If less than 24 hours, there is probably no need for supplementing for fasting purposes. If you feel able to, you can just jump into OMAD (one meal a day) without too much difficulty. If that does prove too much, just back it down to 2MAD. I would recommend listening to the Fasting Method Podcast.
There’s 2 styles of fasting - intermittent fasting (IF) and extended fasting (EF).
With IF you get into a pattern, normally a daily pattern, of eating in a set window. 16/8 is the most common. You refrain from eating for a 16 hour period every day. And eat in an 8 hour window. For example - eat between noon and 8pm, fast 8pm to noon next day. This is good way to start.
Other popular IFs are 18/6, 20/4, and 23/1 (often called OMAD - meaning one meal a day). This is actually a very effective lifestyle. I’ve done OMAD for 4 years and really enjoy eating like this. Don’t count calories - just eat a heathy meal to full every day.
The EFs are longer. As short as 24 hours. 48, 72, 100 hours are not uncommon. 7 day, 14 day, 30 day, 40 day. They can get quite long. You do the longer fast, and then recover. Before maybe deciding to do another. Some people do rolling 48s or even rolling 72s. With with a meal in between.
The good thing about IF is you’re doing the same thing every day. The body is more than capable to fast up to a day. No special electrolytes or dangers. It’s also quite effective for weight loss.
The EFs get more technical. Your body needs certain electrolytes (like salt) regularly. It’s neurologic - you can’t survive without these. Water intake is also very important. When the fasts get long, breaking the fast gets trickier. Your stomach acid losses acidity when not eating. So you have to be gentle. With longer fasts it’s called refeeding and can take days to accomplish. Breaking a longer fast wrong can be uncomfortable or even dangerous. It’s can be a major lifestyle change to do long EFs. Different people respond differently mentally. I’ve done up to 3 days. Sleep gets harder for me. Hunger obviously is an issue for most. I don’t do them often.
Unless you have some burning desire to fast for days, and your just trying to drop some weight, try IF. It can take a bit of time to acclimate, but soon becomes a normal routine. Eat healthy food in your windows. Hunger goes away as you acclimate and most find it leads to good weight loss without a lot of effort.
Start by skipping your first or last meal of the day. Be consistent. Eventually skip a second meal. Eat healthy, nutritious food. Once you’ve been doing that for a few weeks, see if you can go a full day without eating. Stay hydrated. Listen to your body. If you don’t make it as long as you wanted, it’s ok, it’s like exercising a muscle, it takes time to build up the strength to fast longer and longer.
Not stupid! We’re taught that regular meals are SO important (for most people, they’re not!) so it’s completely expected to be hesitant
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That said, you just stop eating and see how your body reacts. You’ll eventually hit a wall where you feel the need to stop the fast. As soon as your body says stop, you stop until you learn what your body is actually saying. Think about why and what was happening in your body. If you keep asking meaningful questions with each fast, you’ll find the answers that are important at that point in your journey
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Some starting out tips, though: