16/8, 18/6, 20/4, or OMAD: Which Fasting is Right for You?

One of the leading weight loss plans in our modern world today is intermittent fasting. Intermittent fasting, or IM, is a routine where you refrain from eating for a certain amount of time, and only allow yourself to eat during specific regulated hours.

This primarily helps to minimize the incidence of snacking, eating because you're bored or eating just to eat, which is one of the hardest challenges of weight loss. Food is, after all, delicious, and many foods contain substances that could even be considered mildly addictive. Restraining yourself from eating or "cheating" on your diet is extremely difficult.

There are a bunch of different schedules for intermittent fasting, which is why we were so unspecific right there. In fact, picking the right schedule that works for you is one of the most crucial decisions you'll make when embarking on a plan to fast. Let's discuss the most popular schedules, and how to choose the one that's right for you.

How Intermittent Fasting Works

If you've ever tried to start and stick to a diet plan, you know it can be really difficult. You almost always have to cut out some of your favorite foods, or even entire categories of foods, and you often replace them with foods you might not enjoy. Worse, you have to stick with it for years on end, if not the entire rest of your life.

So what if someone told you that you could eat whatever you wanted and could still lose weight? Obviously, you'd be skeptical but intrigued. Skeptical, because that's the kind of pitch that come with snake oil, those magic diet pills that often do more harm than good. Intrigued, because if it works, it would be great.

This is where intermittent fasting comes in. With intermittent fasting, you can practically eat whatever you want; you don't restrict what you eat, you restrict when you eat. This means you end up eating less, because you're not allowing yourself to eat outside of designated hours.

"Won't I just eat everything I was going to eat before during those hours instead?" Well, maybe. You could! Most people, though, find that they eat one meal and fill themselves up, and then they don't want to eat any more because they're full. You end up eating less because your desire to eat is diminished during those hours, and once you fall outside those hours, you don't allow yourself to eat.

This is also easier to keep up because, if you have a craving for one of your favorite foods, you can just eat it! You don't have to constantly yearn for something you can't have. You can just save it for a few hours from now when you're able to eat, and sate those cravings. 

Now, here's where science comes into play. In order to lose weight, you need to burn more calories than you consume. No matter what. There is no pill that can change this equation. There is no exercise plan that changes this math. It's as immutable as the laws of physics themselves. 

Intermittent fasting helps you to suppress the amount of food you're eating, that is, the calories you're taking in. There are also some studies that suggest fasting increases norepinephrine production, which is a hormone that stimulates your metabolism. After all, if your body needs energy while you're fasting, it needs to get it from somewhere, and that somewhere is burning your stored energy supplies; your body fat.

However, if you pack a ton of food into your stomach during the time you're allowed to eat, and you don't do anything to help burn more calories when you're fasting, you're not going to get much out of intermittent fasting. You still need to maintain that caloric deficit, no matter what.

Now, there are a bunch of different kinds of intermittent fasting schedules. These schedules dictate which hours you're able to eat and when you're supposed to fast. They're meant to be rigid to keep you on track, so you want to pick something that works best for you. No one schedule is inherently better than any other; it all depends on the person. So here are the most popular schedules you can choose from.

16/8 Fasting

Most fasting schedules are formatted as a pair of numbers. This is the off/on hours for eating, out of a given day. So the first schedule, the 16/8 schedule, is 16 hours of fasting each day and 8 hours where you're allowed to eat.

So to put this into perspective, let's say you're working a normal 9-5 job. That's 8 hours. That's also the time you're allowed to eat during the day. Any time before 9am, you can't eat. Any time after 5pm, you can't eat. 

You can, of course, adjust this to fit your schedule, so long as you keep the pattern regularly. If you know you need a hearty breakfast to make it through the work day, maybe you start at 7am to accommodate that breakfast. Of course, that means you have to stop eating by 3pm, which means you're probably skipping dinner. Conversely, if you want to make dinner with your family a regular occurrence, you can push the schedule back to 7pm as the cutoff point, but that means you can't start eating for the day until 11am.

As you can see, this offers one large challenge, which is the need to cut off either breakfast or dinner. You'll have to balance which of the two you want more. No cheating is allowed, and you can't adjust your schedule to fit each day, so you have to pick a schedule and stick with it.

18/6 Fasting

18/6 fasting is already more difficult than 16/8, and you can already see why. It's 18 hours of the day you're not allowed to eat, and only 6 hours of the day where you can eat. With only six hours of the day available to eat, your schedule becomes very strict.

