14 intermittent fasting rules for success
For an effective method of losing weight and improving your health, intermittent fasting (IF) is refreshingly light on rules (ironic, given the title of this article).
And, because we know that change happens more easily when people control their own path, we’re not here to start laying down the intermittent fasting law.
That said, we also know that change happens more easily when you know how to really work a tool to its fullest advantage. So what we are going to do is give you some principles to do just that. Not intermittent fasting rules, per se, but intermittent fasting best practices.
These are the top actions to maximize the impact of IF and allow you to get the absolute most from your efforts!
- Intermittent fasting is an effective way to lose weight and improve your health.
- IF works better if it’s teamed up with high-quality nutrition. Your food choices matter.
- Exercise can boost your intermittent fasting results.
- Decreasing your stress can improve your intermittent fasting outcomes.
- Intermittent fasting doesn’t need to take over your life to help you reach your goals!
14 intermittent fasting rules
Without further ado, here are our top 14 best practices for crushing your goals using intermittent fasting.
1. Don’t eat during your fasting window
Yet it’s worth thinking about because it’s not that difficult to break your fast without realizing it, especially with drinks and especially when you’re new to IF.
Don’t worry! We’ve got you covered. Here’s everything you need to know to keep you from falling into this hole in two handy guides:
Give these guides the once over, and you’ll be set to keep your fast intact with no errant calories creeping in!
If this kind of information helps you be a better faster, why not take our SIMPLE quiz and get hooked up with our app? We have all kinds of useful tools and insights to support you as you practice fasting, and it’ll all fit in your pocket!
2. Be consistent with your eating window
Routine can help a lot with intermittent fasting.
Say you follow a 16/8 fasting schedule, for instance, and start your eating window at 11 AM every day. Over time, you’ll get pretty used to that. It’ll become part of your regular routine, and you’ll build your morning around it.
Once you’ve done something lots of times, it becomes a habit, and habits make things easier.
This doesn’t mean you can’t ever change your fasting / eating times, of course. There’ll be days you need to. But on the whole, sticking to the same routine will make your fasting life much easier to execute.
3. Stay hydrated!
OK, even though we said no fasting rules, this actually may be one. Not because we’re the fasting police and you have to DO WHAT WE SAY, GOSHDARNIT, but because, as humans, we need water. (The body makes its own rules. What can ya do? [shrugs])
When you fast, your water intake drops because you get some of your water from food. That means you gotta drink more than normal to stay hydrated.
So while it may mean more trips to the toilet, staying hydrated also makes your body function better, may help you lose weight more effectively, and can curb some of intermittent fasting’s tricky side effects like hunger, cravings, and headaches.
4. Make sure you’re eating enough food
Not eating enough is one of the most common reasons why intermittent fasting can feel like it’s not working for you.
By “enough,” we mean:
- enough to function well, feel good, and think clearly
- enough that your hunger isn’t off the charts, your cravings aren’t screaming bloody murder, and your thoughts aren’t dominated by food
- enough that your metabolism doesn’t slow down, and you don’t end up burning muscle for energy
You can eat enough to satisfy your needs and still lose weight.
In fact, eating enough will help you lose weight because it’s sustainable, whereas undereating tends to lead to overeating, binging, and the stop-start-stop of yo-yo dieting.
That’s what makes eating enough one of our rules (that’s not really a rule because you’re a grown-up who can make their own decisions) of intermittent fasting. Whether you’re trying to lose weight or not, eating enough food is crucial.
5. What you eat matters
There are no specific rules for what to eat during intermittent fasting, but what you eat does matter. It’s one of the biggest determinants of what you’ll ultimately achieve.
The 411 here:
- eat lots of veggies, fruits, lean protein, whole grains, calcium-rich foods, and healthy fats
- eat less refined carbs, ultra-processed foods, and unhealthy fats
Whether you want better health, a leaner physique, improved blood sugar management, increased energy, or anything else in the health and wellness realm … your food choices gotta align with your goals.
