I am right smack in the middle of fasting for 21 days and I’ve been using it as a learning tool about my body. I also chose fasting due to claims that it won’t reduce my metabolism in the long run like traditional calorie restriction can.. To preface, I’ve been using tdee and bmr calculations and applying it. I’ve been trying variations of intermittent fasting and I continue to gain weight despite all the application of knowledge. So here I am gathering data froma blank slate.
I did 10 days of fasting with water (needed electrolytes on day 7), coffee and various teas. Nothing was added to the coffee or teas. I lost 10 pound in 2 days - but I was pretty bloated and overfed the day I started. After day 10 I’ve allowed myself to start using nut milks and mushroom hot chocolate. The intake is less than 300 calories a day. Besides the joy of a little taste, it doesn’t make a big difference for me. I am doing very light weights and yoga. I walk 7000 steps a day. Results- between the 2nd to 10th day of fasting I’ve consistently lost 1.5 pounds a day. By day 10 I lost 20+ pounds. Based on urine, I have been deep in ketosis since day 3 and I still am.
After I started taking in 300 calories, the loss has relatively halted and I’m losing less than 0.5 per day. Funny enough, I added the 300 calories because I knew I’d be burning more calories those days and needed energy and wanted to maintain the same deficit. Based on my calorie expenditure calculations on watch tracker, which are about 400 calories higher than the tdee calculations for me as a light exerciser, I burn about 2700-3100 calories a day.
Here are the things I’m curious about and if anyone has insights it would be helpful -
why did 300 calories make my body go from losing 1.5 lbs a day to 0.5 a day even though the deficit is the same (deficit is around 2700)
If 1.5 lbs equals 5,250 Kcal then why would the deficit of 2,700 calories lead to so much weight loss during water fasting even after I’d presumably lost my water weight already?
I am using the fast to also get a sense of whether all these calculated metabolic rates are accurate for me, and now my results are sending me mixed messages.
I’m pondering these questions mainly so I can formulate my lifestyle post-fast.
Female sw 260
Your body stores glycogen in your muscles. When you fast your body burns the glycogen and you lose a lot of weight fast initially especially because the glycogen is bound to water. This is in addition to losing whatever the food in your gut weighed. Weight loss naturally slows over time when fasting but fat burn increases once the glycogen is used up. When you consume carbs again the glycogen is restored along with the water it is bound to so some weight comes back fast. You can figure that you will burn a little less than half a pound of actual fat per day overall with water fasting as you inevitably lose some muscle mass as well.
https://www.leanhigh.com/water-fasting/muscle-loss
You’re not losing 1.5lbs of fat a day. You may be losing that in water or bowel movements etc. but to lose that much fat, you’ll need to burn something like 5200kcal a day without replenishing any of those calories.
HAving said that, it sounds like you’re doing great. I wouldn’t ‘wait to need electrolytes’ though. What’s the idea behind that? Your body needs its salts etc. for your muscles, including your heart, to function. Don’t mess around with that.