I have been fasting with just water and black-coffee and I intend to keep it this way. But I wonder how many days I can go before the lack of protein starts being a problem.
I’m 65yo, M, 78kg / 172lb
Most relatively lean people can survive months without food. The biggest variables being BMR and activity level. For example, if you’re doing heavy labor you’ll burn their your fat stores much faster than if your sitting behind a computer or laying around.
Of course eventually everyone will enter a starvation state once fat stores are depleted. At that point in catabolism the body will start breaking down muscle tissue at an accelerated rate to supply the brain and body energy.
Lets say you’re a lean adult male. You have 15% body fat and weigh 200lbs. That’s 30 pounds of fat = 13,608 grams of fat. Each gram of fat has 9 kcals in it. If your metabolic demands modest that would give you around 50-60 days of energy storage before you started to go into starvation.
People say that they are “starving” when the hormone ghrelin spikes. But they aren’t starving. They feel hungry.
I’m on day 14 of a 40 day fast. I’m not starving.
People can water fast for 60+ days without an issue. Record is like > year, with vitamins and MD supervision. Of course everyone is different and I wouldn’t recommend someone try that long of fast without working up to it.