6. Going keto could improve your results
It’s not guaranteed, but doing intermittent fasting with keto could boost your results by getting your body more reliably and/or more quickly into ketosis.
Some people don’t reach ketosis with intermittent fasting alone, so keto can bump things along nicely.
7. Eating low-carb could improve your results
In a similar vein, reducing the amount of carbs you eat (not necessarily going keto; there are various forms of low-carb diet plan you can try) could also be a good pairing with intermittent fasting.
Following a low-carb diet means both storing less excess glucose as fat and more fat used for fuel, which can lead to weight loss and shrink your waist circumference.
8. Don’t go overboard with milk in your coffee
Let’s apply a bit of SIMPLE thinking to make an easy-to-remember rule of fasting around milk in coffee. You can have milk in your coffee when fasting … but when you do, follow this quick One-Two rule:
One coffee with two tablespoons of milk max per fast.
Go at it like that, and your fast will stay intact, giving you all the hard-won benefits of your food-free hours.
9. Be sparing with sweeteners
While artificial sweeteners aren’t something to consume a lot of, our science team is confident you’re in no danger from a couple zero-cal sodas a day, and neither is your fast.
A zero-calorie can of fizz here and there is not gonna hurt. Just don’t make it the backbone of your fasting hydration strategy (that’s water’s job).
10. Replenish your electrolytes
If you’re new to fasting, you can end up running a little short on electrolytes like potassium, sodium, calcium, and magnesium due to your body losing water as you deplete your glycogen stores during your fast.
You might also need to supplement if you’re fasting longer than 16 hours. Having a shorter eating window means you’re likely eating less food, which can mean you’re not getting enough through your diet.
If you notice headaches or dizziness in either scenario, try adding some electrolytes to your water.
11. Get active
Exercise may be the ultimate intermittent fasting ride or die. It’s like a booster switch for all the benefits of intermittent fasting.
It can help you lose weight, improve your blood pressure, regulate your blood sugar, and reduce your risk of chronic diseases. It’s one of the actions that helps make sure that intermittent fasting does not slow your metabolism.
To crank up the power of your IF routine, throw some regular movement into the mix. If you have questions about how to do this, we got answers. Learn how to combine intermittent fasting and working out here.
12. Destress your fasting (and your life)
This one may seem at first a little … well … stressful.
As soon as someone says, “You must not stress, or it’ll kill your results!!” what’s most likely your first response? Stress, right?
Yes, stress can get in the way of losing weight, and it’s not ideal from an optimal health perspective. That said, stress IS part of life, and we need it (a completely stress-free life wouldn’t be healthy either; stress helps us grow).
The objective here is to make your stress manageable — to get it into the growth zone so it can help you rather than harm you. So, think about
- What’s stressing you out at the moment?
- What stressors can you alleviate and how?
- How do you currently manage stress?
- Is it working for you? If not, what can you do differently?
and see what actions you can take.
13. Slow and steady
When approaching any change, go slow and steady. What do we know about slow and steady? It wins the race.
Losing weight and improving your health isn’t a race, but sometimes we can get caught up trying to go as fast as possible because we want the results NOW.
That’s understandable. Having patience is tough when you really care about the goal you’re working towards.
But going slow works way better in the long run. Although a 16-hour fast might feel doable when you’re high on motivation, it’ll quickly become tough as nails to execute when your motivation naturally dips (this is normal) and life crowds in. A 12-hour fast, by contrast, is easier to keep in place even with those obstacles.
Same with dietary changes. Performing a wholescale overhaul on your entire diet will quickly get pretty dang hard. But just changing your breakfast? That’s doable.
Start small and build up over time. Get your 12-hour fast locked in, then extend it to 13, 14, 15, and 16 hours with practice. Get your breakfast looking sharp and nutritionally on point, then move on to lunch, snacks, and dinner (one at a time).
