Intermittent fasting to lose weight | explained by Simple
Picture it: you’re at your happy weight. No calorie trackers. No diets. No extra-demanding workout plans.
Sounds too good to be true, right?
Maybe not—with the help of intermittent fasting.
Before you dive down the rabbit hole of googling “weight loss intermittent fasting,” we can explain.
Intermittent fasting for weight loss involves focusing on when you eat rather than what you eat. Instead of calorie restrictions or strict meal plans, intermittent fasting is a food routine made up of timed windows of eating and fasting.
Fasting to lose weight can be an effective way to shed pounds and boost your overall metabolic health, but like any routine, it isn’t a good fit for everyone.
So if you’re wondering how to lose weight by intermittent fasting and if it’s right for you, your body, and your goals, our experts have put together a simple guide to explain the process.
- Intermittent fasting involves a repeated pattern of eating and fasting that focuses on when you eat rather than what you eat—and it can be a safe, effective way to lose weight.
- There are several ways intermittent fasting may help with weight loss, like priming your body to burn fat, preserving lean muscle mass, and reducing waist circumference.
- You can take several different approaches to fasting for weight loss, but what we know so far suggests a 5:2 diet and alternate day fasting may lead to more significant weight loss, at least in the short term.
- To gain muscle and lose fat in the process, you should eat nutrient-dense, health-promoting foods like fruits and veggies, whole grains, lean protein, and healthy fats during your eating window.
- Intermittent fasting isn’t for everyone, and it may not be a good fit for every weight loss journey, so if you’re unsure, consult your doctor or dietitian before trying it.
What is intermittent fasting?
Before we dig into using fasting to lose weight and what that diet may look like, here’s a quick recap of what intermittent fasting is and how it all works.
As far as eating habits go, intermittent fasting is a super simple three-step routine:
- You eat during a certain period.
- You take a complete break from eating for another defined period.
- Then you do it all again.
There are several different types of intermittent fasting plans, and your specific eat-fast-repeat routine can vary. Fasting and eating windows can differ, and some plans are daily, while others are based on alternate days or weekly schedules.
Although some versions of intermittent fasting can involve additional elements of calorie restriction or meal-planning recommendations, at its core, intermittent fasting is all about the timing of your food routine.
Intrigued? We’ll get into how it works and how it may help with weight loss, but first, it’s important to remember: everybody is unique, so intermittent fasting may have different impacts on different people, and it may not be right for you.
You should be particularly cautious about considering a fasting-based food routine if you:
- Are pregnant, breastfeeding, or trying to conceive;
- Have a history of disordered eating;
- Have diabetes or another chronic medical condition;
- Have poor or irregular digestion;
- Are under 18 or over 65 years old; or
- Are taking prescribed medication (for example, anti-hypertensives, diabetes medications, or any that need to be taken with food).
To see if intermittent fasting might help you reach/maintain your happy weight, take our SIMPLE quiz. We also always recommend consulting your doctor or dietitian before making any significant changes to how you eat, especially if you identify with any of the above considerations.
How does intermittent fasting work?
Intermittent fasting works by priming your body to burn fat instead of sugar as its source of fuel.
Imagine you just ate lunch.
(Pause for stomach grumbles and food fantasies.)
When you finish a meal, your body starts digesting and absorbing all the food you ate to use as helpful body stuff, like energy, fat, muscle, and brain power.
After a few hours, your body enters what’s called the post-absorptive state—basically an internal version of flopping on the couch after several intense rounds of snacking. It’s happy here, divvying up nutrients and shuttling them to where they need to go for the next 8–12 hours.
Then it enters a fasted state. And this is where the fat-burning magic starts to happen.
Since you probably wouldn’t normally go twelve hours without eating, intermittent fasting—timed breaks from eating done in a certain way—works as a trigger for this natural fat-burning phase. By priming your body to gobble up fat stores as swiftly as the seagull who swoops in to steal your French fries, fasting can improve your body’s overall functioning.
Can intermittent fasting help with weight loss?
Now for the big question: can you lose weight by intermittent fasting?
The short answer is yes.
There are a few “buts” to consider—and we’ll get to those—but existing research largely supports the idea that intermittent fasting could promote weight loss, at least in the short term (up to 12 months). Some research also suggests it can help you maintain your happy weight once you get there.
