8-Hour Diet: Fast 16 Hours to Lose

The 8 Hour Diet is a popular weight loss plan from David Zinczenko the author of the best-selling book Eat This Not That.

8 hour eating window

With this diet, David promises readers that they can lose 20-60 pounds or more and still eat whatever they want.

The key to the 8 Hour Diet is only consuming calories within an eight-hour window each day.

Zinczenko himself lost 7 pounds by eating according to this method.

His concept isn’t entirely new as there have been several diets over the years that promote intermittent fasting as a way to lose weight. Here’s how his version works.

8 Hour Diet Basics

This diet works on the theory that the human body is designed for periods of eating and then periods of fasting.

This involves consuming calories over an 8-hour period and then fasting for a 16-hour period each day. During the 16-hour period, the human body should be focused on repair and rest, rather than continually digesting food.

8 Hour Food Window

All of a dieter’s daily calories must be consumed only during his/her predetermined 8-hour eating window.

For example, if your calorie window is from 9 am to 5 pm, you must eat during that time period only.

The window can be adjusted depending on a person’s schedule and can be different during different days of the week. Dieters should eat this way at least 3 days a week at the beginning of the diet and gradually increase towards the ultimate goal of 7 days a week.

Eat Whatever You Want

8 hour diet explainedThere are no forbidden foods on The Eight Hour Diet, but Zinczenko does advise that this diet is not an excuse to overeat. Portion size must still be considered.

The only exception to this rule is sugary beverages since the 8 Hour Diet discourages drinking calories.

Delay Breakfast

Dieters should delay eating breakfast until the beginning of their food window. For example, If you can’t start eating until 10 am, Zinczenko recommends starting the day with a cup of tea, water, or coffee and doing some light exercise before any calories are consumed. (similar to 6 Weeks to OMG Diet)

Eat as Often as You Want

Snacks can be eaten as often as a dieter wants as long as all eating is within the 8 Hour Diet window.

Portion size should be considered when choosing snacks.

Supercharge the Diet

The 8 Hour Diet shows dieters how choosing 8 healthier power foods instead of processed and refined foods can dramatically increase the effectiveness of the diet and the dieter’s overall good health. The book gives suggestions on how to easily incorporate these foods into the diet.

Sample Meal Plan

Upon Rising

Water, coffee, or tea

Breakfast (10 am)

Oatmeal with blueberries and maple syrup
Coffee, tea, or water


1 granola bar


2 slices of pizza
1 8oz bag of potato chips
1 apple


1 fudge brownie

Dinner (5:30 pm)

Grilled Salmon Steak
Baked sweet potato w/butter
1 cup of broccoli
½ cup ice cream

Only 8 Minutes of Exercise

To be successful on the 8 Hour Diet just eight minutes of exercise is required to turbocharge the fat burning process.

Exercise suggestions for the most effective calorie burn are included in the book. 

The Cost of the Diet

The 8 Hour Diet: Watch the Pounds Disappear Without Watching What You Eat retails for $26.

Buy this book from Amazon.

Zinczenko Talks About His Diet

Why The 8 Hour Diet Works

  • It all comes down to calorie restriction. If you can find a way to keep the calories low enough to result in weight loss, you will be successful. By only having 8-hours to consume your food, you might be able to trick the body into taking in fewer calories.
  • This diet reminds me of a couple of years ago when Oprah talked about cutting off your eating at 6 pm as a way to lose weight. This became a popular diet trend for a while because it helped to prevent late night overeating and excess calorie consumption.
  • Intermittent fasting has shown health benefits.
  • Another benefit is that you don’t have to deprive yourself. Many of us have been through so many diets that we feel overwhelmingly deprived. This is bad for our long term success. We need to learn how to feel comfortable making choices that aren’t so healthy, but in exercising excellent moderation and portion control. 

The bottom line is: The body knows calories in and calories out for the entire day. So, if you can eat balanced, keep the metabolism going strong, feel healthy, then it doesn’t matter too much when you eat. It matters how much you eat.