14. Keep living a full life
Yes, it takes focused effort to reach a goal, so by all means, knuckle down. But there’s absolutely no reason why IF should take over your life.
Stay flexible. If you need to take a day off — to rest, to celebrate a birthday with late-night tacos, or just because the day ran away from you — no sweat. Just hop back into the swing of things the next day.
Learn only as much as you need to feel confident in what you’re doing. You don’t need to know the molecular structure of protein or the precise mechanisms of ketosis. (We can hear the sighs of relief from here.)
Being a die-hard IF expert doesn’t increase results. The only thing that increases results is consistently taking the right actions over long periods of time — and melding those actions into your everyday routine.
We can help you with that. Take our SIMPLE quiz, and our app will assist you in making intermittent fasting a regular part of your day-to-day life.
Why are these intermittent fasting rules so important?
These intermittent fasting rules, aka best practices, are super important because they make it more likely you’ll achieve your goals.
Alone, intermittent fasting can only achieve so much. It’s like, say, the trumpet section in an orchestra. You need other instruments to make the full symphony happen.
Are the rules the same for every intermittent fasting schedule?
These guidelines work great with every intermittent fasting schedule.
Whether you’re following a time-restricted fasting method, like 12/12 or 16/8, or a fasting plan like alternate day fasting or 5:2, you’ll need to eat enough, eat quality foods, keep your fast unbroken, drink plenty of water, and so on.
You may not need to pay attention to your electrolyte balance with 12–16 hour fasts, but otherwise, these “rules” of fasting are good to go across the board.
How does intermittent fasting work?
There are some specific rules to how intermittent fasting works, of course. But only a couple:
- You follow a cyclical pattern of eating, then fasting, then eating, then fasting, ad infinitum (until you choose to stop).
- The specific pattern will be determined by the intermittent fasting plan you choose. (We’ll lay these out in the next section).
What happens in your body during the fasting period is responsible for some of IF’s impact. In short, the lack of food causes your body to go into ketosis and start burning fat for fuel.
And what happens during the eating window is also responsible for some of IF’s impact. In essence, because the eating window is a specific length of time, it naturally curbs your calorie intake and helps you create a caloric deficit (where you eat less than you burn).
These two things — ketosis and reduced calories — lead to weight loss , and fasting is also known to lead to reduced inflammation, better-regulated blood sugar, decreased blood pressure, and better overall metabolic health.[3,4,5,6]
The different types of intermittent fasting
Intermittent fasting comes in various flavors.
These are the ones we recommend at SIMPLE:
- Time-restricted eating methods, like
- 16/8 intermittent fasting
- 18/6 intermittent fasting (for advanced fasters)
- 20/4 intermittent fasting (for advanced fasters)
They’re pretty safe, they are fairly well researched, and they can lead to some impressive results.
These are the ones that we only recommend with the OK from your doctor and, ideally, the supervision of a dietitian:
These are also well researched and show good results, but they require long fasts with little nutrition. So check with your doctor first and, ideally, work with a dietitian to come up with a meal plan that meets your nutritional needs.
And these are the ones we never recommend:
They’re pretty hard to sustain, they don’t look after your body’s nutritional needs, and they’re not necessary to get results. You can hit your goals with the other methods just as well and more safely.
Intermittent fasting benefits
If you’re still wondering, “Is fasting good for you?” then let’s get you up to speed. As long-time fans of intermittent fasting, we’re always excited to talk through the benefits.
Here’s a quick list:
- weight loss 
- reduced belly fat 
- immune system support 
- muscle mass maintenance 
- improved insulin sensitivity  and lower risk of diabetes
- reduced oxidative stress 
- better blood pressure 
- lower cholesterol levels 
- improved heart health 
- lower risk of metabolic syndrome 
- better brain health 
Dig into the full story and science behind each one of these wicked intermittent fasting benefits here if you’re curious!
