In this video Doctor O’Donovan explains 16:8 intermittent fasting – a popular type of intermittent fasting that involves fasting for 16 hours and an 8 hour eating window. In this video he explains what 16:8 fasting is, what time windows you might want to choose for your fast, food groups to consider and benefits and drawbacks of intermittent fasting.
Intermittent fasting is when you alternate between periods of eating and fasting. This type of eating is often described as “patterns” or “cycles” of fasting.
Intermittent fasting isn’t about starving yourself – it’s about cutting way back on calories for short time periods. The belief is that your body becomes satisfied with smaller portions while also reducing cravings for unhealthy snack foods. That is, as long as you maintain a healthy diet while trying it all out.
In the video we cover:
00:00 – Introduction to 16:8 Intermittent Fasting
01:08 – Picking a time window for 16:8 fasting
02:42 – Some foods and drinks to consider during 16:8 fasting
04:07 – Potential benefits of 16:8 intermittent fasting
05:00 – Potential drawbacks of 16:8 intermittent fasting
06:14 – Top tips
Many diets focus on what to eat, but intermittent fasting is all about when you eat. With intermittent fasting, you only eat during a specific time. Research shows fasting for a certain number of hours each day or eating just one meal a couple days a week may have health benefits – for example for loosing weight and for better control of diabetes.
Further information:
My other popular video covering an OVERVIEW of IF:
What supplements and vitamins can you take when doing IF? :
NHS information on Intermittent fasting:
Patient Information:
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The video is intended as an educational resource only. The information within this video or on this channel isn’t designed to replace professional input, so if you have any medical issues please consult a medical provider. No professional relationship is being created by watching this video. Dr. O’Donovan cannot give any individual medical advice. All information should be verified for accuracy by the individual user. Dr O’Donovan accepts no responsibility for individual interpretation of data, although it is always accurate to the best of his knowledge at the time of the video being published. This is an EDUCATIONAL video. Images are used in accordance with fair use guidelines.
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My best friend recommended this approach to eating, with the goal of eating cleaner foods, having more energy and achieving healthier outcomes. That may sound boring and restrictive. Anything but!!! I am enjoying drinking water more, eating delicious whole foods (new recipes!) and knowing when to stop eating. The eating window of 12pm-6 pm helps me stop and analyze why I want to eat. This has helped me identify emotional eating patterns. I am now facing it and getting help. A byproduct of this lifestyle is my average weight going from obese to “overweight.” (Down 26 pounds) I am continuing this lifestyle to get to my ideal weight. I feel so much better focusing on stewardship of my body, vs. my weight. I can’t recommend this plan enough!
Is it okay for people with hiatal hernias?
I did fasting too …7 night I ate sometime I ate 9 evening I dnt know if I'm doing right but the whole day I dnt eat food just water cofee
I thought the whole concept was reduced carbs ?
Shutting off the food noise is my hard part. Having a “strong will” simply isn’t enough.
any comments from 2026?
I have been doing an 18:6 eating between 12 noon and 6pm. So far (over the last 21 days), I have lost 10 pounds
This is my 5th day its not very hard ,i had my dinner at 9 pm yesterday and today i have my lunch at 1 pm .
This is absolutely a game changer . I wasn't mindful of my night snacking , maybe a popcorn a bowl of cereal or. Pbj sandwich . Seems pretty innocent but coupled with breakfast was keeping the weight on . I'm dropping faster than expected , also I'm past the hunger threshold you experience the first 3 -4 days . A good tip is to go to bed at a decent hour in the beginning to alleviate the growlies. I drank green tea later in the beginning in evenings .
I overall like this plan but not some of the extremes that some start moving toward are a concern. I like that you encourage healthy eating because some start this plan and think the magic is that they fast for a period of time and disregard the foods that they eat during the eating phase
Can i include coffee?
I started while on vacation, it was easy because I had stuff to do around the house, ate at 12 like something for lunch and dinner, I haven’t lost any weight yet, I don’t have high blood pressure, borderline diabetes and high cholesterol. I refuse to get on statins because of the side effects like mine was stomach pain. I’m hoping I can stick to it when I go back to work, there’s temptation there. Pray for me!
16:8 was the only protocol that stuck for me because it's basically just skipping breakfast. i use AllyFast to keep my window honest (i built it) – seeing the fasting hours add up makes it a lot easier not to break early.
I started today day 1
Unfortunately, I have to start fasting at 3pm because I need my morning coffee with cream
I'm an endocrinologist and I don't usually recommend it to my patients because they tend to overeat in that 8-hour window. The moment they give up on fasting, they gain weight because they keep eating the same way, without an intake window. Counting calories and macros is still the best way to do this, because you are not forced to eat 130g of protein in 8 hours and can stretch it out in a 24h period. Those 8 hours become an eating disorder if you do it long enough….it's your only mission, and the other 16 is thinking what you'll eat in those 8 hours. This is not dieting, this is not a change of lifestyle, this is a cage.
i will start mine today, wish me luck.
I naturally do 11-7. Things were decent until menopause hit and then I gained weight out of nowhere. It’s so frustrating.
Extremely useful. Thsnk you doctor
Fingers crossed it’s been 5 days to shift menopause weight!