Where This Diet Could Fail

  • The authors claim that the types of food don’t matter too much. However, you can’t expect to eat 1200 calories of chocolate for your diet and feel amazing. We must continue to eat a balanced portion of fruits, vegetables, lean proteins, healthy fats, and a few healthy carbohydrates. The authors do support healthy eating with the 8 Hour Diet Power Foods, but they don’t want to restrict you.
    8 hour diet power foods

    Eight Hour Diet Power Foods

  • It can be tough to stave off hunger in the evenings. For example, if you start eating at 8 am, then you can’t eat anything past 4 pm. What are you supposed to do if you feel hungry again at 8 pm, and don’t go to sleep until midnight?
  • Many suggest waiting to have breakfast to help with this. But, research proves that breakfast is best for the metabolism if eaten within the first hour of waking.
  • Not suitable for those with unstable blood sugar.
  • The authors say that you only have to follow the diet 3 days per week. This seems odd to me. Why not follow it 6 days per week? 3 days is only about 43% of the time. This doesn’t seem too effective.
  • This is not a new diet idea. Intermittent fasting has been around for quite a few years now but has yet to gain popularity until now.

In the end, the positives and negatives seem to balance out. I have a feeling it will work for about half of the people who try it.

So, try the diet if you like, and let us know how it goes for you!

 By Mizpah Matus B.Hlth.Sc(Hons)
  • Mattson, M. P., & Wan, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of nutritional biochemistry, 16(3), 129-137.link
  • BLOOM, W. L., & AZAR, G. J. (1963). Similarities of Carbohydrate Deficiency and Fasting: I. Weight Loss, Electrolyte Excretion, and Fatigue. Archives of internal medicine, 112(3), 333-337. Link
  • Brownell, K. D., Greenwood, M. R. C., Stellar, E., & Shrager, E. E. (1986). The effects of repeated cycles of weight loss and regain in rats. Physiology & Behavior, 38(4), 459-464. link

263 Comments or Reviews

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  1. Rick May

    I have been doing this diet for a month now…I am diabetic and WOW how this has helped to lower my blood sugar. I am cutting back diabetic meds as my sugar levels drop so I dont bottomed out aas they say…I keep a list everyday of the calories, carbs and proteins I eat. I am a body builder and in the gym most days for 2 to 2.5 hours…I am amazed how stable my blood sugars are…and it is because of this diet…Thank you

  2. Jimmy

    So I do 8/16 (I guess). I eat breakfast and lunch and skip dinner (6am-2pm). I don’t see a problem with this but everywhere I see it suggests to skip breakfast… any thoughts?

    • Helen H

      I agree love my breakfast, can’t miss it so I’m with you in last meal @ 2pm, Helen.

  3. Phil T

    Ive been doing this for 20 years since i like to work out in the mornings. Wake up and have only coffee. By 9am im in the gym for an hour or more. First meal of the day is at 11am. A snack in the afternoon. Then eat dinner by 7pm. Go to sleep and do it the next day. I started this when i got about 25 lbs overweight when i was 30. I dropped thise 25 lbs and have been able to maintain with this regiment

  4. Kellie

    Hi there … just want to understand exactly how this works … so for example if I eat from 10am til 6pm (which is the 8hrs) do i then need to fast from the 10pm until 2pm and then I can eat again until say 10pm

    I’m confused when the 8hrs finishes wtc

    • Randy

      MY name is Randy. I started this diet @ 2 months ago. eat within a 9 hr window..usually between 12 – 9pm . I only allow myself 2000 calories Monday through Friday and on weekends i allow myself to eat whatever but still keep it within the same time period. I drink coffee with stevia sweetener (no calories) in the morning until my “eating time” is allowed. I started at 245 and am now at 212 lbs..a total loss of 33 lbs as of 8/5/18. I have not really done any major exercise but my job entails quite a bit of walking ( I do now own a treadmill and get on it maybe 2 times or more a week(depending on how tired I am hehe) THIS DIET WORKS! I was amazed at how fast I lost weight at the beginning. Now the pounds are a bit harder but still falling off slowly. I hope this helps anyone thinking of trying it. I had my doubts but now I BELIEVE….GOOD LUCK!

