There are many different ways one can fast.
You can skip dinner.
Participate in a seasonal four-time yearly fast.
Avoid food for a 24 hour period once a week.
Drink nothing but juice for an extended period of time.
But none of these fasting options sound all that desirable to me. However, 12 hour intermittent fasting is a different story. In my opinion, 12 hour intermittent fasting is the easiest and least painful way to go about fasting. If you are following an otherwise nutrient dense clean eating diet, it should actually be easy to do. As mentioned, I have been doing it more or less by accident for years.
Why Would You Want to Fast in the First Place?
For much of human history, sporadic access to food was likely the norm, especially for hunter-gatherers. Fasting to improve health dates back thousands of years, with Hippocrates and Plato among its earliest proponents. Although the idea of eating five or six small meals throughout the day has been popular among dieters, if you think about it, it is highly unlikely that people who lived 1000 years ago were eating three meals a day plus snacks.
Science is now starting to agree that keeping your stomach filled to the brim with food all day long might not be the healthiest thing to do after all. More recently, fasting diets are starting to gain popularity among mainstream doctors and scientists.
Modern Physicians are Incorporating Fasting Protocols Into their Diet Recommendations
Two doctors I highly respect, Terry Wahls, M.D. and David Perlmutter, M.D., both recommend fasting in their most recent books, The Wahls Protocol and Brain Maker (see photo above.)
***As a side note, Dr. Perlmutter is my former neurologist, he also wrote the foreword to my first book, The Gold Coast Cure. Dr. Wahls is a medical doctor who has reversed her symptoms of multiple sclerosis (MS) with nutrition and lifestyle modification.***
But Fasting Is Nothing New!
“There is nothing new, except what has been forgotten.” – Marie Antoinette
“The best of all medicines is resting and fasting.” – Benjamin Franklin
“Everyone has a physician inside him or her; we just have to help it in its work. The natural healing force within each one of us is the greatest force in getting well. Our food should be our medicine. Our medicine should be our food. But to eat when you are sick is to feed your sickness.” – Hippocrates
Of all the various ways to fast, 12 hour intermittent fasting seems to be the easiest and most pleasant way to go about the whole thing…
4 Health Benefits of 12 Hour Intermittent Fasting
There is good research to support a number of different health benefits of fasting. And you don’t need to avoid food for days on end to reap the benefits either! Here are some of the benefits of 12 Hour Intermittent Fasting.
- Improved Brain Health. Fasting has been shown to support mitochondrial health and anything that supports mitochondrial health also improves brain health. According to research published in Dr. Wahls book, there is even some evidence that intermittent fasting may reverse progressive brain disorders.
- Enhanced Detoxification. Your body is constantly trying to detoxify itself 24 hours a day. The body uses a great deal of energy to detoxify, but it also uses a great deal of energy to digest food. When your body is not busy digesting food, it can focus its energy on eliminating toxins and healing. Giving your body time to focus solely on cellular repair through the process of 12-hour intermittent fasting can be incredibly beneficial for optimizing detoxification.
- Reduced Inflammation. Fasting “turns on” the NRF2 gene pathway, which not only produces a dramatic increase in antioxidant protection and enhanced detoxification, but also decreases inflammation.
- Weight Loss / Weight Management. In general it takes between 6 to 8 hours for the body to burn through its glycogen supply. When glycogen is depleted the body will then turn to the energy stored in fat cells. Eating throughout the day makes it much harder for the body to burn fat. Extending the time between eating with 12 hour intermittent fasting will force your body to tap into stored fat reserves.
How to Incorporate 12 Hour Intermittent Fasting Into Your Day
If you want to try incorporating a 12 hour intermittent fast into your day, you’ll need to leave at least 12 hours between your evening meal and your morning meal. In other words, if you typically eat dinner at 7 pm then you will want to wait until at least 7 am before having anything else to eat.
If you have our book, you know we believe that it is never a good idea to eat if you are not hungry. My husband is never hungry for breakfast so he skips it all together. As for me, I find I typically can go about 14 hours between dinner and breakfast. Because of my husband’s work schedule, we typically don’t eat dinner until around 8 pm and I find I am not hungry for breakfast until at least 10:30–sometimes as late as 11!