I have done it for 10 months. No weight lose. I drink my fruit and vegetables. Eat eggs and fish and toast. Drink coffee and water. Doesn't work.
Did for one month and lost 5 kg in one month and on my 2nd month now
Best is determined also on when you sleep at night. I wouldn’t recommend starting the fast right at bed time. Best end the eating window 2-3 hours prior. Me personally I go from 6pm – 10am fasting. Give plenty of time to digest, go for a walk after dinner and you’ll be on your way to good health
I started the 16:8 intermittent fasting about two months ago and the hours I eat are from 4 pm till 12 midnight. I have been bedridden with a spinal Disability and badly damaged spinal cord in hospital bed at home for the last six years and I live with chronic pain. I’m on so much pain relief medication which I hate taking but I am allergic to anti-inflammatories plus I’m taking blood thinners. And I suffer with a lot of inflammation as well as chronic nerve pain. Anyway, I put about 10 lb in weight on over Christmas because I usually calorie count and don’t go over 1200 cal a day because I’m not able to exercise. So I thought I would try this and get back into my calorie counting and eating healthy.. but the biggest benefit I have found from this apart from the fact that I’ve just lost half a stone which is really good for me considering I’m stuck in bed is it has helped my pain and cuts the inflammation pain down by about 50% which is huge for me🙏🏼 I didn’t even know it could do this!
No snacking…Bad information.
I'm in day 4, & I feel great today. First 2 days were rough. Headache & fatigue…But today I'm good. Body is adjusting
10 am to 6pm changed my life, along with conscious breathing, stoping at 6pm gives you enough time to digest and prepare to sleep at 9pm to 10pm, great for pineal gland too
Im on week two i done a 24hr fasting on a monday then started the 8/16 fasting its been nearly 2 weeks im up at at 4 and im asleep by 8pm so my eating window is 8am to 4pm I love it best thing I have ever done feeling really good.
I typically have a cup of coffee, about 16oz, with 1/8 cup creamer. Sometimes I don’t even finish my cup because I’m so busy running around.
I don’t eat breakfast or snack. I take my lunch about 2:30 pm and I always have two fruits and a veggie along with a cup of yogurt with chia seeds and a bag of salad. When I get home at 530 I eat the left overs from my daughter’s lunchbox, which is all fruit and veggies and nuts and maybe a left over half of a peanut butter sammich. I don’t typically eat after 7. I don’t loose weight, I need more movement for sure.
Thanks
I feel like hakf the video is a disclaimer to protect from lawsuits😂. Going for the 12 8 but still gotta have my coffee woth a wee bit of sugar or I will die
I just started 3 days ago 21st February 2026.. lets wait for 2027..check comment
I started a week ago I eat 12-8
I have tried to lose 4-5kg that had creeped up on me in-between an accident an menopause. I tried a number of things: to no avail (despite lots of exercise, including 9 marathons). What seems to be working (for now) is a loose intermittent fasting scheme, where I eat between 11am and 7pm (more or less). In-between, I have not gone zero-calories entirely – I will haves some milk in my morning coffee or evening tea; if I'm hugry after 2h in the swimming pool in the evening, I will actually eat something small (a yogurt, a soup with a piece of bread). I simply try not to eat or drink any significant amounts of calories and nothing heavy on my stomach after 7pm, even when I exericise a lot, even when I work late. Evenings are the harder part for me; skipping breakast (or having it at 11am) is not a problem at all, as I often exercise in the morning and have always done so fasted anyway. For now it seems to work, and the stubborn fat on my midsection seems to be on the way out. I am not sure how things will work out in 2 months from now when I'll be in the middle of marathon training once again and will need to up calorie intake alongside increasing mileage. But I'm confident that it should still work. On the positive side, 11am-7pm fits my natural rhythm well; it also works when I'm occasionally around people who eat at very conventional hours (such as lunch at 12pm – which I never do if by myself); and it works with my sometimes quite intensive exercise as well. The downside is that's it a bit complicated, it means that I sometimes would need to carry three meals with me ('cause else I won't find decent food when I need it, or it won't be the right kind). Anyway – for now I'm trying to stick to it more or less, not being dogmatic about it, just trying to not eat late in the evening any more even when a bit hungry. When I spent some time with my elderly and diabetic mum, I noticed that a longer fasting period overnight actually made me feel better, but as soon as I was back to my daily life, I veered off it again – I'm now trying to keep this, my metabolism is happier that way.
Starting today
Ok so I am late. Can you exercise with this. Also how much do you eat on this.
I've been fasting for 4 weeks
I don't eat all day as I'm really busy and I have a meal around 6pm and a light supper around 9 or 10 pm
I drink water and clear drinks all day. I cook meals from scratch and include fresh vegetables berries and protein.I feel better in myself but haven't lost a single pound
What am I doing wrong???😢
7 hours after work for me. I guess technically its a 17/7
So can I just eat one meal a day dinner and it still be considered fasting just eat one decent meal at dinner time and nothing else at all but water
I have had best results with the 8/16 by taking a two week break every three months and eating normally. Then go back to the 8/16 for three months. And once a month throw in a 24 fast. I think keeping the body from getting used to it is the key to weight loss. I've lost 103LBs in 14 months.
I'm 82,9.I aim to be 69 kg in April . I'll come back to this comment to give an update
January 19th 82,9kg