It’s not rocket science: Eat less and you’ll lose weight. The problem is, it’s hard to eat less all the time. What if there was a way to eat less sometimes, and still lose weight? Intermittent fasting is a strategy that focuses more on when you eat, and less on what you eat. The rules are simple—don’t eat on certain days or at certain times. There are different ways to do it: The 5:2 diet suggests eating normally 5 days out of the week, but limiting food intake to less than 500 calories 2 days a week. Alternate Day Fasting limits calories every other day. Time-restricted feeding recommends eating all your meals within a 6- to 8-hour window, and fasting for the remaining 16 to 18 hours a day.
For some people, fasting feels easier than cutting and counting calories, and studies show it’s just as effective in helping you lose weight. The major upside is that you may lose mostly fat, unlike normal diets (which restrict calories every day), where you end up losing a combination of fat and muscle. “Fasting for at least 12 hours a day puts you in a magic fat-burning zone, by changing the way your body burns carbohydrate and fat,” says Courtney Peterson, Ph.D., an assistant professor of nutrition sciences at University of Alabama at Birmingham. Celebrities and even athletes swear by this method, and it might be how your friend or coworker (finally! magically!) melted away those 20 pounds.
Fasting has shown numerous other health benefits, too, from slowing aging to lowering your risk for cancer, diabetes, and heart disease. The theory? The same way exercise stresses then strengthens your muscles, fasting stresses your cells, but then allows them to recover and become more resistant to disease. Admittedly, most of the research so far is with animals, but human studies show promise. Plus, compared to paleo, which claims to imitate how our ancestors ate, intermittent fasting actually comes closer. Your body is biologically hardwired to hang onto calories, because it anticipates periods of starvation.
But you also don’t want to become ravenous, distracted from your job, or hyper focused on food. Here’s how to practice intermittent fasting the safe and effective way—and keep your metabolism on its toes.
Breakfast Like a King
Peterson strongly recommends the early time-restricted method, eating all of your calories within 6 to 8 hours. Starting early maximizes the benefits by working with your body’s natural circadian rhythm, not against it. “We found that eating between 8 a.m. and 2 p.m., followed by an 18-hour daily fast, kept appetite levels more even, in comparison to the average American schedule,” says Peterson. “The first half of your day is when your digestion and blood sugar control are much more efficient, so if you’re going to skip a meal, it should be dinner, not breakfast.” Peterson also believes it may be possible to see some of the same benefits without fasting for such long periods. Start with a 9-hour eating window (8 a.m. to 5 p.m.), and work your way down from there, if necessary.
Leave Room for a Social Life
If you follow strict fasting hours during the week, it’s okay to relax on the weekends, and enjoy an evening meal out with friends and family. Fasting improves your metabolic flexibility (your body can be trained to switch more easily between burning carbs and fat), which means you don’t need to be disciplined every day. Researchers believe practicing intermittent fasting for 5 days a week may still result in some benefit—not all, but some. Of course, this doesn’t mean you can binge—the harmful effects of a high sugar, salt, or saturated fat diet won’t miraculously disappear! You still need to choose foods that provide the most nutrition for every mouthful.
Take a Sustainable Approach to Fasting
You can get the health benefits of intermittent fasting without taking it to the extreme. Going hours without eating will cause you to feel hungry at first, but after a few weeks, you’ll adapt to your new schedule. If you’re trying 5:2 or Alternate Day Fasting, avoid missing out on essential nutrients by eating healthy food whether you’re “fasting” or not. And on your low-calorie days, go for lean protein and veggies, which will help you feel fuller. If you’re doing the early time-restricted feeding, it’s important to plan your meals so that you eat enough calories in those 6 hours, or you’ll be starving and miss the point of challenging your metabolism.
If you still find these approaches too extreme, take aspects and apply them to your life in sustainable, achievable ways. Simply keeping dinner light by eating a salad or soup, and avoiding late-night snacking, has been shown to result in weight loss, too. You can get benefits without having to “go on a diet,” and you still get to eat dinner with your family—even if it means eating like a pauper.
Note: Fasting isn’t for everyone, particularly if you’re still growing (under 18 to 20 years old), pregnant, have a history of disordered eating, a chronic disease like diabetes, or are taking certain medications. Always talk to a health professional first.
This information is for educational purposes only and is not intended as a substitute for medical diagnosis or treatment. You should not use this information to diagnose or treat a health problem or condition. Always check with your doctor before changing your diet, altering your sleep habits, taking supplements, or starting a new fitness routine.