I should point out though that if you are new to clean eating, you may find it very difficult to go for long periods of time between meals. Before I changed my diet, I distinctly remember how I not only always needed an after dinner snack, but I would wake up in the morning ravenous. I think you really need to be eating a nutrient-dense diet and have stable blood sugar before you can start going for long stretches without eating and still feel comfortable.
And speaking of feeling comfortable, I am not at all hungry during the dinner-breakfast “fasting” window either. I don’t think it’s a good idea to ever eat when you are not hungry, but I also think it is a bad idea to let yourself be miserable and hungry for hours on end too. Having said that, I do think if you are eating a nutrient dense diet and a solid and healthy dinner, you should find it rather easy to go 12 hours without eating. You could potentially be doing your body a big favor too!
Have You Experimented with 12 Hour Intermittent Fasting?
If so, please be sure to leave a comment and let me know how it has worked for you!
I have been doing intermittent fasting for a few days and find a 12 hr fast to be relatively easy, but the idea of going longer is daunting to me. What I am reading is that 16 to 24 hours is much better, even if done only once a week or even less often as the body reaches a “fasting state” after 12 hrs which accelerates the benefits. I am trying to find the pattern that is right for me.
Hi Michael, I don’t think the science is totally clear-cut just yet, but yes, I think that as long as you are not uncomfortable that going longer than 12 hours could potentially be more helpful. HOWEVER, if you feel at all uncomfortable going longer then 12 hours then I would say it could actually backfire because feeling uncomfortable (and the stress of being hungry) could actually raise cortisol levels, which would definitely NOT be helpful. So I think you are doing it right by seeing what feels comfortable. Listen to your body, that’s always what I suggest. Hope this helps?
In my experience, the results of fasting can really be astounding. Since intermittent fasting isn’t a diet, rather a pattern of eating or a way to schedule your meals so that your body gets the maximum benefit out of each one, it’s easier for people to follow. And when followed properly, intermittent fasting along with portion control (I wrote about it here: https://totalshape.com/diet/portion-control/) can be a great weight loss strategy for almost anyone.
I totally agree Michael! Thanks so much for sharing your input and the link 😉
can you use your sleep time as part of your fasting. I think 8am to 8pm eat. would this do the same thing.
yes!!! that’s the GREAT thing about it Lynda! There is no way I could fast from 8 in the morning until 8 pm, however I naturally just don’t get hungry before 8 am when I eat dinner at 8 pm, so I use sleep as part of the “fast” and then I just wait to eat breakfast until I get hungry. Today that wasn’t until 11:00.
Hello, I think I’ve been kinda doing this somewhat accidentally as well. I usually eat dinner between 6/7pm. I sleep in segments so I’ll sleep from 10:30-2:30 get work, etc then It will vary what I go back to sleep but am always back up at 2pm usually eating by 3pm. So if I go from 7pm as last meal to 3pm the next day that’s 20
Hours. The only thing is I will have a bowl of fruit and some nuts around 5am and then sometimes another snack because I thought it was bad to
Go that long without eating. So I guess it’s okay ..?? What if you have blood sugar issues? I was prediabetic but reversed it with diet but I still need to be careful.
Hi Laurie,
My husband is a surgeon and we have discussed this issue a lot. We believe as long as you listen to your body that it is ok to go for extended periods of time without eating. I would NOT recommend going without eating if you are feeling hungry or lightheaded however. This is all about tuning in to your body. The thing is, if you have blood sugar issues then your body will give you warning signs. There is actually research in the medical literature that short duration fasts may be a safe, tolerable, dietary intervention in patients with type 2 diabetes ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5394735/ ) But again, listening to your body is key. I definitely do NOT recommend fasting if you feel hungry the whole time. Instead, I would just concentrate on trying to eat only when you are hungry. I hope this makes sense?
Hi, the 5am snack kicks your body out of the fasted state, only water is allowed to benefit from a fast , not even a bite of food, or your body will produce insulin and stop burning fat.
Thank you so much for weighing in Naim!
During fasted state, one should drink water as much as possible to wash out toxins viz. Fat in the form of urine and exhalation, can drink black coffee without sweeteners, green or black tea to boost up metabolism and antioxidants in your body. One must break fast with foods that spark least insulin in the blood.
Your comment is awaiting moderation.
Hi, the 5am snack kicks your body out of the fasted state, only water is allowed to benefit from a fast , not even a bite of food, or your body will produce insulin and stop burning fat.
