There is a natural body-alone-weight system of training called Calisthenics. Those who are masters at it point the fact that all the body needs is some direction on where to work out.
No need for a lot of repetitions nor hard-time "no pain no gain bs" stuff.
All the body needs is to activate those parts by inducing some smooth physical movement, and it gets the message where and how to work and develop.
The same goes with fasting.
I have tried myself long, more than 18 hours of fasting sequentially to try it on myself and see the results. But the answer was much more devastating than healing.
The reason is because when you go for such a long time without input, the body at first burns, heals and works in the right direction - for the few beginning hours and days, but then it goes on to spend itself to the point of such weak muscle-connections that even a walk can cause problems.
The reason why I am saying this is because of a reflection from yesterday as the first day of fasting during winter-time, the first day of the Natural Year.
I noticed immediately my body working in the right direction, the improvement of my sense of being, without any burden at all.
All the body needs is few hours. Do that for 10 days, and voila.
Also, there is a recent finding of immune system boost by only fasting 3 days.
So, when God says, it is better for you - if you knew. This is it.
Let's say we're in the southern hemisphere, where there is the greatest daylight during the winter solstice of the part above equator. Few days, 10 days, are enough.
The beauty of the truth is that its applications are the same. Calisthenics and Fasting have the same approach:
Letting the body develop, heal and regain itself the natural way.
For struggle, are enough your personal tests of this life.
2:185...God wants to bring you ease and not
to bring you hardship;
Praise be to God. The Lord of all that is.
Peace,
R.
P.S. And remember to fast from your thoughts as well. That's the main un-needed food.