Fast-5 is the weight loss / weight maintenance way of eating I’ve used since 1997. I described the method in The Fast-5 Diet and the Fast-5 Lifestyle, published in 2005. It’s very simple. Every day, you eat within a window of five consecutive hours. You can get the English version of the book from Amazon in paperback, on your Kindle or you can download the free PDF file.
My new book, AC: The Power of Appetite Correction, which has additional tools for weight loss, is also available in paperback, on Kindle, and as audio versions on Amazon and Audible.
The Fast-5 book and/or its summary and Frequently Asked Questions (FAQ) page are available in these languages:
| English | Summary FAQ (Frequently Asked Questions) |
| French/Francais | Résumé QFD – Questions Fréquemment Demandées Livre |
| Dutch / Nederlands | Samenvatting Veelgestelde vragen Boek |
| German / Deutsch | Zusammenfassung Häufig gestellte Fragen |
| Portuguese / Português | Resumo Perguntas Freqüentes |
| Spanish / Español | Resumen Preguntas Hechas Frecuentemente |
| Swedish / Svenska | Sammanfattning Vanliga frågor |
41 comments
I have lost 10 pounds in just 2 months. It works! Thank you, Dr. Herring! I read your books and will keep them for life. Your videos and books are authentically helpful.
I am a medical scientist, I have tried all kinds of diet, and this one turned out to be the most effective, simple and enjoyable. You deserve a medal for helping so many people.
Thank you for commenting! I’m happy it’s working for you and wish you all the best on your weight loss / weight maintenance lifestyle journey!
Hello Mr. Herring,
I suffer from headache and bad halitosis during the fasting period. I work very close with people and this is a problem for me.
Do you have a suggestion what to do to make it better?
Greetings from Germany,
Sabine
Having a headache during the adjustment phase isn’t common, but it isn’t rare, either. Typically, regular headache medicines such as ibuprofen will help. As you adjust, they are very likely to go away completely. How to handle the halitosis problem depends on what kind of halitosis you’re having. If people are smelling ketones on your breath, descriptions vary from “chemical” to “fruity” or maybe a bit like fingernail polish (acetone). This too, typically goes away as your body adapts and starts slurping up the ketones you’re making as fuel. Thorough and consistent dental care (2x daily brushing and 1 x daily flossing, including the brushing the tongue or scraping it with floss) may help. If the halitosis is persistent or smells foul, there may be something going on besides the smell of ketones from fasting that’s worth a look from your doctor or dentist.
I just wanted to say thank you. I’m 3 weeks in and am now seeing that many of the wise words you share work. 1.) setting a window to eat while socializing and 2.) don’t expect weight loss for 3 weeks.
My window is 2-7 pm, it worked very well when we had a holiday weekend last week, we had company and it was great I could eat dinner with them. Although I made breakfast for them, I did not eat.
Also, just lost my first pound at the 3 week mark.
Thanks for adding your comment! As you point out, a social “diet” is very important for health and a long, happy lifestyle, so having a compatible window helps make the lifestyle easier and more fun. Congrats on the 1-pound loss! Please keep in mind your loss may be steady (about the same every week) or bumpy (two pounds in one week, none the next), but as long as it’s going down on average, you’ll get to your goal. Best wishes to you for your success!
Does the fast 5 dieting hours have to be between 5pm and 10pm?? Can it work if it’s 7am to 12pm? If not, please explain why.
Thanks for asking! No, the window doesn’t have to be 5pm-10pm — that is used as an example. While the books says the window can be adapted to your schedule, I didn’t emphasize this enough as this is the most frequently asked question (FAQ) about Fast-5. There’s more on this and other FAQs here: https://www.bertherring.com/ac/fast-5/faq/ The optimal window depends on your work, personal, family and social schedules. Some people have been successful with a “sliding window” that they adjust according to the needs of the day. I encourage people to try the fixed window first, then try tweaks like that once they’ve seen a few weeks of steady progress and know how Fast-5 feels when it’s working.
Hi. I started about 10 days ago and it is going fine. I am of course hungry slot, but it is getting betting. I am also doing a lot of cross-fit during my fasting periods, 3 times a week. It is very hard after training, especially coming home at the weekend to a family enjoying breakfast. Question is can I have rest days? Not days when I become an eating monster but days where I still watch what I eat and drink but not when I eat and drink. I am soon going on holiday with my family and it will be hard to continue without being anti-social. Best Mark
I hope this gets to you in time for your trip, as I’ve had some family time away, too. Regarding rest days — yes! A rest day (or off day) is fine. (Some people call these cheat days, but I avoid the term because it’s not cheating when it’s part of your overall plan.) It’s like putting the car in neutral. You probably won’t make progress, but you won’t lose your adaptation unless you go off for several days in a row. You can expect to be clock-hungry when you go back to your fasting schedule, but if you can busy yourself with other things, the clock hunger typically passes without much discomfort or distraction. When you are with others on a non-fasting schedule, you can do a few things to help yourself: 1) delay your break-fast as long as possible and ; 2) when it’s comfortable, have a beverage instead of a meal, such as choosing to have coffee only when others are having breakfast; 3) avoid snacks between meals; eat early in the evening and avoid late-night intake when doing so does not takes the fun out of social times!