Tracy Morris
Tracy Morris is Fitbit’s Lead Nutritionist. With a master’s degree in nutrition and dietetics from South Africa, she’s also an Australian Accredited Practising Dietitian, and an international member of the Academy of Nutrition and Dietetics in the US. Over the past 20 years, Tracy's lived in five different countries, inspiring people around the globe to be healthy. She currently lives in sunny Sydney, Australia where she helps Fitbit fans around the globe live their best lives. When she’s not working, running after her three young kids, or practicing pilates, she can be found sipping pinot noir with her husband watching the sun set.
Totally agree with this! First thing that worked for me was to eat less. Noticed the transformation right away.
This is a nice summary of fasting. I’ve been fasting, and studying fasting, for 13 years (alternate day fasting). One thing I would quibble with is the idea that “The first half of your day is when your digestion and blood sugar control are much more efficient, so if you’re going to skip a meal, it should be dinner, not breakfast.” I suspect that varies between people, and most who follow the time-restricted method will find it easier to skip breakfast.
I just started intermittent fasting and I only eat from 11 am to 7 pm. I allow myself around 1400 calories per day. This is day 3 and I’m already getting used to skipping breakfast and my stomach already feels flatter. Are the hours I’m eating/fasting sufficient for losing weight. I currently weigh 226 and I’m 5’6″?
Debbie, it is the calories you consume each day which is the most important factor to helping you lose weight. If you are being strict on your 1400 per day and getting in adequate protein with some exercise each week then you are going to see results.
Great to see you are enjoying skipping breakfast 🙂
Agreed. I have been doing 5:2 since October. I find not eating until late afternoon, just 5 calories of hot broth, makes it much easier. Just staying hydrated and busy during the day and not eating until supper work for me. Once I eat, I stay hungry so I would struggle during the day. Everyone is different.
Have you lost weight doing the later 5:2 eating?
Hi Steve,
I am an exercise physiologist and have just written a book Called Start Late, Stay Light which details how skipping breakfast could help you live a happier, healthier and longer life.
I agree with you that most people actually find it easier to skip their morning meal as it fits into their social habits much easier.
Love to connect and hear about your research (info@startlatestaylight.com)
I hadn’t been using the Food aspect of my Fitbit but have this week started logging food as I want to be slimmer for my holiday in June. I am surprised as to how much it has actually inspired me to carry on and feel I can do this. I’ve always done a lot of walking especially with my and as the weather gets warmer again I hope to pick up my running again though I use the word ‘running’ loosely I have found the article on fasting very interesting and it could be something I may try later. I have usually done SW but for the first time in over 40 years I am calorie counting and love using the app
This essentially is the road to disordered eating. Surprised that Fitbit would publish something like this. Please don’t do this.
YES!! Thank you Mary. And surprised that if this is an RD where is the GOOD science, in other words: placebo controlled, double blinded, clinical trial, peer reviewed and repeated more than once with the same results. That is what it would take for me to be convinced.
No, Mary, really it isn’t. I’ve always skipped breakfast, for 40 years now, and it’s the way my body feels healthy. If you research that carefully, you’ll find many “authorities” (those who are not ravenous for breakfast) are beginning to understand that calling breakfast “the most important meal of the day” is not true for every body.
In addition, my truly skinny husband and I (not truly skinny, but not overweight, either) have both been doing the 5-2 diet for over three years now. We feel good, we eat well on all our fast days as well as our regular days, and my doctor just said yesterday, at my annual exam, that I’m amazingly healthy.
You may be uncomfortable with any sort of intermittent eating, but to suggest that the scientific research behind it is wrong, and that this will lead to disordered eating, is based on your lack of experience with how GOOD this makes many of us feel.
I agree. I read this article with large eyes and kept saying to myself “WHAT?!”. I eat when I’m hungry, keep an eye on calories, allow overage days and of course there are days I keep my intake lighter. This works for me without feeling deprived. I will NEVER skip dinner. How does anyone make it through the night or even fall asleep with a growling stomach?!
Agreed
That’s nonsense. Intermittent fasting has been around for some time and is gaining in popularity. I’ve been doing it for years and I’m an extremely healthy 55.
You have no idea what you are talking about. Fasting has been around before food was readily available..cures diabetes. I don’t mean to attack you but do a google search…
Totally disagree. It is something that our bodies are hardwired to cope with. Fasting is not starving, it is restricting and only giving it what it needs. Gluttony is something we have developed over the years.
At the age of 70, I went on the 5:2 diet and lost 50 pounds in 8 months all the while caring for my husband with Parkinson’s disease. It worked great for me and my blood pressure decreased and other numbers like cholesterol also decreases. I can now walk a lot more since taking off that weight. It has been a year now and I weigh regularly and if I have gained a few pounds, I go back on it and off comes the weight.
