HOW Intermittent Fasting or Time Restricted Eating help our bodies and brains
How do we explain the health benefits that IF has on our bodies and brains? One way is that a “metabolic switch” is flipped during fasting.
While continuous calorie reduction and IF have many of the same health benefits, IF might have a different biological mechanism at play. Some research suggests that I.F. might “flip” a metabolic switch.
Here’s how it works.
After we eat our bodies use carbohydrates (e.g. glucose) from our food for fuel. If there is extra left over, then it’s stored as fat for future use.
With fasting, just as during extended exercise, our bodies flip from using glucose (and storing fat), to using that stored fat and ketones (made from fats) for fuel. Sometimes called the “G-to-K switch,” (glucose-to-ketone) the ability to flip what our bodies use as fuel (between glucose and ketones) is called “metabolic flexibility.”
It’s thought that we, and many animals, evolved to have this ability to survive short periods of fasting from when we were hunter-gatherers. There were times when people didn’t have a lot to eat, but they still needed to survive and think clearly enough to successfully hunt and gather food. This can explain why our bodies and brains don’t necessarily become sluggish when we’re fasting. It makes a lot of sense, although it has yet to be tested in current-day hunter-gatherers.
This metabolic switch can explain some of the health benefits of fasting.
When our bodies prefer using fats for fuel, the body starts burning our stored fat. This is how IF helps with overweight, obesity, metabolic syndrome, and type 2 diabetes. When the body uses fat for energy this decreases the amount of fat in the body. Reduced fat reduces weight, and health benefits from weight loss (like lower blood pressure and insulin resistance) are felt.
This “flipping” of the metabolic “switch” happens after the available glucose, and the stored glucose are depleted. This is anywhere from 12-36 hours from the last meal, depending on the person.
At this point the fats in our cells start getting released into the blood and are metabolized into ketones. These ketones then go to fuel cells with “high metabolic activity” – muscle cells and neurons.
Since the body is burning fat and using ketones to fuel the muscles, IF can preserve muscle mass. Some studies of IF show that it preserves more muscle mass than regular calorie reduced diets do.
The other high metabolic activity cells fueled by ketones are neurons (in the brain and nervous system). IF helps our brains because when our neurons start using ketones for fuel, it preserves brain function and increases brain-derived neurotrophic factor (BDNF) which is very important for learning, memory, and mood.
BDNF also helps enhance synaptic plasticity (changes in our brain that help with learning and memory) and allows our neurons to better resist stress. These are all improvements in brain function, and some animal studies also show improvements in the structure of the brain too. For example, new neurons are produced in the hippocampus (the part of the brain important for short- and long-term memory) in animals who IF.
According to Anton, 2018:
“In these ways, events triggered by the metabolic switch may play major roles in the optimization of performance of the brain and body by IF.”
Whew! That’s a bunch of good science, I guess sis knows a bit about this stuff.
Here she is (I guess it works!).
Next time I blog on IF, I’ll sum up the conclusions, and share all the science links I found on all of this.