I have also been doing intermittent fasting without realizing. People have always given me grief when I tell them I am not hungry until 1pm. I have dinner around 6pm and sometimes a little snack afterwards (nothing later than 8pm). I wake up and have a coffee which keeps me going steady until around 1pm for my lunch. Breakfast has always made me feel a bit nauseous, unless it’s on a weekend but even then the earliest I would eat would be 10am. it’s great to know I have been doing my body good, especially without even realizing!
Hi Karissa! Thank you so much for sharing this. I am the same way (although I do get hungry a bit sooner than 1:00) —but I NEVER eat if I am not hungry. It’s just something I have never done long before I even knew it was healthy. I get sick and tired and sluggish if I eat when I am not hungry, that goes back to grade school. When I was growing up my dad always reinforced it was fine to just listen to my body and eat only when I was hungry (my mom never liked that advice he gave me lol but I still for some reason listened to him—he certainly was NOT a nutritionist. He was always very lean and healthy though! At 91 years old he STILL is.) Anyway, I am a big believer in listening to your body.
Due to my work schedule I eat my last meal before 9pm and don’t eat again until after 9am or longer. I am 60 years old and have been doing this quite awhile. I’ve lost weight in the past. I stayed around 190 – 195. Well I guess due to age It’s not working as good but keeps me around 205 in the spring – summer and 210 in fall – winter in Kansas City. It’s hard getting back to 195. I look better and feel better. I don’t want to starve myself to death 🙁 I have very good eating habits and drink plenty of water. Any suggestions?
Hi Terence, Oh I hear you! I am almost 42 years old now and although my weight is staying the same (so far, anyway!) one thing is for sure, there is NO WAY I can eat like I did 20 years ago (this was before I started eating clean). I think it just gets harder to maintain your weight as you get older. Having said that, the #1 biggest diet mistake people make is not eating anywhere near the amount of fruits and vegetables they should ( https://cleancuisine.com/the-1-biggest-diet-mistake-people-make/ ) —and this has a HUGE impact on your weight. If you do nothing else, make it a point to eat a fruit and vegetable with every meal. Don’t think so much about all of the “bad” foods you shouldn’t eat, but rather focus on the super good foods (the fruits and vegetables!) that will make a big difference in your overall health and weight. Also! Do you do any resistance training? Just adding 20 minutes 2 times a week of a full body strength workout along with 20 minutes of interval training 3 times a week is a workout formula that will definitely help make weight loss easier.
Please keep me posted on how it all goes! Hope this helps?
During fasted state, one should drink water as much as possible to wash out toxins viz. fat in the form of urine, sweat and exhalation, can drink black coffee without sweeteners, green or black tea to boost up metabolism and antioxidants in your body. One must break fast with foods that spark least insulin levels in the blood
The link you provide to support your article has nothing whatsoever to do with a 12 hour fast, it is “consuming 25% of energy needs on the fast day and ad libitum food intake on the following day.” Although there is data on the kind of fasting you describe (it is called “Time Restricted Feeding,”), TRF is generally within a 6-8 hour window. There is limited data on the benefits of TRF windows as long as 12 hours. You should redirect your readers to Pubmed.com and have them search for TRF, because it is deceptive as it stands.
Thank you for taking the time to comment John. Do you have the link to any research for TRF? I actually haven’t heard of that? I first heard about Intermittent Fasting (the way I describe it) from my neurologist and have since read about it in Dr. Wahls book and also online. But I am always open to reading more and would love to fully understand the difference between TRF and IF. Thank you again!
I’m in my first week of 12/12 intermittent fasting. It’s been a super busy spring break week and I’ve had the energy to keep up with all 3 kids all week. I’m hoping the next benefit will be some weight loss!
Hi Kristina! Oh SO good to know!! Thank you for the update—please be sure to keep me posted on how it all goes. Keeping up with 3 kids is no easy feat by the way—so congrats on that alone =)
I am on the ketogenic diet and have found 12 hours IF suits my schedule perfectly. I am not a breakfast eater, haven’t been since the late 1980’s and have found I have massive amounts of energy which I used to increase my workouts in the morning. Twelve hours is a perfect amount of time to fast between meals.
