I was thinking of doing a nice long 30-day fast, but I am a tad worried of the rumored threat of “permanent” drop in metabolism. I don’t like the idea that the human body would permanently drop metabolism from a long fast, and I can’t seem to find any hard evidence for this, but I was curious if anyone had looked into this further and maybe found some evidence either way.
It does seem that if you keep rolling fasts at a max of 96-120 hours, you should be OK.
As your weight drops, your metabolism drops. If you think of food as fuel, a freighter truck is going to burn through fuel much quicker than a prius simply due to its own mass and size.
As you lose weight over your fast, you will need less food by the end of the 30days as you did before. Your metabolism doesn’t “stop working”, it is just proportionally reduced to your body mass. If you were to exercise and build a lot of lean muscle after your fast, your metabolism would increase again as you need more calories to maintain your muscle. However this time you will have less fat on your body than you did before. Hope that helps.
It’s counterintuitive, but extensive studies e.g those cited at length in the obesity code, have shown that concepts like “starvation mode” are a myth, and that in long fasting metabolism is maintained or even goes up after switching fuel sources to fat. An even more surprising result to me was that metabolism decreases were more associated with restricted calorie diets where food is eaten in small portions and often due to insulin related mechanisms. I recommend reading Dr. Fongs book for more details if you are interested
I have before and after dex scans. That show 25 lbs lost. 24lbs fat loss. 1lb muscle… tech kept asking me questions. Never seen this before. He said most people who lose weight have a 4:1 ratio.
Having said that I do 24 hr fasts 3x a week with one or 2 72 hr fasts thrown in a month. I don’t fing long fasts effective for weight loss. And I do light exercise 2x a week and walking. Lots of walking.
Longer fasts are good for other things than weight loss.
Fasting increases metabolism it has been elegantly demonstrated by studies. Low calorie diets decrease metabolism. There is a natural evolutionary explanation for this: if food is low, just move less, burn less, wait it out. If food is 0, increase your metabolism to be able to change your environment, or hunt that gazelle.
I have no hard evidence backing this up but I would imagine it could go either way. If you eat right and exercise your metabolism would go up, but if you sat on the couch all day in a calorie deficit your metabolism would stay down. Your body reacts to whatever is going on around it, very few changes are permanent.
If this was true then nobody would ever fast. Metabolism changes come pretty quick as the body realizes you are in a period where food is lacking. It then shifts when it realizes food is plentiful again. There is evidence that people who yoyo diet can cause havoc to their metabolism. If you look on youtube or google, there are resources about what is called “Reverse Dieting” where you work with a messed up metabolism and slowly raise it by slowly increasing your calories.
I’ve personally done 25 days and not experienced any metabolic problems. You can definitely tell the metabolism slows pretty quickly as you often feel cold easily even in warmer weather. Then once finished, I can always feel things revving up as I am always warm for the first few days. If you do feel like your metabolism is out of whack then definitely check out the reverse dieting resources.
Lifestyle matters a lot here. What I’ve learned YouTube channel is an excellent resource for this. I believe he includes all his scientific references in the description.
Movement whilst fasting will result in conservation of muscle mass whilst a sedentary lifestyle will result in substantial loss of muscle mass which will certainly alter your metabolic state.
Yes, you lose weight so that lowers your metabolism.
Metabolism=how many calories your body burns
Which is largely determined by the size of your body, every part of you needs x amount of calories in order to live. So if there is less of you then you will need less and burn less.
There are a few ways your body will try to save energy while in a fast such as lower your body temperature, make you feel lethargic, and cut down on nervous movements. Once you start eating enough calories these will stop.
Going on personal knowledge and not any studdy here, but the drop in metabolism is probably a result of a loss of mitochondria, so if you work on increasing mitochondrial count/efficiency you can bring your metabolism back up or even increase it.
Honestly idk why this is something people spread without any facts but think about it like this. When you eat less your metabolism drops bc your body sees you are not getting enough nutrients. Your heart slows, you become more fatigue as your body will burn less calories to preserve energy, it’s survival. Once you start to have a steady amount of energy your metabolism will speed up and unless you are overeating you will not gain back excess weight, its survival. I don’t think we would have made it far if we get obese when we are supposed to be hunting to survive.
I have gone on so many fasts and bc I am a bit overweight when I lose the weight and go back to eating a proper amount of calories I typically maintain weight or just gained back a pound or 2.
Please someone tell me if this logic is flawed