This is a great article. I’ve been doing intermittent fasting and have seen great results.
Only eating 500 calories a day seem low, wouldn’t that hurt u. I knw its only for two days.
Thanks for writing this. I’ve lost 80 pounds since July 2016 doing IF.
Congrats! That’s amazing…..your amazing
Not only is the fasting helping with health issues, it also does seem to make my body more adaptable. I stopped the fasting regimen for nearly a month in Italy where I feasted nightly and enjoyed snacks throughout the day.
Before fasting, that sort of eating would have led to a major weight gain but I only gained 3 pounds. But, that 3 pounds was apparently water. It was gone two days after flying home.
I’m going to stick with the fasting. My fasting blood sugar is down but I want to get it lower.
How would early meals- 16-18 hour fasting effect a person with type II diabeties.
Its complicated. Can someone explain this fasting method more clearly?
I started intermittent fasting two months ago when my weight loss virtually slowed to a snails pace. I fast from 6PM after dinner until 10AM most days. Of course there are times where our dinner plan run later than six so I will extend my fast accordingly the next morning. I always start with a healthy breakfast no matter what time I decide to break my fast. That is my favorite meal of the day. I may eat lunch within a few hours of my breakfast but I’m usually ready for it. Dinner on the table by 5 or 5:30 so that I can be done by 6PM. During the evening I will drink water or tea which keeps me full but generally I’m not hungry. My husband and I were terrible evening snackers, now we feel better, sleep better, and have consistently lost weight at a rate of 1-2lbs per week. We love it because we are not obsessed with the scale anymore.
DoesTracy Morris have a private practice in nutrition? Thank you.
For people who have found this to be successful, would you be willing to be specific about your regiment? This sounds like a viable option for me, but to be honest, I am confused. Can you do a time restricted method from 2pm to 8pm? That doesn’t seem to be a good idea, but it sounds like some people do this?
Thank you in advance for your info
I agree, eating breakfast is overrated although it is drummed into all of us as being so important. I usually don’t eat until midday so end up having just 2 meals a day. If I start eating earlier, I end up feeling hungrier and eating more and being more likely to eat unhealthy food.
I normally eat only from afternoon to evening, but I can’t go all morning without coffee. I wonder if this takes away from the fasting benefits.
started the 5:2 diet advocated by Michael Moseley a few years ago. Found I lost too much weight, (I was 65kg wanting to get to a healthier 62kg but went down to 58kg; have now got to a better weight) but now do it as a 6:1 and I feel that I get the same feeling of “putting my body in for a tune-up” each week without becoming gaunt.
Interesting article about selective fasting. Losing weight, however, is behavioral. During those fasting periods, acknowledge that you are hungery. Then you need to associate being hungery with being happy. One needs to enjoy being hungery as that will create weight loss. That’s the behavioral change that will make fasting work. It worked for me as I lost about 20 pounds 8 years ago and never gained it back.
This is poor advice. The best advice is eat less, cut down on sugars, fats and starches. Exercise more. It doesn’t, really matter when you eat. It is the amount and type of food you are eating. Just us good judgement and common sense.
I initiated a new regimen of low carbs in late April 2016 and increased the workouts. I was losing about 5 lbs a week for the first 40 – 45 lbs. Then the the plateaus started. In an effort to get things moving again I started intermittent fasting – no food from dinner until lunch the next day, with lunch being a protein drink. I’ll have dinner after work. Continued the early morning workouts, which helps as a hunger suppressant. Busy work mornings fly by and before I know it time has arrived for a protein drink. Also the quick lunch allowed for hour long lunch walks, another increase in the workouts. Lost 100 lbs in 10 months. Had hoped to lose the remaining 35 lbs and hit the goal weight by end of April 2017, but weight loss has slowed. Focus is to take it one day at a time. The journey has at time included days and weeks of discouragement, when there was no progress. One weekend after taking a new med recommended by a a doctor, for a painful ear that had fluid build up, I gained 18.5 lbs in 3 days. Side affect on the medication bottle stated possible swelling or rapid weight gain. Took me two weeks to take the 18.5 lbs back off, but I did it. Recently a bad cold affected my usual energy for hard workouts, as well as hunger, and I pick up 10 lbs very quickly. Working on taking that back off as the energy kicks back in, but over the long haul eventually it continues to go in the direction toward the goal weight. The intermittent fasting has definitely helped.
The intermittent fasting method is working very well for me too, having a late breakfast and early dinner. Great article.
Great article! Congratulation for this excellent information! I am in fasting diet since December. Skipping breakfast. I did not count calories, but a will do. Thanks for your support!
