Does 16:8 work?

This topic contains 17 replies, has 6 voices, and was last updated by  Vet272 8 years, 1 month ago.

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  • I read somewhere that 16 hours of fasting followed by an 8 hour window during which 2 normal meals were allowed was a method that could give equivalent results to 5:2 ( Everyday schedule )

    Can anyone fill me in on this? I find it easy to do,(3 weeks so far) but unfortunately I haven’t lost any weight!

    Any scientific studies with references on this method?

    It seems unlikely that you’ll get the same results, but there does appear to be a benefit of extending the non-eating time!

    http://www.bbc.co.uk/programmes/articles/zBx3JZJCKfNBrWgT0Qyj93/the-big-experiment-could-i-lose-fat-just-by-changing-my-meal-times

    Hi Vero and welcome:

    16:8 is also known as the 8 Hour Diet. I think the book came out in 2013 and was very popular for awhile and then faded. The book claims that you can eat as much of anything you want and as long as you eat it all in 8 hours or less you will lose 20, 40, 60 or more pounds – even if you only do 16:8 three days a week. According to the book, the secret that allows you to eat, say, 3000 cal. a day when your TDEE is 1800 and still lose weight, is that by going 16 hours without eating any food your body will go into a ‘fat burning mode’ that will counteract all of the calories you are eating. People soon found it didn’t work, but interest in the diet has been revived as it has been rebranded as an intermittent fasting diet.

    Today, knowledgeable people know the claims of the book are inaccurate. 16:8 has become a description of when people eat – they eat in an eight hour eating window. The only way they lose weight is if they eat less than their TDEE in that window – if they eat more, they gain weight. There are no dietary ‘rules’ that go with it, it is anything you want it to be. Basically, it is a 7 day a week lower calorie diet (if you eat less than your TDEE each day).

    As there are no calorie restrictions or food requirements that come with the 16:8 name, anyone can say they are following 16:8 and you will have no idea of what they are talking about unless they also describe what, how much and how often they are eating during their 8 hour eating window. For instance, it is not unusual for people on 5:2 to eat only one meal on their diet days. That could be described as following 16:8, but it could also be described as following 23:1, 19:5, or 12:12 – all equally meaningless. They could be eating 500 cal. at that meal, or they could be on the warrior diet and eating 2500 cal. – although hopefully not on a diet day, but you won’t know by the name.

    There is a recent TV experiment going around that indicates there might be some benefit to eating in shorter time periods. However the experiment was hardly scientific. The people involved each had different diets and different calorie intakes. No weight loss was reported for either the ‘control’ group or the 8 person group on the restricted eating regimen. The benefits found could easily be attributed to factors other than not eating an additional three hours a day, including ‘different’ eating by the group that had the restricted window – they were only tracked by how much they ate. There is no way to know. Pretty much a meaningless exercise from a scientific standpoint, but good TV. However, it does highlight why some people like 16:8. Some people feel it helps them not snack as much, so they eat less. The concept of the window seems to help them focus on when and how much they are eating and by doing so helps them control how much they are eating. My observation is that if people start 16:8 for weight loss, they like it at the start, but within a month or two give it up because they aren’t losing weight and they don’t like having to arrange their lives by when they can eat.

    There are no other studies I am aware of that show any benefit of following an ‘eating window’ way of eating. But there are no studies that show it is harmful, either. You might see if there are any 16:8 forums or websites that can help you decide which method you like best.

    Good Luck!

    Well, Vero, as you can see, Simco really really hates 16:8 🙂

    I like it, for weight maintenance though rather than loss.

    I suggest you try it and make your own mind up.

    The opinions of other posters are really neither here not there (and yes, while Simco’s posts sound authoritative, it is just the opinion of another (albeit generally well-informed) lay person).

    The answer to your question is there are no scientific studies showing that 16:8 works or doesn’t.

    The overall idea may sound valid but the only way to lose weight is to consume less energy (calories) than you expend. I gave 16:8 a try and it didn’t work for me. The simple reason being I ate more in the eight hour window and two meals than I expended in the 16 hour not eating period. Heck I can consume more in an hour than I expend in a day.

    Some people find it beneficial it has to be personal. If it doesn’t work then do 5:2 it is proven to work for weight loss.

    Thank you QuietOne, HappyNow and simecoeluv for your replies. I assumed that the 16:8 implied reducing daily intake by a third, otherwise it would not make sense. Surely this is the same principle as the 5:2 arrangement, but easier to do, isn’t it?
    One thing I am not yet convinced about is that with intermittent fasting the body doesn’t reduce its metabolic rate. Why not? This was the problem with the Atkins diet. Atkins was the only diet that ever worked for me, but of course as soon as I fell by the wayside my resting metabolic rate dropped to 1300kcals per day and so I put all the weight back on with more.
    Looking forward to reading more of your interesting posts.