Thank you so much for sharing Kimberly! And I agree, I think 12 hours is just about right—it’s definitely doable if part of the time you are asleep 😉
Hi I am a college student. Is intermittent fasting good for me? I want to lose weight
I’ve been doing keto for a week now with 15 or 16 hrs of fasting. Doing fantastic! ut’s handling body problems I’ve had all my life.
Hi Lucille, I am so happy you are reaping so many benefits. Although we don’t follow a keto diet ourselves, I have heard many people say they feel better and I am so glad you are one of them! Even if you don’t end up sticking with keto long term (not sure if it is safe to do that?!) I would say you can absolutely do the intermittent fasting forever. I certainly plan to! Thank you for sharing your story. Wishing you all the best!
It’s my first time doing this 12 hours intermittent fasting, and my body starting to adapt. I don’t have problems with it its just that I feel some headache. But it’s fine, its manageable.
Hi Erik, Thanks so much for sharing your experience. If you are having headaches though you might want to shorten the hours —-maybe start with an 8 or 9 hour fast and slowly work up to 12 hours. Once your body adjusts you shouldn’t experience any negative side effects. I hope this helps? Please keep me posted on how things go!
I, too, have done this by accident. When I started Weight Watchers I realized that I was consuming a lot of calories late in the evening. All on “treats”. I would have a glass of wine after the kids were in bed – and what is better with wine than a bit of cheese – and you may as well have some crackers – and olives…. I instituted a no calories after 8pm rule and I never get around to breakfast before 9am. I am thinner and healthier for it.
Wow! Thanks so much for sharing Robin. I am so glad to hear it is working for you too!
I started 12-hour fasting 4 months back and do it every day. The only allowance is that I drink a glass of tea without sugar or milk in the morning during this fast period. I take a 60000 IU Vit-D tablet once a month. My Blood pressure which was 150/90 most of the time is now 122/77 most of the time.
Such great news about your blood pressure!! Thank you for sharing.
My first meal is at 5:30 am, my last meal is at 5:30pm, thats it until morning and it works for me, I eat 5 or 6 small meals, ……c
Am I allowed to have a cup of coffee in the morning? Is this just about not eating for 12 hours?
Hi Misty! That’s a great question. But yes, you are allowed to have coffee, however it is super important to not add any sugar. If you need something in it, a little coconut “cream” should be ok (I say “should” because there of course is not research to back this up, but I still a think a little coconut cream in your coffee is not the end of the world.)
Hi I am thinking of starting intermittent fasting By eating at 7am breakfast because that is normally when I finish exercise and skipping Lunch and then eating dinner Than waiting again until 7am next day and do it again. In your opinion does this make sense?Right now I stop eating at 8pm and eat again at 7am. But I have not notice any difference. Let me know your opinion
Hi Luis, Yes, this plan definitely makes sense if I am understanding it correctly. So, you are saying you want to do your “fast” in the middle of the day from 7 am till 7pm, is that right? Did you say you have been doing that already though and not noticing a difference?
Yes I started this program and I am also exercising with weight in the am so I start fast after I exercise around 7 am and eat breakfast and skipped lunch than eat dinner at 7pm. Not noticing much difference so I was also looking at doing maybe 16/8 not eating for 16 hours and eight hour eating window. What do you think? or is 12 hours good enough? I am looking to lose 15 pounds of fat.Thanks
Hi Luis, How long have you been doing the intermittent fasting? I think the 12 hours should be enough HOWEVER I would say that if 12 hours pass and you are still not super hungry, then you could absolutely push the fasting window to 14 or 16 hours. You don’t want to be uncomfortable during the fast, but you also should be hungry by the time 12 hours roll by if that makes sense? Also, be sure to look at the rest of your diet too! This blog post I did on the #1 biggest diet mistake people make might also be helpful.
Hi Ivy
I’ve just been diagnosed with diabetes and started weight watchers. I want to manage the diabetes with weight control. So I am trying a few different things, a tablespoon of apple cider vinegar every morning at 8 a.m. and because of my job my evening meal schedule changes but I do wait 12 hours before breakfast. My question is can I take the apple cider vinegar and a chew-able multi vitamin before the 12 hours.