Jason Fung MD actually recommends IF for his diabetic patients. In Canada they work to save diabetics not give them a death sentence.
I think these comments are meant for those with a more than 20 pounds of weight loss in mind. I agree with Mary about this being the road to an eating disorder. As a recovering anorexic this would be dangerous for me.
I stood on the scale one day to see how easy it was to gain weight. I ate a pound of food. My weight went up a pound. Later in the day I ate a pound of food. My weight went up a pound again.
I guess I shouldn’t eat.
Why have a comments section, when the author of the article never responds to questions asked by readers? I notice this occurs with other articles as well. Fitbit, why post these articles, when they simply dead-end? With all the super-cool, hip people working for Fitbit … you can do better.
I’m 56 years old and have a heart condition. I’m not overweight, my heart condition is due to having Rheumatic fever at the age of 5. I’ve never yo yo dieted. I have and still do cleanse days, where I’m only drinking nutrient rich drinks and having no food for a whole day. I only do it one day a fortnight and the other days, I eat really healthy home cooked food. I work at a school canteen, therefore, I’m on the go for 5-6 hours without sitting. I walk and do some resistance exercise and enjoy time with my family. Living near the ocean, makes it easy to do lots of outdoor activeties.
I wish I could give it a try but I have a nutritionist that tells me to stop skipping breakfast so much she doesn’t want me skipping any meals
Great article for fasting beginners. I will definitely try time restricted feeding more habitually. I’ve done it before and thought it was helpful but I didn’t realize it was an actual method of fasting. I may also try the other methods to see which works best for me.
I find that my main meal is at lunch time and at supper I have a salad, small yogurt a glass of 1% milk and my 4 squares of dark chocolate. Perhaps that is to much for an 81year old lady but it works for me and of course I try not to have to much of my German Rye bread which I do not have with my main meal.
What do I do if I’m 13 and want to lose weight?
Please, please if you can, speak to your parents..or a family member. If its a medical condition, then they should help you seek a Dr out. But, please talk to someone.
Your body and brain are still growing and developing, so fasting isn’t good for you. Start by making sure you eat 3 solid meals each day with fruits and vegetables plus meat/protein. Then try to replace junk food like chips, candy, & soda with healthier foods like whole grains and water. Lastly, make sure you get 30 minutes of exercise every day, even if it’s just walking fast or doing Wii sports, or just your PE class at school.
If I fasting for 16hours will I still lose weight
It is VERY important for people to remember, as the last lines state, that this is not for everyone. We tend to have a very “one size fits all” approach to nutrition and diet and that is simply not the case. Everyone is so different and what may work wonders for one person will not work at all, and may even be detrimental, to the next.
For me, fasting was a disaster. It made me feel sick and light-headed. My sleeping was poor, and I felt just plain awful. I’m a person who needs to eat on a regular schedule. On the other hand, my coworker has found great successes with fasting.
Talk to a doctor and nutritionist and don’t feel pressured into doing things that do not feel right for you.
At the end of the day, the most important things are to exercise regularly and eat whole, healthy foods.
What about the whole “starvation mode” your body is supposed to go into when you restrict calories so harshly?? I also have a food logging app and whenever I don’t achieve my 1200 calories, it scolds me for not eating enough….AND I haven’t lost one pound in 3 weeks. I eat more healthy than anyone I know…
My only question is there a place where I can copy some of the 5/2 diet dishes I am ready I have try just about every one of them out here and instead of losing I gain , I do have a Tirol gland problem and I have try commercial diets as well famous Dr’s one green stuff and the hours at the gym I am ready to just let go I just want to be back to my healthy wait I am 5’3″ and tip at 165 lbs all in my mid section. so here goes nothing .
Thank you , you have open a new opportunity and I hope it works I don’t want to be 110 in 3 weeks but I would like to see me lose about 1.5 lb a week
so Thank you
i am inspired by this article and your post caught my attention as i am approx the same height and weight and also carry in mid section. as curious as to how this new way of life is going for you now that it is about 2 months since you posted.
thanks
leslie
I just want yo know, if during the fasting time..can you drink water. ..coffee…etc?
I have lost 45 pounds (236 to 191) in 5+ months. I eat more now than I ever did. 40 asparagus spears is equal to a slice of bread. (and I have done it) So is 30 strawberries or 3 bell peppers or 4 egg white eggs. I have no expertise but when I dropped from 1,600 calories a day to 1,000 calories a day for 9 days, I GAINED 3 pounds. Your body needs calories, especially if you are walking 6 miles a day. I am on a 45% carbs, 35% protein and 20% fat regimen now at 1,800 calories. Fasting is just out of the question for ME anyway.