Now, about those “buts” …
There are three important caveats to keep in mind about intermittent fasting when it comes to weight loss.
The first is that some research suggests intermittent fasting may not necessarily be better for weight loss than calorie-restriction diets, and it may not lead to weight loss benefits without other lifestyle changes. But if you’re tired of counting calories, yo-yo dieting, and obsessively checking macros on restaurant menus, it’s still worth a try.
The second is that more inclusive research is needed before we can really say how effective intermittent fasting is for weight loss. Existing research focuses primarily on small sample sizes or specific populations, like people living with obesity. It fails to explore the effects of fasting specifically on trans men and women, nonbinary people, and individuals currently on hormone replacement therapy.
Finally, the third caveat is that your body is a beautiful, one-of-a-kind individual, and fasting may not work for—or be healthy for—you. So can you lose weight by intermittent fasting? We recommend speaking with your doctor first to find out if a fasting-based way of eating might work for you. Plus, our SIMPLE quiz is here to help you figure out if intermittent fasting is your key to unlocking your happy weight, too!
How much weight can you lose while fasting?
Brace yourselves for an answer that may cause as much frustration as when your favorite show got canceled: it depends.
We get it; whether you have a love or a hate relationship with numbers, it’s comforting to have at least some benchmark figures to keep in mind.
However, since everybody is unique, fasting weight loss can vary significantly and depends on lots of factors outside your fasting plan.
For example, your individual circumstances, like starting weight, medical conditions, lifestyle, age, and activity levels, can impact the weight you lose as much as the type of fasting approach you take and the food you eat during your eating windows.
It’s not all up in the air, though. When it comes to losing weight and what to expect, there is a good rule of thumb to keep in mind. While some people may experience more rapid weight loss, the healthiest—and most enduring—weight loss is gradual. Losing one or two pounds a week is safe, effective, and totally feasible.
How does intermittent fasting and weight loss work?
So how does intermittent fasting work for weight loss exactly?
There are several effects intermittent fasting can have that could lead to weight loss:
- Make your body a fat-burning machine. It’s important to understand the distinction between fat loss vs. weight loss, but intermittent fasting can help with both (though its results are still comparable with calorie restriction).
- Preserve lean muscle mass. Particularly when combined with resistance training, fasting can promote lean muscles and lower body fat percentages.
- Reduce waist circumference and belly fat. Research suggests intermittent fasting may be more effective than calorie restriction, specifically for waist circumference.
- Help control your appetite. Avoiding those late-night munchies can work wonders.
In addition to these direct connections to weight loss, intermittent fasting can also benefit your body in other ways, like reducing inflammation, decreasing cholesterol and blood glucose levels, and supporting heart health—all of which may individually or collectively contribute to weight loss.
What is the best intermittent fasting plan for weight loss?
All intermittent fasting plans may improve your metabolic health, but some research suggests some are more effective for weight loss than others. To help you figure out what approaches you can take, how to do intermittent fasting for weight loss, and what plans might be the best fit for your goals, our experts have outlined the most common methods. If you want to dive more into the basics first, check out our intermittent fasting for beginners guide.
With an intermittent fasting 16/8 plan, you alternate between 16 hours of fasting and an eight-hour eating window. As long as you stick to this schedule, what you eat and when you eat is up to you. Can’t live without your morning motivation of breakfast cereal? Skip dinner. Need to unwind at the end of the day over comfort food? Skip breakfast. Though FYI, for the best results, we don’t recommend living off fast food, pizza, and cake!
Though this plan may be a good place to start for fasting beginners since it’s basically an extension of the natural daily fast that happens when you sleep, its weight loss results may be more limited compared to other approaches. However, our users have had weight loss success both with this approach and with other less researched time-restricted eating approaches like 12/12 or 14/10.
The Warrior Diet is a stricter version of time-restricted eating (with 20 hours of fasting and a four-hour eating window), but so far, there isn’t much research about this fasting plan, specifically with respect to its weight loss capabilities. We also recommend speaking to your doctor/healthcare provider before doing a fast longer than 18 hours.
Fasting on different days
Following the 5:2 diet involves eating as you normally would for five days of the week and fasting (restricting your calorie intake to 500 or 600 calories) for the other two. Similarly, alternate day fasting involves alternating days of eating normally and days of fasting (eating 500 to 600 calories).
