Hi Dieter.

Question 1: Is it healthy or is detrimental to my health?

Yes, my opinion it is that is healthier to eat in a smaller window in the daytime, because intermittent fasting has many benefits, especially in the case of insulin resistance.

Some good graphical representations are in this article of Dr. Fung: Fasting Regimens – Part 6
https://intensivedietarymanagement.com/fasting-regimens-part-6/
The less insulin / time dependent (1 vs 3 red zones), the better for reversing insulin resistance.

Important is that your body to be well adapted to a 4 hours eating window, so daily 20 hours fast not to be a major stress factor to your body. If it feels stressful not eating in the evening (and you’ll have problems sleeping), you could try to adapt better to a 6 hours eating window, and maybe moving the starting hour around 11-12. You’ll have to test for yourself and see how your body prefers.

In my opinion equally important is that you have some days when you eat at your TDEE level. A constant intake at 1.200 calories could lower your metabolism and cause binge eating episodes and weight gain, and you want to avoid this.

I’ve also read that when-the-eating-hours-are is important for weight loss. If you have your eating window in the daytime you are losing more weight than having it in the evening. And the cause is that insulin release is greater in the evening, at identical meals.

This study I think it says it all: the study compared the effect of eating a large breakfast versus a large dinner: both groups ate 1.400 calories, BF group lose 8.7 kg, D group lose 3.6 kg. So yes, the time of your eating window is essential for weight loss.

“So what this study did was to randomly assign two groups of overweight women to eating a large breakfast (BF group) or a large dinner (D group). Both ate 1400 calories/day, and the macronutrient composition of each diet was matched – only the timing of the largest meal was changed. While both groups lost weight, the BF group was clearly superior for both weight loss and waist size (important measure of visceral fat) by almost 2.5 times (-8.7 kg vs -3.6 kg).”

Extras from Dr. Fung’s article: Circadian Rhythms – Fasting
https://intensivedietarymanagement.com/circadian-rhytms-fasting-17/

And here is the link for the whole study: High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women.
http://onlinelibrary.wiley.com/doi/10.1002/oby.20460/epdf

Another 2 studies I found in this article in The Washington Post: Why eating late at night may be particularly bad for you and your diet.
https://www.washingtonpost.com/national/health-science/why-eating-late-at-night-may-be-particularly-bad-for-you-and-your-diet/2015/08/24/ad8b85ac-2583-11e5-b77f-eb13a215f593_story.html

Extras:
“Two recent studies have shed new light on the potential impact of timing. In a study of 420 overweight or obese people published in 2013, those who ate their major meal after 3 p.m. lost less weight during a 20-week weight-loss program than those who ate that main meal before 3 p.m. — even when the amount they ate, slept and exercised was the same.

“This is the first study to show that eating later in the day . . . makes people lose less weight, and lose it slower,” even when the amount people ate, slept and exercised was the same, says the study’s lead author, Marta Garaulet, a professor of physiology at the University of Murcia in Spain. “It shows that eating late impairs the success of weight-loss therapy.” In the 2013 study, the early eaters lost 22 pounds, the late eaters only 17.

In a subsequent small study of healthy women published this year, Garaulet and her team showed that when participants ate lunch after 4:30 p.m., they burned fewer calories while resting and digesting their food than they did when they ate at 1 p.m. — even though the calories consumed and level of activity was the same.

What’s more, when the participants ate late, they couldn’t metabolize, or burn off, carbohydrates as well as when they ate earlier. They also had decreased glucose tolerance, which can lead to diabetes. (The two-week study did not track whether the women gained or lost weight.)”

Direct links to the studies:
1. Timing of food intake predicts weight loss effectiveness.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3756673/

2. Meal timing affects glucose tolerance, substrate oxidation and circadian-related variables: A randomized, crossover trial.
http://www.ncbi.nlm.nih.gov/pubmed/25311083

Question 2: If I go on it for awhile and then go off would it make me gain all the weight back?

The answer is: yes, could be, if your weight gain was initially caused by insulin resistance. Here is Dr. Fung’s answer to a similar question:
http://www.dietdoctor.com/permanent-effect-intermittent-fasting-insulin-resistance

Q: How permanent is the effect of IF on the insulin resistance? After you lower the insulin resistance through a regimen of fasting, is it sustainable or you have to do it for life?
A: It is not permanent. It’s like taking a bath. You can’t do it once and expect to be clean forever.

I’ve also read about a study (sadly I did not saved the source) where eating the TDEE calories in 12+ hours leads to weight gain, but eating them in ~6 hours (don’t remember exactly), the weight was maintained. And the reason is that as long the insulin levels are high (each time after eating something, no matter what), the body is in storing-fat-mode, and the fat burning is blocked.
Like in this graph, the green zones vs blue ones: How Insulin Works – Hormonal Obesity VII
https://intensivedietarymanagement.com/insulin-works-hormonal-obesity-vii/

You could also regain weight (due to binge eating) if you did not listened to your body (hunger) and forced a daily max 1.200 calories intake, having daily a large calorie deficit, instead of a cyclical pattern, with days at your TDEE level.

I hope my message answers all your questions about IF 20/4. Good luck!

PS: On a separate note I want to address the LCHF (Low Carb High Fat) solution for insulin resistance that seems for many to be the only choice, dietary speaking.

Here is the “Power: Fasting vs Low Carb” article from Dr. Fung’s blog: https://intensivedietarymanagement.com/power-comparison-fasting-vs-low-carb-fasting-26/
Extras: “Looking at total area under the curve, you can see that carb free diet can reduce insulin by roughly 50% but you can go another 50% by fasting.”

