December 13, 2019 | By Fastwell Team | Fasting
These days there is a lot of buzz about fasting. Almost everyone has a friend who regularly skips breakfast, eats one meal a day or will even go for days without food. But, what exactly happens in the body when you fast? And, what “breaks” your fast?
We talked with top experts (both researchers and practitioners) and poured over dozens of publications to understand the physiology of fasting. To put it simply, we learned that the “fasted state” is really a set of biological mechanisms that are activated when you stay below thresholds for intake of macronutrients and calories.
With this understanding of what fasting is and how it impacts the body, Fastwell has designed its products to have the right thresholds of calories, macronutrients and micronutrients to help you optimize your experience and outcomes with fasting. Our products help you fast safely.
Without further ado, here are the details about these biological mechanisms and the thresholds that govern them.
The first thing to happen during fasting is the body switches from burning glucose to burning fat. This happens after a period of about 12-24 hours of carbohydrate restriction (<20 g), which causes blood insulin to drop and ketone bodies to rise. A ketone level of 0.6 to 3.0 mmol/l is considered “nutritional ketosis”. To accurately test your ketone levels, you can use a blood ketone monitor.
Autophagy is a process by which our bodies eliminate damaged cellular components. It’s hypothesized that autophagy is activated after 24 hours of consuming less than ~700 calories and less than 30 g of protein (or 35 g of plant-based protein).
Stem cells play an important role in cell renewal and healing. As we age, stem cell rejuvenation slows down which contributes to declining organ function. Improving stem cell turnover can be protective against diabetes and cancer. Several animal studies have given indication of stem cell rejuvenation during fasting.
Growth hormone helps maintain tissues and organs throughout life, unfortunately production begins to slow in middle age. Fasting has been shown to be one of the best ways to increase HGH naturally.7 See a great breakdown of the research on increased HGH through fasting here.
Microbiome health is becoming more understood as a key factor for metabolic health. It is hypothesized that fasting helps the microbiome by allowing gut bacteria to rest from digestion. This thorough article on microbiome and fasting quotes “Germ Guy” Jason Anthony Tetro, a Visiting Scientist at the University of Guelph as saying “We are just now starting to determine whether there is any impact on the human microbiome during fasting.”
We worked with Dr. Krista Varady of University of Illinois-Chicago (one of the top researchers of fasting!) to understand how the biological mechanisms of fasting might impact metabolic health and chronic disease. (See sources 8-12)