Both of these eating routines can be more difficult to manage around your daily life and require slightly more careful meal planning to ensure you’re getting all the nutrients you need during your fasting days. However, they do have one big plus: both plans have been linked to more significant weight loss when compared to other intermittent fasting methods. So if you’re focused on how to lose weight with intermittent fasting, these approaches might be a good match.
One of the more challenging types of intermittent fasting—the Eat Stop Eat method—means eating as you normally would for one day before fasting for 24 hours until the following day. While you get to eat your standard amount of food during your eating windows and technically get at least one meal every day, a 24-hour fast can be tricky to manage in terms of getting in all your nutrients.
While restricting calories for a full day at a time may be effective for weight loss since burning more calories than you consume is linked to losing weight, there’s no current evidence to suggest this type of calorie restriction is more effective than continual daily calorie restriction. Furthermore, we don’t recommend it, especially without medical supervision, since this level of restriction can more easily lead to nutrient deficiencies.
How to gain muscle and lose fat with intermittent fasting
Of course, losing weight isn’t just about shedding pounds, and it’s important to remember that a number on a scale doesn’t equate to or define your health.
Safe, effective, and lasting weight loss is about focusing on your unique body composition and ensuring you’re not just dropping water weight or losing muscle tone.
Think of your body like the superhero you are: you want to maximize power, not minimize pounds.
What does that mean in practice? When you’re choosing an approach to help you reach your happy weight, don’t just ask, “can you lose weight with intermittent fasting” or “how to burn fat,” but also, “how can you gain muscle and strength while losing fat.”
There is some evidence to suggest that pairing intermittent fasting with resistance training and moderate protein intake can improve the quality and strength of your muscles. On the other hand, some research questions if regular intermittent fasting, regardless of other lifestyle factors, might be counterproductive to muscle mass by encouraging the body to burn muscle as well as body fat.
While more research is needed to determine the best intermittent fasting methods for muscle gain and fat loss, many scientists agree that eating nutrient-dense foods and avoiding foods that are highly processed or high in sugar and sodium can boost your results and promote better overall body functioning. We’ll dig into some foods to consider for your menu in the next section.
Another lifestyle factor that can impact your fasting results is physical activity. Exercising in a fasted state may stimulate more fat burning; however, some studies also suggest it may not significantly affect muscle strength.
Regardless of your current physical activity or exercise levels, if you’re considering switching to a fasting-based eating routine, you want to be careful not to push your body too hard because your body won’t be used to exerting itself in a fasted state. So, if you do want to build physical activity into your routine, start small, be patient, and try out different types of activities. Even if your goal is to build muscle strength, there’s no need to panic-buy training equipment, either. Shout out to 2020 lockdowns and discovering that tons of household items—like all those spare wine bottles—can work perfectly for some light strength training …
What should I eat to get the best weight loss results when intermittent fasting
There’s no one-size-fits-all approach to what you eat and drink during your fasting plan. As with any food routine, you should use your health goals, nutritional needs, preferences, budget, and schedule to help plan what works for you.
That said, to maximize your weight loss with intermittent fasting, you want to focus on nutrient-dense, health-promoting foods that provide the stuff your body needs to be strong and feel its best, including vitamins and minerals.
These types of food include
- fruits and vegetables
- whole grains (like oats, quinoa, and brown rice)
- legumes (like chickpeas, beans, and lentils)
- lean protein (like tofu, fish, and poultry)
- dairy products or calcium-fortified plant-based alternatives (like yogurt, cheese, and fortified oat milk)
- healthy fats (like nuts, avocados, and eggs)
You should also limit foods that are
- ultra-processed (like fast food, cookies, and chips)
- foods high in refined sugar (like candy, cakes, and desserts)
- foods high in sodium (like cured meats, pizza, and fried food)
- foods high in saturated and trans fats (look for hydrogenated oil in the ingredients listed).
Similarly, when it comes to what you can drink while fasting, you should stick to things like water and plain, unsweetened tea and coffee during your fasting window. You should also limit fruit juice, alcohol, and sugar-sweetened soda altogether. Since science is still working out what impact diet drinks have on health, we recommend limiting the diet stuff to two cans per day, too.
