Hi there I am a 21 year old M. I weigh 56Kg am 175cm and have a body fat of roughly 12.5%. I run 3 times a week but not more than 4 km. I have been interested in longer term fasting as I hear it has health benefits, however I do not have much body fat and do a fair bit of exercise. Furthermore I have read that it can get dangerous if your body fat drops below 10%. I am training myself to run a 10km run in a few months. And I would like to know is it safe for people who are of healthy weight to fast? Is it safe to do exercise while fasting(and what intensity). Does anyone have further reading that could be useful.
PS: thanks for the help it’s really appreciated :)
You’re looking for managing your circadian rhythms, basically. You don’t need a long fast but you still need to give your body time to remove the oxidative stress you acquired through consuming food. Your body has an internal clock (circadian rhythm) for that.
When you wake up in the morning, your body is prepared to intake food. The hormones & such that you produce in the morning are optimized to help you get food and break it down.
You will see this physiological state again in the late afternoon before the sun begins to set. The body will be ready to eat food and break it down.
After the sun sets, your body is designed to go into a rest and digest mode, and then subsequently into a fasting mode.
During the fasting mode, the body cleans up the oxidative stress that was produced when you broke down food throughout the day, and repairs damage to cells and tissues.
Because of the way we constantly eat, we consider living this way to be a “diet” of sorts, and people usually call it a fast. It usually involves skipping dinner, because dinner is usually eaten after sunset.
You need to maintain body fat, so when you eat, you need to prioritize getting balanced fats & proteins in your food, as well as a source of darkly colorful vegetables that include fiber - like spinach. These contain the antioxidants you will need to start the deoxidation process (particularly in the afternoon when you are in a rest and digest phase but not a fasting phase), and the fiber helps to pack and slow chewed food as it passes through the small intestine, allowing the gut lining more time to absorb nutrients from what you have eaten.
You mentioned cognitive fitness. If that is an interest for you, consider a low gluten diet, because gluten leaks through the lining in your gut and enters the bloodstream (no matter who you are). Different bodies’ immune systems handle this differently, so gluten is a common instigation of the neuroinflammation of your micro glial cells, which can cause brain fog, lethargy, poor memory, poor sleep quality, and make you susceptible to chronic pain, inflammation in the rest of the body, and diseases. (Alzheimer’s may be one such disease, for example, but I think the research on that is still somewhat undetermined.)
Basically - yes, you can “fast”, and it will be good for you, but because you do not have excess stores of body fat to spare, your body is not primed for a long-term fast.
A long term fast will decrease your muscle mass and damage your immunity. In particular - the exercise you’re talking about is not healthy on a long-term fast.
Think of it this way…eating, fasting, cold exposure, exercise - these are all biological “stressors” that are positive to our health. However, when you combine biological stressors, you increase the resources you need to use to manage them. If you don’t have the resources to respond to your body’s needs, your body will prioritize the parts of itself that are most important to your survival, and neglect the rest.
There is basically a stress threshold. Once you pass it, you start withdrawing from the biological bank account.
So if, for example, if you fast while sick, you’ll usually become more sick and the duration of your sickness will be a lot longer. The body is already stressed by fasting - now it has to fight of a sickness at the same time. Where is it going to get the energy and resources for that?
You are constantly giving your body stress in the form of exercise. You also have very little in terms of saved resources, and fat is a critical component for your body - it’s needed for your brain (cognition) and organs, your skin, joints, muscles, and immune system. Without those resources, you’re basically living biologically “hand to mouth”. You don’t have wiggle room.
So if you have such low body fat, you don’t want to over stress your body because you simply do not have the resources to give it.
However, we are all built to withstand food withdrawal from dusk to dawn. That is something your body is prepared to manage, and as long as you are eating enough fat and protein during the day to compensate for your metabolic demands, not eating between dusk and dawn should positively impact your body and mind.
Particularly if you don’t consume high amounts of gluten. Again - gluten is bad for everyone.
I recommend sweet potatoes for your carbohydrate source. For protein and fat, make sure you eat the yolks when you eat eggs, because they have the choline needed for your muscle health, and try to balance the consumption of meats that have fat with fish that have fat, because this provides you with the fatty acid diversity you need to service the body properly.
Look videos of Jason Fung maybe he mentioned thin people. He wrote a book about fasting so I’m sure it’s in the book. It is excellent for mental clarity. You can gain all the benefits trough low carb high fat diet.
I was in your same boat 10-15 years ago. Build up slowly. Before you break the fast do a workout but don’t workout while on the fast. I tried working out while fasting and it jacked up my metabolism for a couple years and didn’t give me any of the cognitive or health benefits. I had a low body fat and built up to a 20 day water fast. Just figure that it takes about 1 to 2 times the same amount of days that you were fasting to regain the amount of muscle that you will lose for anything over 3 days. Anything 3 days or less, you have enough glycogen in your system to not lose any muscle once you get used to it. And I feel like working out before breaking the fast trained my body to keep the muscle during the fast more. No evidence for that though. My body could have just gotten better at using fat and keystones over time and that’s why I got better at keeping the muscles. But my first couple fasts were only a day or two and it seemed like my muscles deflated quite a bit and took a little longer to build back up. But once I got used to it, I didn’t lose anything if it was under 3 days.
You need fat for more endurance or need to load up , if you are trying to achieve autophagy benefits you should already be getting those anyway with your cardio as well. Fasting is great but can’t be a thing that’s a dairy routine if you are super athletic as you can also get huge health issues for too low body fat. I’ve used nootropics for mental increases and had great success. I still fast quite a bit but not more than 3-4 days a week but my body fat isn’t no where near as low as yours. https://www.mensjournal.com/health-fitness/15-negative-effects-having-low-body-fat-percentage/amp/