Many people tend to center their fasts around dinner, because dinner is usually the most robust meal of the day. If you have dinner at 6pm, you want to give yourself some time to eat, so you base your schedule around it. With six available hours, you might say you give yourself until 8pm in case dinner is a little late. So you have from 2pm to 8pm to eat. Anything later than 8pm or earlier than 2pm is off limits. No breakfast and, usually, no lunch.

Most people trying this kind of fast end up eating a late lunch as soon as they're able, and snack a little between then and dinner, to ensure they have the calories to keep going. Of course, you have to watch out that you don't over-eat and over-compensate.

20/4 Fasting

If you looked at the 18/6 fasting schedule and thought it was difficult, be prepared to be astounded. Some people go for a 20/4 fasting schedule. That's right: only four hours of the day are open for eating. Again, typically this is centered around dinner, and it generally means just one meal per day. You might give yourself from 5pm to 9pm to eat, with dinner at the front of that period, and a little snacking near the end to make sure you pack in enough calories to survive a day.

This is an extremely difficult kind of fasting, and most people can't handle it. This is the kind of fasting that comes with a very strict, rigid routine. It's very much not something beginners can do, and even experienced intermittent fasting practitioners have a hard time keeping it up.

OMAD Fasting

This one doesn't even have numbers, but it does have the word MAD in it, so it can't be easy. In fact, many would say that someone trying this schedule would be quite mad themselves. 

OMAD stands for One Meal A Day, and it's exactly what it sounds like. You have one shot, one opportunity to eat each day, and you have to make it count. No time period where you can snack to top yourself off. No additional bits here and there. You get one meal, once every 24 hours, and that's it. 

For most people, this means you end up with a single meal of around 1,400-1,800 calories. That's a lot to eat in one meal! It might not seem like much, and it's not for a full day, but eating that much in a single meal can be quite difficult sometimes.


Of course, many people trying out OMAD take it too far in the other direction. Knowing they can only eat one meal, they eat a BIG meal, to try to make sure they have enough food to last them. They end up eating 3,000 calories or more, and then they wonder why they aren't losing weight. Remember, the average person burns around 2,500 calories per day without more than basic exercise, so eating more than that will destroy your ability to lose weight.

Other Schedules

There are a few other kinds of intermittent fasting schedules. We're only going to cover them in brief, because really, you can set any kind of schedule you want, so long as it's restricted.

5:2 ADF. This schedule is Alternate Day Fasting, and it means you spend five days a week eating normally, and two days a week – not back to back – eating under 500 calories in the day. Rather than spreading out your fasting throughout the week, you bundle it up into two days. 

10/2x2. This, and other similar plans, are intermittent fasting schedules that give you two different, narrow periods to eat during the day. Ten hours off, two hours on, ten hours off, two hours on, repeat. 

12/12. This is the easiest form of intermittent fasting; 12 hours on, 12 hours off. It's quite simple, and many people actually live like this without realizing it. As such, it's not much better than baseline.

Considerations for Intermittent Fasting

When you're deciding what kind of intermittent fasting schedule you want to use, you have to keep a few considerations in mind.

Your life schedule. We mentioned above the idea of dinner with your family. That can be an important part of your day, so you want to pick a schedule that allows you to have that meal consistently. You have to wrap the rest of your meals into a schedule that allows for this dinner.

Keeping your schedule in mind is crucial, but it can be difficult if, say, you work a retail job with no consistent hours. It can be hard to eat a full meal at work when you only have a 15 minute break, if that. In these cases, a broader schedule might be better, with self-imposed restrictions on top of it.

Existing health issues. If you have health issues, you definitely want to talk to your doctor before starting intermittent fasting. Some issues can be exacerbated by not getting enough food throughout the day. On the other hand, some issues – like high blood pressure, prediabetes, and obesity – can be improved through intermittent fasting.

Blood sugar issues are some of the most critical to keep in mind when you're trying intermittent fasting. Fasting can lead to a drop in blood sugar, and that can lead to a range of side effects, from headaches to passing out.

Gender. There's some evidence that suggests that intermittent fasting is not as effective for women as it is for men. It can lead to issue with your menstrual cycle and fertility, among other things. Make sure you keep an eye on your body and measure your results if you try it.

Your willpower. At the end of the day, the schedule you choose depends on your ability to stick with it. You can pick OMAD all you like, but if you cheat every other day, it's not a good diet that works for you. Make sure to pick a schedule that you can keep up.

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