Whatever health or weight loss goals you have, remember to cut yourself a little slack. We may not recommend nightly binges of ice cream and bottomless pizza, but food is never inherently “good” or “bad.” Some foods are just more nutrient-dense than others, and life is way too short to keep your hand out of the cookie jar 24/7, 365 days a year!
For more ideas and meal planning inspo, check out our guide on what to eat during intermittent fasting.
5 tips for success when intermittent fasting to lose weight
If your intermittent fasting weight loss journey feels like it’s filled with potholes, dead ends, and wrong turns, our experts have mapped out some ways to help you navigate it smoothly.
1. Pick a fasting schedule that works for you
To set yourself up for success, you want to pick an approach that can work around your schedule, daily routines, and other commitments. While intermittent fasting for weight loss may require some slight rerouting of habits, you never want it to be a roadblock to getting on with your life.
2. Start slow
Imagine being given the keys to a sports car and entered into a race when you haven’t even learned how to drive yet. Terrifying, right? The same is true for fasting for weight loss: you want to get the basics down first and make sure you’re comfortable with all the tools, signals, and gears before you ramp up.
3. Enlist some support
Sure, a solo road trip may get you to where you want to be, but isn’t it a lot easier—and more fun—to have someone along for the ride, helping you navigate and providing encouragement? Having a great support system in place can improve your chances of sticking to your plan and reaching your destination. Just watch out for those judgy types, you know the ones—nobody likes a backseat driver!
4. Stay hydrated
Some days it may feel like coffee is your fuel, but water is what your body really needs to remove waste, burn fat, regulate blood pressure, and do a whole lot of other valuable stuff that may help with weight loss. If you’re not a fan of plain water, try sprucing it up with fruits and spices like lemon, mint, or cinnamon. You can also drink plain, unsweetened green tea: it contains catechin, which may help to suppress appetite.
5. Be kind to yourself
Particularly when you’re just starting out, the ride to weight loss success can feel more like a tilt-o-whirl than a pleasant drive through the countryside. Bouts of hunger, hanger, irritability, headaches, fatigue, and sleep disturbances are only some of the unwelcome detours you may experience along the way, but practicing self-compassion and avoiding guilt or judgment will take you far in whatever path you choose.
Simple’s expert opinion and final thoughts
The team here at Simple all agree: the best eating routine for safe, effective, and lasting weight loss is the one that is right for your unique body—and one that you can stick to.
All intermittent fasting approaches can benefit your body and mind, but everyone responds to fasting differently, and fasting may not be a good fit for your weight loss journey. Especially if you’ve never fasted before, we recommend trying out a limited time-restricted approach before committing to a longer, more intense one.
To learn more about which intermittent fasting protocol might work best for you and get tips on when and how to get started, stay motivated, and reach/maintain your happy weight, take our SIMPLE quiz today.
Frequently asked questions about fasting to lose weight
Is fasting a good way to lose weight?
Intermittent fasting can be a good way both to lose weight safely and effectively and to maintain your happy weight. It’s not for everyone, though, and everybody responds to fasting differently, so you want to factor in your unique needs and speak with your doctor or dietitian to help find a plan that might work for you.
How many hours of fasting are good for weight loss?
While any intermittent fasting plan can be good for safe, lasting weight loss, how many hours of fasting are good for weight loss is still debatable. Some research suggests that following certain approaches (specifically the 5:2 diet and alternate day fasting) may lead to more significant weight loss. Bodies react to fasting differently, but generally speaking, your body needs to go without food for 12–16 hours to enter its fasted, fat-burning state.
Do you lose belly fat by fasting?
Although some studies suggest time-restricted eating can reduce belly fat and associated metabolic risk factors in certain conditions, existing research into if you lose belly fat by fasting is still limited to small populations.
Which fasting is best for rapid weight loss?
We never recommend fasting to lose weight quickly, as the safest and longest-lasting weight loss is gradual. However, with what we know so far, alternate day fasting and the 5:2 diet might lead to more significant weight loss than time-restricted eating or full-day-fasting plans.
How do you maximize fat loss when fasting?
- Drink black coffee or green tea during your fasting window.
- Break your fast with nutrient-dense meals (think whole grains, lean protein, fruits and veggies, and healthy fats).
- Stay active and focus on fat-burning physical activities like HIIT training and prolonged incline walking.