top of page

"The Science of Fasting: What Happens to Your Body Every Hour?"

Updated: Mar 17

From the last calorie eaten, a simple guide to fasting (please also refer to my fasting strategies guide).

Dan Raynham the fitness scientist: Fasting guide for ultimate health, fitness, extended lifespan and disease prevention.

Unless you have cultural or religious fasting hours, you are free to fast whenever and however you want. Every day, twice a week, every fortnight, or once a month. You can also choose the length of each fast. The results are proportionate to the quantity you do. If combined with exercise, even more so.

I'm going to lay my head on the chopping block: "In terms of lowest work for maximum benefits, fasting is the only thing anyone should worry about in their eating pattern. Absolutely enormous metabolic and overall health benefits! I do not wish to design another branded "dieting" system. 500 this , catkins that, plate-watchers this, blah blah blah. Diets generate money. That is all. They are difficult, and almost no one ever sticks to them, and let's be honest, dieting is ####### horrible.

Choose how and when to fast to fit your lifestyle. It will allow you to just enjoy and appreciate food! And possibly more of it! I'll tell you some fundamental fasting information and times. Fasting has been understudied in female populations, and there are small variations. I recommend reading Dr. Mindy Pelz's book: Fast Like a Girl.

Dan Raynham the fitness scientist: Fasting guide for ultimate health, fitness, extended lifespan and disease prevention.
Fitness starts inside you at a molecular level. Your body will thank you for fasting!

If you don't want to bother with scientific jargon, fasting immediately reduces fat, stimulates growth, repair, and healing, prevents disease, and increases lifespan. Aim for at least 14 hours. The sweet spot for lowest effort is most likely 16-18 hours. Go for it! Read on for science jargon. The article concludes with a key to the scientific terms.

An example of my fasting "day":

Finish eating 8pm. Sleep. Break-fast next day at 1pm. = 18 hour fast. Then just eat! SIMPLES

4-12 (hours)

Stomach empty.

Blood sugar levels drop.

Insulin production ceases.


Food metabolically absorbed (specifics are activity dependent).

Glucagon lowers to balance blood sugar.

Body 'healing' process starts.

Digestive system torpor.

Human Growth Hormone (HGH) secretion increases.


Body utilises stored fat for energy.

HGH high increase.


Increased fat burning (lipolysis) for energy.


Massive increase in HGH secretion. Possible activation of Heat shock proteins.


Glycogen stores utilised.


Ketones released.


Approximately 300% increase in autophagy.


Immune system reboots.

Inflammation reduction mechanisms increase.

Autophagy 30% increase.


Autophagy at maximum

Dan Raynham the fitness scientist: Fasting guide for ultimate health, fitness, extended lifespan and disease prevention.
Num nums in my tum tums!


HGH: Your body contains this remarkable natural healing and repair hormone. After your twenties, it is greatly reduced. It can be significantly increased with high-intensity training and fasting. The type of instruction I provide can increase it by thousands of percent! My body thinks it is 18 years old. It burns fat, boosts lean muscle mass, and promotes skin and bone health.

Autophagy: The body eliminates damaged cells and regenerates new ones. The SQSTM1 gene encodes the ubiquitin-binding protein p62, which induces autophagy and extends human life.

Insulin: Let's your body use glucose for energy.

Glucagon: Counteracts the actions of insulin by stimulating hepatic glucose production and fatty acids into bloodstream.

Glycogen: An energy store molecule broken down into glucose when needed.

Ketones: Fatty acid released from liver when glucose is low.

Please contact me directly for media enquiries, academic enquiries, questions and links to research paper's. Thank you! ©️ 2021 Dan Raynham.


Don't fast if you have a history of eating disorders. If you’re pregnant, diabetic or have low blood pressure.

4,890 views0 comments


Commenting has been turned off.
bottom of page