My opinion is that some persons can improve their insulin sensitivity (but not to 100%) having 2 options:
1. LCHF in a (x) hours eating window (let’s say 3 meals a day in 12 hours eating window)
2. Moderate Carb diet (with fruits and safe starches, maybe some beans etc – around 100-150 grams of carbs / day) but in a much-smaller-than-(x) eating window, to benefit from the insulin-lowering-effect of fasting daily for a much longer period. (let’s say 2 meals a day in a 4 hours eating window, and fasting for 20 hours).

So I think it’s important to look at the “total area under the curve”, how Dr. Fung says, but for the whole day, 24 hours, not necessarily at every meal / every hour of the day. Again, this is just my own point of view, which could also be wrong, but I think it has his merits to be tested, if someone just can not stick to a very low carb diet.

Yes, LCHF + fasting have together a greater effect on insulin resistance, but my opinion (which I do not wish to debate) is that strict LCHF it is not a healthy choice on long term. Details in the extras below, plus the risk of binge eating associated with any form of long term restrictive eating (psychological factors).

Extras: Chris Kresser and Tom Naughton in a review of Perfect Health Diet, Paul Jaminet.
http://www.fathead-movie.com/index.php/2014/04/28/safe-starches-and-the-perfect-health-diet/

“In the cyberspace crowd of health-oriented blogs and Facebook groups, I noticed more and more people saying they developed problems on a strict very-low-carb diet – low thyroid function, cold hands and feet, high fasting glucose, dry eyes, etc. – which went away when they added some “safe starches” back into their diets as prescribed in the Perfect Health Diet.
….

That peak health range is the amount of glucose our bodies require on a daily basis — somewhere in the range of 100 to 150 grams. It’s this chapter of the book that started all the hubbub over “safe starches.” Yes, your body will convert protein into glucose – even if it has to raid the protein stored in your muscles to do so – but the Jaminets argue that forcing your body to meet its daily glucose requirement through gluconeogenesis can eventually cause the health problems Chris Kresser described seeing in some of his patients: slow thyroid, dry eyes, cold hands and feet, low energy, weight-loss stalls, etc.
…

I see a fair number of patients in my practice struggling with symptoms like hair loss, cold hands and feet, plateaued weight loss, low energy and mood imbalances after following a VLC diet for several months. In many cases they adopted this approach to lose weight, which was successful – at least to a certain point. However, others were not overweight to begin with and simply chose to eat VLC because they got the impression that “carbs are bad”, even for people without metabolic problems. I believe many of these issues are related to the decrease in thyroid hormone levels seen on VLC diets.

In cases where there is no significant metabolic damage, when I have these folks increase their carbohydrate intake (with starch like tubers and white rice, and fruit) to closer to 150g a day, they almost always feel better. Their hair loss stops, their body temperature increases and their mood and energy improves.

For people that are overweight and are insulin/leptin resistant, it’s a bit trickier. In some cases increasing carbohydrate intake moderately, to approximately 100g per day, actually re-starts the weight loss again. In other cases, any increase in carbohydrate intake – in any form – will cause weight gain and other unpleasant symptoms. A different approach is required for these patients.

As always, there’s no simple answer and no one-size-fits-all approach. If I could leave your readers with one point, that would be it.”

Hi Mossa and welcome:

Just going 24 hours without eating means little. What counts are the calories you eat before and after the 24 hour period. So eating 600 does not make the plan work ‘better’, it is just that is all that is eaten during the 36 hour ‘fasting period’, so that cuts calories out of your diet and you have a better chance of losing weight.

This will answer most of your questions: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

Good Luck!

@adaline – Totally awesome post!!!!!!

@dieter – You are already losing weight so you already know how to control your diet. IMHO, adding fasting will only improve your weight loss. Also fasting can help improve your metabolism, although you might have to do it a lot more than you want.

Personally I think the source of the calories is profoundly more important than the actual amount of calories. For example refined sugar isn’t that high in calories but it probably is the number one contributor to belly fat. Fat sources are much higher in calories, more than double but they are much more filling than sugar. Sugars and foods that easily break down into sugars tend to drive hunger much more than fats and fiber. However there is a balance and what works for may be different that what works for me. For example while I avoid refined sugars I do eat a lot of whole fruit. When I can I’ll eat fruit vs a sugar based desert. When I do eat refined sugars I’m aware of what I’m doing than that is where I use portion control.

Several years ago my doctor had me cutting back on carbs. That was actually helpful when I was trying to use calorie restriction, not so much because of the calories but because it seemed to improve the benefit of the reduced calories. Later I found out that it was really the refined sugars driving my hunger and once I got my refined sugar consumption less than 20g / day I started losing a lot of belly fat. I was even able to increase the amount of carbs I eat, but I still limit carbs mostly because I prefer other foods now.

Anyway I got down to 86kg and plateaued. I started 5:2 found it easy and after six months I’m down under 80kg. I’m fasting though more for the hormonal benefits. Many on the 5:2 diet don’t do pure fasts as they allow themselves 500 to 800 calories a day. When you do that, probably the overall calories drive things more. I don’t eat while fasting although I do sometimes allow sugar free gum or other very low calorie things. (Total < 25 calories / day.) That isn’t that easy because even a cup of coffee really has a couple calories. Things aren’t really zero calorie just close to zero. However as I’ve fasted I’ve greatly increased my consumption of water which is really calorie free! 🙂

Sorry to be long winded. I think adding fasting will help and fasting is very flexible. Set up the pattern that works for you and then you’ll probably be successful.

I’ll let you off this time dykask. The 7500 steps allows you to have a donut. Not that Im advocating that you have a donut, just trying to place it into perspective.