I am wondering if there is any reason why I wouldn’t want to do an extended fast from a lower starting weight (140lbs)? Sorry if this is a silly question. From my understanding, I would only run into issues if I depleted my fat stores or neglected electrolytes.
Well it really depends on how much weight you need/want to lose. Example if your starting weight is 140 and your a male you should try not to go below 10-15% body fat(getting sick at sub 5% can mean death from lack of body fat). If your a woman then the body fat % are a bit higher. Btw those numbers are like all your abs and veins showing crazy well “normal” for a male is around 20-25% for men for women if i remember correctly is around 24-29% with athletic slightly lower. Basically at around .5-1.5 lbs of body fat lost a day you may be going to far with a extended multi day fast. If a good weight is 130 and your at 140 then a 30day water fast may kill you or get close. Look up your basal metabolic rate and then divide that by 3500 and that is how many lbs a day roughly you can expect to lose per day.
If your not worried about going too low(say a good weight for your height/build(body fat % is better because it doesnt matter about weight(you can be 140 and jacked 4’8” for example) muscle weighs alot) then you can do a extended fast.
Just remember your surviving on fat stores; out of fat? Dead.
Because you still need energy to function? Depending on your height and gender 140 is a perfectly healthy weight. If you’re a tallish man then it’s underweight. When you don’t get enough energy your body consumes its fat stores, if you don’t have enough fat stores it consumes muscles. If you’re a man you need about 12% body fat at the absolute lowest just so your organs function correctly. Ideally it should be around 18-22%. So lets say you’re an average man of average height, so 5’8. At 140lbs, assuming you’re of average build, this means you have a BMI of around 20%. That means you have a healthy BMI, and a multi week fast will put you into the underweight category. Why is that bad? Your organs are made of fat. Your brain, liver, kidneys, and so much more need lipids to work correctly.
Now if you’re a 6 foot tall man then this is even more dangerous. However, if you’re like 4’10 then it couldn’t hurt.
In short, fat is not bad. Having the correct amount of fat is good. Going over or under is bad.
If you do not have much fat to lose, you will have a greater loss of muscle. Apparently the body can only extract a finite amount of “calories” from fat and will be forced to dip into muscle stores to maintain energy. I have definitely experienced this personally and I’m sure many others have as well.
Just for fun? Like a physical challenge? Or do you have a goal/objective you’re trying to hit? I guess it would also depend on how long you wanted to do an extended fast. If you’re shooting for a very low body fat number might be helpful, but you’ll also likely lose lean muscle tissue as well. You’d need a good plan. First time fasting your body will go through the mineral flushing and replenishing with sufficient electrolytes can be a challenge.