    • Rhonda

      you eat from 10 am -6 pm fast 6 pm -10 am

    • trish

      you would then fast from 6:01pm to 9:59 am

  5. teresa

    I’ve just started the 16.8 diet my window is from 2pm to 10 pm (due to work ) I’ve done this for a week and I’ve put on 2lbs !!! *I’ve been excersising every day as well so why haven’t I lost !!!!

  6. Auntie A

    I started this fast 3 weeks ago…So far I’ve lost 2 lbs a week…Not to mention the inches…60yrs young. . Getting lil exercise and feeling much much better!…Eat what ever I like…Just don’t pig out!…Use any time frame you like…Time wise…My window is 6pm to 10am..Like medication…For best results doing it the same time every day helps…Oh forgot to mention…I fast every day!…Set the alarm on my phone and just stick to it…Also, Just drink water if you are feeling hungry…I love water so this is easy…Try it!. ..I’ve tried It all..Couldn’t stick to anything…This is going to work for me!!!!

  7. Elo

    If i work a shift from 2 PM to 11 PM, should I stick to breakfast and then an early dinner, or what would be the best recommended strategy where compromise is minimum?

  8. Fay

    I have been doing this for about three weeks and have lost eight pounds. I find i sleep better than ever and food cravings have gone. It’s easy and i plan to eat this way for ever. Why not it works and i feel so well. Oh and i don’t do the exercise first thing but must aim to do this.

  9. Bill

    Is it better to exercise before your eight hour window opens or during?

  10. Lèon El patron Dos Santos

    Eat Breakfast Like a King, Lunch Like a Prince, and Dinner Like a Pauper.

    Get your bigger meals out of the way first. It’ll help with bloating and keep you fuller for longer.

    Alternatively, drink a pint of water before all meals.

    “never confuse thirst with hunger”.

  11. Pam

    After getting some negative results on my blood work, I started dieting on June 21. I am eating low-carb and counting calories (1200- 1400), but I am also eating in an 8-hour window. Based on calories intake alone, I should be losing about two pounds per week; however, I’ve already lost 14.5 pounds in 19 days. I haven’t lost weight at that rate since I was in my 20s (I’m in my 60s). I have to think the intermittent fasting is the difference. I also walk at least 30 minutes each day and drink about 80 ounces of water, but I’ve done that before and haven’t had the amazing results I’ve had since eating in an 8- hour window.

    • Paula

      Oh Pam you give me hope. I am 65 and put on 85 lbs in 5 years from medication. Tried everything. Nothing has worked. Been on 16:8 for one week and going to weigh in another week. So far, I don’t feel smaller but it’s an easy diet to follow. I’ll keep everyone posted

  12. Jules

    Will fast work 7 am to 3pm? Everyone seems to be starting much later. Would it help to swap starting hours occasionally?

    • susan

      I would say yes, it’s the fact that you’re not making your body work at digesting food for 16 hours, so the actual time you eat is entirely your choice. I am doing 10 to 6, but if I needed to would move the time frame. It’s the 16 hours that are important, so start at 7 am if you need to.

  13. Cris

    Here’s what I did,I start eating at 10 am,and I really get full (rice,viand,coffee and dessert) after that,I stop then eat again after 8 hours (6pm) In between I just drink water.I never crave or get hungry until 6pm.My question is,can I have a light snack during 8 hour window? Or can i still take lunch? This is my 8 day of IF but I noticed that I already lost weight.

    • Margaret

      These are the times, Im choosing, Yes, It does work!!!

      • Margaret

        Whoops, sorry, This was meant for the comment above yours mar

    • Kris

      I think you have this backwards. You are supposed to eat WITHIN the 8 hours. Not outside of it. It is 16 hours of fasting then 8 hours of eating. So you should eat a good amount of food within the 8 hours so you arnt hungry after!

  14. HollyH

    I’m trying this iv just started I do it everyday except Sundays and I’m excluding night I go to parties! Iv been on it a week it’s not too bad I drink juice when I feel hungry the taste makes me feel as if imy eating

  15. Chelsea

    Should the 3 days be right in a row or alternate days in between? And is there a benefit or lack thereof, just starting at 7 days right away?

Last Reviewed: January 25, 2018