produced by fat cells themselves, so in theory, having more fat cells would make one feel less hungry. Fat levels would go down to normal and no one would be at an unhealthy weight. However there are literally hundreds of millions of human examples to prove that it isn’t the case today.
The reason this happens is leptin insensitivity. From having chronically high levels of leptin, leptin receptors in the brain cannot tell when leptin levels are high or low. Essentially, this is what happened with the obese rats – with no ability to tell when they are satisfied they would eat until they could not. This would be devastating in a survival scenario, either causing unnecessarily high food consumption or being incredibly stressful psychologically from constant hunger.
Thankfully, there is a solution for this. Low carb diets have been shown to restore leptin sensitivity in two ways. First, they lower blood triglycerides which makes it easier for leptin to reach the brain. Second, they have the effect of reducing bodyfat which contributes to chronically elevated leptin. In addition, several carbohydates like fructose and wheat have been shown to interfere directly with leptin receptors.
You reduce carbs, you reduce leptin insensitivity, you reduce hunger.