What does an extended water only fast (5-10 days) do to the body (pros/cons)? I want to try it out to get rid of this inflammation on my face.. and feel really healthy. I am a little concerned with fat/muscle loss though. I know I will lose a lot of water weight.. but will I lose a lot of fat? (I am already as slim as I want to get.) I also don't want to lose muscle.. is that possible?
What does an extended water only fast (5-10 days) do to the body?
A five-day fast and ten-day fast are very different because ketosis increases steeply during that time.
In this answer I'll describe a fast of seven to ten days because of the possibility that it may kill cancer cells. Thomas Seyfried, a scientist who does a lot of research in this area, thinks we need to fast at least seven days to make this happen. Therefore, a five day fast may not be worth the trouble. Seyfried recommends from seven to ten days.
It should be said that no matter how long you plan to fast, you should forget your plan and stop immediately if your body shows signs of distress.
We can look at ketone levels to understand the difference between fasts of different lengths. Longer fasts produce higher ketone levels, as shown in the following graph:
As you can see from the graph, the area under the curve is much greater during the second five days than the first five days. You can also see that ketosis doesn't max out until day 30. It takes a long time for the body to get fully into ketosis.
Your experience during the first few days of a fast will vary depending on whether you are already ketoadapted. If not, you will feel crummy. You will crave carbs.
As the days go on, your brain will become more ketoadapated and your cravings for carbs and your overall hunger will diminish. On long fasts, people aren't hungry. However they think about food all the time -- it's very strange! On my 30-day fast I used to read cooking websites for hours every day, yet I felt no desire to walk to the refrigerator and eat anything. Other people report the same thing.
During a ten-day fast, blood ketone levels rise to about 6 mmol/L which is higher than levels attained on the kinds of diets described as ketogenic on paleo websites.
Your blood pressure will be lower than normal. Your pulse may be lower or higher than normal. Your breath will smell funny. Your tongue may turn white and look furry. Autophagy (absorption of unwanted material in your cells) will increase. Your thirst and urine output will be reduced.
You may or may not feel tired and weak. Some people do, some people don't.
The pro is that fasting is good for your health. It may kill cancer cells. It reduces excess body fat. It promotes autophagy.
People usually fast involuntarily when they are sick because the body turns off our appetites at that time. This may be an indication that fasting stimulates the immune system. On the other hand, it may only be an indication that the body doesn't want to expend energy digesting food.
The con is that you may feel hungry or tired.
We are adapted to fast. In other words, evolution designed our bodies to go without food occasionally for weeks at a time. It's not that big a deal.
but will I lose a lot of fat?
I can't find a published paper that reports the amount of fat tissue or muscle lost. Many published papers report the amount of lipids and protein lost, but it's difficult to convert from one set of numbers to the other because muscles contain both protein and lipids.
Total weight loss numbers are available. In one of the papers referenced below, on an eight-day fast, weight loss ranged from 11 to 18 lbs in a group of 6 individuals. That includes water, glycogen, fat, and muscle.
On a longer fast, as ketosis deepens, the body becomes more efficient at conserving tissue. I lost 23 lbs on a 30 day fast. On an extremely long fast, the average is about half a pound per day.
I also don't want to lose muscle.. is that possible?
Sorry, no. During a fast, your body must destroy some of your muscle to convert protein into glucose to feed your brain. If it didn't do this, you would die.
The reason we go into ketosis is to keep this muscle loss to a minimum. Ketosis provides a substitute fuel for the brain so less muscle needs to be destroyed. We are the only animal on earth that goes into high levels of ketosis. The reason we do this but other animals do not, is because our brains are much larger relative to our body size, and therefore our brains require a much larger fraction of the energy used by our bodies.
Cahill GF. Fuel metabolism in starvation. Annual Review of Nutrition. 2006. 26:1-22.
Cahill GF et al. Hormone-fuel interrelationships during fasting. Journal of Clinical Investigation. 1996;45(11): 1751-69.
Your complexion problem can be solved by not eating any food and flushing out all the toxins you have been ingesting prior to your water fast. Those toxins manifest themselves in different ways for different people.
Or you can clean up your eating habits and eat only meat and fat and ckear up the inflamation that way What that means is you cannot eat any food that pours toxins in your body....meaning no wheat products..meaning no bread, no pasta, no pizza, no corn products of any kind, no crackers, no cookies, no cinnamon rolls, absolutely no sugar of any kind and that includes fruit. Fruit has sucrose and fructose. No beer and pretzels. No eating out because you have no idea what your food was cooked in. It might be cooked in soybean oil, or corn oil, or safflower oil, or canola oil...all neolithic.
Breakfast eat 6 eggs panfried in butter or coconut oil, 1/8 pound bacon, a small yam microwaved til soft for breakfast. No lunch because you will have eaten enough at breakfast to carry you through to dinner. Then a big 16 oz steak with lots of fat around the edges. Some steamed broccoli, or calliflower, or asparagus, or squash or whatever other veg you like...slathered with butter. Prior to the main course, a large leafy green salad with red and green bell peppers, avocados, tomatoes, cucumbers, some crumbled cheese, perhaps some bacon cut up into fine pieces and microwaved til almost crisp...sprinkle on the salad. Dressing for me is Good Season packet of Italian mixed in their hour glass with vinegar and olive oil.
You eat this way for thirty days and your inflamation will abate and you will feel absolutely fantastic. You must drink water...more than you are used to...your body weight in pounds divided by 2 and that equals the amount of water in oz to drink. Many paleos do not drink enough water because they are full all the time and don't realize they need more water. There are reports of lack of water in paleos has resulted in kidney stones being passed...not fun judging by the reports I have read.