Thanks for all this information
Ann
Hi Ann, I applaud you for attempting to control your diabetes with diet (I have been controlling my symptoms of MS for over 20 years with diet, exercise and nutrition supplements) As for the apple cider vinegar and multi-vitamin, both are GREAT to add to your diet! Neither one will disrupt the “fast”, however, you might want to consider taking the apple cider BEFORE your meals for the most benefit. You might also want to take your multi-vitamin with food since I am assuming (if it is a standard mutlti-vitamin) that some of the vitamins will be fat-soluble, such as vitamins A, D, E, and K. The fat soluble vitamins are all best absorbed with food. I hope this helps! And please keep me posted on how things go. Wishing you the best of luck!!
Thanks for the advice. I will make the changes and keep you posted
You are welcome Ann! And yes, please do keep me posted…
I began using the 12-12 method almost 2 months ago out of pure trial not knowing of it being an actual weight loss program. I had been feeling very lethargic and experiencing blood pressure spikes not knowing or accepting the fact I was borderline obese. I am ‘5 8″ teetering around 225 lbs which doesn’t seem like much for most people. I used to be an avid marathon runner typically weighing about 140 to 150 lbs at most so this extra baggage was causing great stress on my knees and back. I decided I needed to do something drastic to shed these unwanted pounds even If it meant changing my eating habits. I currently weigh 200 lbs and feel much more energetic not mention my blood pressure as dropped and the inflammation in my knees is gradually subsiding. I had been contemplating knee surgery but now I am putting it off as I slowly lose the weight and inch toward my ideal body weight.
Hi Louie, thank you so much for sharing your story! And WOW! I am so very happy for your success. I can only imagine how much better you must feel! The best thing about it is that I really do feel it is doable for the long-run too. Wishing you the best of luck and thank you again for sharing your great results!
I’m a bit confused. I always thought that not eating forced your body into “starvation” mode and made it store fat in a bid to aid survival. I know a lot of people that used to eat once per day ( dinner- probably overeating) and would be obese. When they followed nutritional counselling to eat throughout the day, they began to lose weight. Is there a balance? Perhaps too much fasting can have the opposite of the desired effect? I’d like your thoughts.
Hi Tammy, I absolutely understand why you are confused but here’s the thing, if you listen to your body and only eat when you are hungry then you will have a much easier time with weight management. Many people (including me and my husband) are not super hungry first thing in the morning but if we were to follow the conventional advice, which is to always eat breakfast, we wouldn’t necessarily be doing our body’s as much good as you might think. I am not a fan of long fasts because I agree, I do think the stress of not eating for days on end could push your body into “starvation mode”, but a short 12 hour fast is a totally different thing—ESPECIALLY if you are not naturally getting hungry during that window of time. And the more you optimize your nutrition during the time you eat, the longer your body will be able to comfortably go without food. If you are eating say donuts and coke for breakfast your body will lack nutrients and will be hungry soon after. If you ate the exact same number of calories but from a nutrient-dense smoothie with maca, acai, flaxseeds, etc. you would feel satisfied longer even though you had the same number of calories. And as long as you are not hungry during the 12 hour window, then your body is not in “starvation mode”. Keep in mind, hunger increases the stress hormone cortisol and that can start a cascade of metabolic issues, but if you are comfortable and not hungry, your body is not in stress and there is absolutely no reason to force yourself to eat just because it is “breakfast time”. I hope this makes sense?
hI,
I WAS THINKING OF TRYING THE 12 HOUR FAST PLAN BUT HAVE A QUESTION – CAN i STILL DRINK BLACK COFFEE? i HAVE ALWAYS DRANK MY COFFEE BLACK AND ADORE MY morning COFFEE SO i AM NOT SURE i CAN GIVE THAT UP. i USUALLY EAT DINNER BETWEEN 6PM-8PM ( WE HAVE WEIRD SCHEDULES) AND NOT EATING BREAKFAST UNTIL 8AM IS NORMAL FOR ME – GIVING UP MIDNIGHT STACKS WOULD BE THE CHALLENGE. hOWEVER, NOT DRINKING COFFEE UNTIL 8AM IS NOT GOING TO GO WELL FOR ME.
Hi Amanda, I totally understand your concern because I too would NOT do well without coffee in am. The good news is as long as it’s black you can still drink it on the “fast” =)
My monday – Friday fast time is 6:15-6:15. does it matter if i eat later on the weekends? does the fast “work” better if you are consistent with the times of day you eat?
