Everything in life acts in cycles; night/day, winter/summer, life/death etc. A cycle consists of oscillations with peaks and slopes - this is generally how your body functions most effective, not through constant peaks or slopes but through lots of variation.
Our society goes through cycles of war and peace time, our body goes through cycles of growth and loss. It is a truth many of us unconsciously know about - Yet we often act counter to that truth.
The usual recommendation when it comes to progress is 'Consistency is key', yet nothing in life is consistent. When looking up health tips you'll often see recommendations such as; eat that amount of this, this product and do that. What all of these recommendations have in common is their chronic nature, keep doing the same thing no matter the circumstances.
In my opinion this chronic nature of acting will result in overreliance, injury, sickness and general fatigue. I might even go so far as to say that many of the illnesses we endure as a society are due to the constant tension or lack of varied stressors- I think we can do better.
How to incorporate cycles and variation into your life
The used methods will have to vary from person to person as the cycles should be in relation to your current life. Every method will have a different effect depending on the person and stage of their life.
What remains unchanged however are the principles in regards to these cycles, one of them being Complexity VS Simplicity - More on that later.
Every domain of your life can be exposed to cycles; having focus heavy days during your work and off days right after, training hard a few days of the week followed by a period of rest or periods of feasting and periods of fasting. Utilizing this strategy will cause short-term stress, allowing you to adapt directly followed by a recovery phase.
Complexity VS Simplicity
The above mentioned principle is particularly effective for your metabolism and diet, but it can be used for any situation in your life. A period of stimulated growth followed by a period of reduction where you are forced to become more efficient
Fast vs Feast
When your goal is to have a healthy and functional body, my general recommendation is to have a period of feasting and a period of fasting. During the former you'll want maximum stimulation and growth - building muscle and other tissue. Subsequently this phase will be followed by fasting, a phase where you kill off the weak cells - recycling of broken tissue and forcing processes to become more energy efficient.
Sped up metabolism VS Efficient metabolism
Metabolism in simple terms is the synthesis of readily useful energy for the body, this happens through conversion of sustenance and/or tissue into something we call ATP (an energy unit used by the body).
During periods of growth your body will learn to release energy faster and in turn increase the usage of fuel sources. This often goes hand in hand with mouth breathing, exercise like sprints and increased food intake.
During periods of efficiency your body will learn to streamline chemical reactions within the body and increase the conversion from sustenance into useful energy. Inducing periods of efficiency can be done through; forced nasal breathing, endurance workouts, decreased food intake and longer stressors.
What I do personally
When it comes to fast vs feast I have days where I eat throughout the day, these are often days with little stress and easy to perform tasks. And there are days where I eat nothing or just one meal to starve my body slightly.
To make my metabolism more effective I tend to incorporate workouts focussed on intensity allowing all the metabolic processes in my body to speed up, and workouts with slowed down breath to force my body to widen my arteries and veins as well as dealing with less oxygen.