I’ve read a lot about eating during the five hour window but what about drinks? Is it just water? Are cocktails allowed occasionally while trying to lose or should that be avoided while trying to lose weight? What can I drink during the nineteen hour window? I’m new to this just trying to get the most out of it.
Anything calorie-free is okay for most to drink during the fasting period. That includes flavored water such as coffee, tea and unsweetened seltzer drinks (such as LaCroix). A few people have reported that their progress stalled until they dropped artificial sweeteners, but others have had great progress while continuing to consume them. There’s no way to know which type you are until you try. During the eating window, drinks of any kind are fine, with the usual moderation of alcohol and keeping sugary drinks to a minimum just so you don’t undermine your progress by taking in loads of calories.
I have your book from when it first came out. I am a good friend of your mother in law Mary M. We worked and lived in Oakland Md many years ago. I always admired her for keeping her weight off using the Fast 5 diet. I am 78 and Iam trying it. Should I be taking any vitamins or supplements. Oh yes i was at your wedding at the goat ranch. Hope you and your family are well. I am a snow bird. Go back to Va. in. June. Thank you.
Thanks for writing, Karen! It’s great to hear from you. As far as vitamins and supplements go, none are needed if you choose a healthy diet with variety and generous portions of plants. If you’re not sure, there’s no harm in taking a multivitamin or mineral supplement so your body gets what it needs. If you’re not deficient in vitamins or minerals, adding extra doesn’t do any good and in some cases, it can be harmful. One of the vitamins most likely to be deficient is D, especially if you don’t drink milk or get much sun exposure. If it hasn’t been checked already, your doctor can check your vitamin D level to see if you need a supplement. Best wishes for your success!
would you have any recommendations for children to do fasting
especially 11 to 15 years
There’s a bit on this in my book (AC: The Power of Appetite Correction). For kids, I suggest preparing one meal per day and allowing the kid to have all-day access to vegetables and fruit that they must choose to get or fix themselves. Reducing eating frequency is a big challenge when schools are providing or encouraging snacks. Schools often encourage kids to eat every few hours because they think the kids’ brains need tons of glucose. Parents may need to get a pediatrician involved to convince the school staff that childhood obesity is the problem they should be concerned about, not insufficient glucose for learning and for a healthy child, going without food for a few hours is not harmful.
I’ve been intermittent fasting the last 4 years and feel great as long as I don’t eat. I’m eating between 4 and 7(8) pm and suffer from hyper insulin after eating even if I do not eat carbs(or low carbs). The doctors I visit are against fasting and say that cortisol is taking over in my fasting period,which is not good for the adrenal glands which affects my thyroid (which is already slow working(but no medicines) ). I love IF and could do this for the rest of my life but I’m worried and do not know what to do if IF is not making me feel better concerning my hyper insulin and thyroid ? Thanks for your advice….
If you can back up a bit and say how you know you’re suffering from hyperinsulinism, that’d be very helpful. If your insulin is running high, your glucose would be very low. How high is your insulin? How low is your glucose? If you haven’t measured either and are relying on symptoms, you can check your glucose level yourself with the kind of glucometer that diabetics use or ask a doctor or testing lab for an insulin test when you’re feeling the symptoms.
Hello,
I am a 26 years old woman and I was wondering if there could been any link with fasting 5 hours and having more facial hairs. Indeed, I practice intermittent fasting since at least 3 years, but the 16-8. I tried the 19-5 schedule, which was OK as well. However, I found studies stating that intermittent fasting drastically increases testosterone production, which can cause more hairs, acne, seborrhea, hair loss, and menstrual cycle irregularity. I have been having more acne and facial hairs recently, and their are darker too. Not a too big deal at the moment but I would rather not increase those traits. Have you any studies on the topic you could share? What do you think about this?
There have been many reports of beneficial skin changes from Fast-5ers over the years, including a decrease or resolution of acne. Many websites blame intermittent fasting for evils because it’s free and effective and might reduce their sales of supplements, diet services or whatever they’re selling. Others just cook up things to get attention and traffic, so it’s hard to know what’s legit. You can trust your body, though, and yourself. Intermittent fasting works differently in different people, so the best way to know what’s going on in your case is to look at your body. You can ask your doctor to check your testosterone level after several weeks on a consistent intermittent fasting schedule. If it’s not high, then testosterone isn’t the issue. If it’s high, go back to a conventional eating schedule for a couple of months and then check it again. Compare the two results—if your testosterone is still high, then you may have an endocrine problem that isn’t related to fasting. Best wishes for your long-term health!