5 tips for success when intermittent fasting
What are the rules for intermittent fasting, if not simply tips for success? We have a few more of those for you, casting our net a little wider afield into the arena of behavior change. Here are five to get you started.
- Tap into your motivation
When the going gets tough, the tough know where they’re going.
The first couple weeks of IF can be challenging: learning to manage your hunger, dealing with cravings, getting used to a new routine where you can’t be so free and easy with food, etc.
Having a strong grasp on why you’re doing IF — what you want to achieve and how it will change your life — will help you hang in there.
- Implement a clean slate policy
Cut yourself some slack.
Sure, these practices are important, but focusing too hard on doing everything “perfectly” only increases stress. It’s OK to make mistakes and have messy days where things don’t go to plan.
Give it your best shot. You’ll probably surprise yourself with how quickly you pick things up!
When things go wrong, prevent it from tripping your Quit Switch with this 2-step process:
- Learn from it. What can you do differently next time?
- Let it go. Water off a duck’s back.
This takes practice, but being able to wipe the slate clean as and when needed will help you every single week (sometimes every day).
- Remember, protein is your friend
One trick that can help you through that initial hungry patch: eat more protein.
Make sure to get at least a portion of protein with every meal, and if you snack, shoot for protein-based snacks too. (This is actually a good rule of thumb in general.)
- Get some support
It can feel hard to share your goals and plans with others, but having someone you trust to root for you, help you troubleshoot, pick you up when you fall down, etc., is so valuable.
Find your cheerleaders, trusted advisors, and emotional support animals, and bring them on board. (May we also suggest our FB group as a good place to find some community.)
- Develop your meal planning skills
Having a solid intermittent fasting meal plan in place can make a lot of difference, whether you’re just starting out or you’re a seasoned IF professional.
Planning your meals ahead of time takes many of the in-the-moment decisions out of the equation, meaning your food choices are not so susceptible to hunger, cravings, and those “can’t be bothered” after-work vibes.
SIMPLE’s expert opinion and final thoughts
When you’re just getting started with intermittent fasting, focus on that and that alone. When you feel you’ve got the hang of it, that’s the time to start tightening and tweaking these rules of fasting to maximize your results.
Use the above list as a checklist to find areas you can improve. Maybe take each one in turn and see — what can you squeeze from it?
And when it comes to building your support team, we’re right here for all your fasting needs, whether it’s reminders to keep you on track, a food diary to help you get clear on what you’re eating, or insights into the change process. Try our SIMPLE quiz, and make us your emotional support app!
Frequently asked questions about intermittent fasting rules
What is the first rule of intermittent fasting?
The first rule of intermittent fasting is … don’t break your fast!
Without a strong, intact, periodic fast, you won’t reap the benefits of intermittent fasting.
What happens if you skip a day of intermittent fasting?
Nothing dramatic! If you skip a day of intermittent fasting, no worries. Simply get back to it the day after, and it’ll be as if it never happened at all.
(Try not to make a habit of it, though. You need consistency to create meaningful change.)
What not to do in intermittent fasting?
What not to do in intermittent fasting broadly comes down to these four basics:
- don’t eat during your fasting window
- don’t fast during your eating window
- don’t get dehydrated
- don’t forget to eat lots of foods rich in a variety of nutrients
There are lots of other don’t-dos, but we prefer to deal with do-dos [snicker]. The article above will give you plenty of ideas.
What should I avoid during intermittent fasting?
Here’s a very quick list of four things you should (ideally) avoid during intermittent fasting:
- any calorie-containing food or drink during your fasts
- foods that are ultra-processed, refined, and high in unhealthy fats
Those last two we often think will help us nail the changes we’re trying to make, but they generally hinder rather than help.
Which meal is best to skip for intermittent fasting?
The meal that is best to skip for intermittent fasting is:
the one you can most easily live without.
Although studies suggest that you’re better off skipping breakfast  rather than dinner, this decision is all about what makes sense for you!
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