    Hi Vero:

    Your resting metabolic rate is irrelevant for weight loss. TDEE is quite important.

    If you look at any TDEE calculator you will see no input for what or how much you eat. That information is unnecessary to estimate either TDEE or BMR. That also means that information does not affect BMR or TDEE.

    Very little affects BMR – not even exercise. What does affect it is weight loss or gain – BMR goes down or up materially with those factors.

    Although Dr. Atkins speculated that there might be a ‘metabolic advantage’ by eating a high fat/protein diet, it was never proven. The diet neither increased nor decreased the person’s ‘metabolic rate’. Research shows that people following the Atkins diet are eating a low calorie diet and the reduction in calories causes the weight loss, as is the case with all successful weight loss diets.

    For the same reasons, 5:2 does not affect the BMR except by causing weight loss. Simply eating less has no effect on the BMR or TDEE at all.

    Good Luck!

    one of the better explanations of BMR can be read https://www.acefitness.org/certifiednewsarticle/2882/resting-metabolic-rate-best-ways-to-measure-it-and/

    BMR is measure in a resting post digestive state. RMR isn’t. BMR reflects very little on weight change down or up

    The biggest change to BMR is when you lose weight or gain it

    ie. 5.7 male 55 sedentary weight 225 pounds BMR 1798 Calories TDEE 2158 Calories
    5.7 male 55 sedentary weight 151 pounds BMR 1463 Calories TDEE 1755 Calories

    TDEE counts BMR not so much

    Vero,

    If to you 16:8 means skipping breakfast and then not compensating by eating more later, you will have ‘saved’ your breakfast calories. That may or may not be one third calories. For me that would be perhaps 400 calories ‘saved’, which is a 1/4 – 1/5 TDEE. Over the longer-term, this should result in weight loss. So in this scenario you are in the realms of daily caloric restriction. However, it is still possible to overeat in an 8 hour window. So it’s really going to depend on whether you’re happy restricting yourself on a daily basis.

    The beauty of 5:2 is that you don’t need to restrict every day, only 2 days out of 7. So for most people in terms of compliance it’s much simpler.

    In my experience, 16:8 can be sufficient for weight maintenance (and possibly weight loss over longer time periods; unfortunately when I was my lightest as an adult, and an inadvertent 16:8er, I wasn’t monitoring weight or exercise or calories…); 5:2 plus 16:8 plus no added sugar/ low refined carbs definitely works for me for weight loss.

    Hello HappyNow, thanks for your views. I am going to try 5:2again, because the 16:8 method did not give any results for me. I think 5:2 is a type of on-and- off Atkins, because it seems to depend on the few hours of ketosis produced if you stick closely to the fast days.

    I am very grateful to all who have replied to my post. Any new information would be welcome.

    Does Michael Mosley ever look at the blogs I wonder.

    Hi Vero,
    Michael has a programme called trust me I’m a doctor available on bbc I player. The research is now compelling on how good for you eating in a small window and fasting the rest.
    If you’d like to email me, I could go into greater detail. I’ve list 16lbs since 1/1/16

    Hi Vet272, that’s a really impressive loss. Do you mind me asking what eating window you use? Any advice? Thanks.

    Hello Vet272,
    I would really like to know how you lost your 16lbs in such a short time. I was also very excited about 5:2 when I read the book and watched the show on Horizon, but sadly it doesn’t seem to work for me, at least not noticeably so I would be delighted to know how you did it.
    Vero

    Hi Vero:

    I understand from one of your posts on another thread that you lost 1 kg in 6 weeks. That means the diet does work for you. One year from now you will be down about 20 pounds if you keep eating the way you are.

    If you are losing too fast, just eat more on either your diet days or your non diet days.

    If you want to lose faster – well

    The less you eat, the more you lose!

    Good Luck!

    Unfortunately I can’t get BBC iplayer because I live in Switzerland.

    Hi there.
    I’ve just weighed in and I’ve now lost exactly 20lbs since January 1st.
    I fast from 11am until 7 pm although I’m usually not hungry after dinner at 530 so might naturally stop then.
    I’m less drawn to carbs now, consequence of fasting? But have noticed I eat more protein,again not consciously.
    I throw in 2 full day fasts a week. I only drink lemon/mint tea and water on those days.

    Hope that helps Vero and zen

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