Hi Beverly, that’s a great question! I haven’t thought about that before and although I don’t know the answer for certain, my best guess is that it doesn’t matter as much if you are consistent from day to day with the time, but rather just make sure the window is still 12 hours. Hope this helps?
I have been doing it little over a month now.learned it from my wife,and I usually go to 14-16hours. I feel great,hopefully I can keep it up for longer period
thanks
Been doing it for 19 days with great results. I am going for the 16 hour window now combined with cold morning showers for 5 minutes. I will keep you posted.
Hi George! SO good to hear! Yes, please keep me posted on the 16 hour window and the cold shower (we have a sauna in our house that I bought from Costco and at least once a week I do the sauna followed by as cold a shower as I can make it. You feel AMAZING after (but not so amazing while doing it lol) Anyway, please do keep me posted!
A million times thank you for this post Ivy! I’ve been wrestling with trying to make myself stick to 20:4 and 23:1 (OMAD) fasting because I was told it was best. to say that it has been a pain, is putting it insanely lightly! I am often told that 12:12 isn’t as effective. I’m going to try and switch to 12:12, I just hope my results are as impactful (a little nervous about that part). What do you eat during your eating window?
Hi Leslie! Oh gosh, I can only imagine the pain of trying to do a 20:4 or 23:1 schedule! That sounds just awful. I truly do feel you will get great results with this 12:12 schedule, assuming of course you eat clean. As for what I eat, it’s an anti-inflammatory, plant-rich (but NOT vegan) whole food diet. We explain it extensively in our Clean Cuisine nutrition book and in less detail in the upcoming Clean Cuisine Cookbook, but you can also check out the food pyramid and the basics here on this page: https://cleancuisine.com/start-here/ (just scroll down about halfway through!) I hope this helps?
And, please be sure to keep me posted on how things go with the 12:12 schedule…
Wishing you the best of luck!!
Hello, I Love this article. A FRIEND Suggested doing this 12hr diet and I have been doing it for the last few days after the Christmas indulge. I do find I am quite hungry but I’m getting by. Feel better already. I am vegan. I was wondering for how long I should do it for? A week? All the timd? Would love your advice, thank you
Hi David! I’m so glad to hear you like the article –thank you for the positive feedback! I’m also thrilled to hear you are starting to feel better. Ideally you should do it forever! It really does get easy though, within a week or so I think you will find your body adjusting to it and you won’t feel hungry during the “fast”. BUT, it is not optimal for your health if you are legitimately hungry (because that in and of itself will increase cortisol levels and be counterproductive to everything you are trying to accomplish) so what I would suggest if you are feeling hungry and fighting through the hunger is to just start with a 10 hour fast and wait until your body adjusts to that and then a few days later progress to an 11 hour fast and then a 12 hour fast. I hope that makes sense? Please keep me posted and let me know how it all goes!
I really like your website and your comment section. i was quite impressed with your information and the links to references. For me a 12 hour fast is easy but longer is hard. also does anyone have an opinion on eating too many nuts? I probably eat 2 servings of almonds, 2 servings of walnuts, and a serving of macadamia nuts every day. I don’t have a weight problem. I noticed that Steven Gundry, M.D. in “The plant paradox” limited nuts but i haven’t researched whether or not that is necessary if you are not worried about weight control. I also enjoy the wealth of information about the shorter fasts (less than 14 hours).
Thanks so much for your article. I a prediabetic and trying to fast for fourteen hours a day. I can’t do a lot of “smaller” meals during the day because it tends to keep my blood sugar high all the time so I’m trying to eat three meals a day with no snacks. I have been drinking water with a slice of lemon and a couple drops of stevia in it and I’m wondering if that is allowed during the fast time. I wasn’t sure if it would raise insulin levels or not.
Thank you for A very interesting read. Like many others who have commented, I have been on an overnight fast for at least twelve hours for many years without actually realising it. It is, however, nice to label it and learn about it’s positive effects. Although now semi retired, shift work in earlier life was the one thing that made the fasting regime very difficult, especially night shift. I have just been listening to a radio phone in, with a doctor who was discussing this very issue. It appears the incidents of type two diabetes, high cholesterol and depression are much higher in night workers. This, in my mind, reinforces how important it is to allow the body to self detox overnight during the fasting period.