Why not OMAD?
Why OMAD (one meal a [per] day)? A 5-hour window gives the same results with greater flexibility for social times with family and friends, which are a very important part of a healthy diet. A 5-hour window also gives a person the opportunity to eat something a little later, so there’s not a temptation to overeat during the single meal of an OMAD schedule.
Will having a coffee with 2 tablespoons of avocado oil and 14 grams of unsalted butter break my fast?
Yes. Anything with calorie content breaks a fast. The important question is “Does it matter?” and only you can determine that by trying it out. What works for you may not work for others, and what works for others may not work for you.
In your 5 hour window should you do a snack and one meal or two actual meals ?
Personally, I do one meal then snack as I please for the rest of the window. Many Fast-5ers have been successful with two small meals, one at the beginning of the window, and one at the end.
Any advice for those of us who work a night shift? I typically work from 10 pm to 8 am and go to bed around 9 or 10 am. Should I stick to the regular feeding times or eat while at work?
As long as you can get a consistent window sometime, it doesn’t matter when it is. Many Fast-5ers on conventional work schedules have been successful with morning and mid-day windows. The main reason for having the window late in the day is for social compatibility with friends and family, so setting the window when you’re most likely to be having social time (such as meals at work with others) is important.
How many hours should there be between your last meal and sleeping? Wake up at 2am. Go to bed around 6-7pm
It depends on your personal preferences. Some people feel uncomfortable going to bed on a full stomach and prefer to have at least 2 hours between their window closing and bedtime. For people on a typical schedule, 3-8pm works well in this case. If you have social contact with friends/family, it’s often nice to be able to eat with them, so that can push your window earlier or later, too. If you’re going to bed at six pm, a comfortable window might be 11am-4pm, if that’s compatible with work and family.
Just wondering why the window is 5 to 10? I prefer a eating window of 1:30 pm to 5:30 or 6:30. I have been doing this for two weeks and do notice a appetite correction, with food cravings going away. Thank you.
The window can be whatever works for your schedule. 5pm-10pm was intended as an example that accommodates evening social time. I indicate in the book that it can be moved, but did not emphasize that flexibility enough to make that clear. This is the most frequently asked question about Fast-5. Many people have been successful with earlier windows, such as 1-6 pm and 3-8 pm, as well as morning windows.
More about the window and other frequently asked questions is available here:
https://www.bertherring.com/ac/fast-5/faq/
Best wishes for your success,
Bert
I’ve been doing this for the past 10 days. I have no craving and no nagging hunger. I feel more peaceful, sleep extremely well, and aches and pains have disappeared. My 5 hour feeding time is between 5 and 10 pm. Food tastes wonderful and I desire vegetables and clean nutritious food. Processed food now tastes awful. I eat whatever I want until full, and fullness actually comes pretty quickly. I have no desire to snack on junk all night and I feel free from the constant hunger, cravings and the eating all day long, never being satisfied. I have lost 5 pounds and that’s a plus. I think I can do this the rest of my life!
Hello,
i’ve started the fast 5 for two weeks now, feels good. But a question. I read that bringing your body is ‘ ketose’ it is not that good for you, because the body makes it’s own ‘sugar’ called methylgloxal, and this is very bad for your body. Can anyone tell me more about this?
On this diet as your stored glycogen is depleted your body will begin producing ketones which becomes “sugar” for the brain. This is a sign that you are burning stored fat. It is an acidic chemical so you must drink water during the fasting period as it could be irritating to the kidneys. When you eat during your 5 hour window the ketones will go away.
Does anyone has experience with the combination of sports during the day and the Fast-5 lifestyle?
Most people find Fast-5 completely compatible with sports during the fasting period. A long distance swimmer I know found his performance better on a fasting schedule after doing his “study of one” comparing his times when swimming fasted vs. conventional eating. Most people I’ve heard from who exercise on Fast-5 prefer to do it during the fasting window when they’re gut is not busy digesting food.
I got the same question … If I run at 8am eat between 11am and 4pm and dance/ play tennis/squash between 7 and 10 pm…. 🙁 this sounds a bit cruel. But he might be right and I just think it is cruel because I grow up like I did (at least eat 3 times a day AND if your hungry- EAT) …
So I will just give it a try.. is it too hart. I´ll eat in a 6 (or even 7) h window at first…. I will start tomorrow.. I´d be interested in your opinion and results…
I’ve been fasting 19 hours for 3 weeks now. I run 5-8 K on some mornings and last week I walked in the Alpes 4 hours a day. I eat between 5-10pm and it feels great. No problems whatsoever! I lost 6 lbs already!
I don’t do “sports” but I do some heavy duty gardening and I feel less fatigue and actually have more stamina.