The Dangers of Intermittent Fasting

IF appears to not be that great…

However cutting calories at night appears effective.

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I think the basic idea is that night time is a good time for repair and maintenance. Hence if you eat in the evening eating earlier and less is a good idea.

I tend to have a salad (with some corned beef) around 5-6pm


IF has helped me to cut calories. Which is easy for me when I have my first meal at lunch time.

I don’t know If IF is better, worse or equal to other ways of cutting calories? But If works, as a strategy to cut calories, for me.


that’s just not true, there are other benefits to intermittent fasting, eg not eating for a while gives your teeth time to remineralise


I feel good when not eating breakfast. I have a clearer mind, more energy and a better mood. So for me IF not only made me loose 6 % bodyweight but is is a healthy strategy for my general wellbeing. .


I didn’t really know I was IF every day since I was 6 :face_with_open_eyes_and_hand_over_mouth: until some years ago a friend started to ask me if I am on IF diet and I googled it. Since I was a child I wake up not feeling hungry at all, almost morning sickness… My husband is joking i have naturally high GLP-1 levels. I rarely feel really hungry, it usually is just a wish to eat something good. I really get hunger, what probably is normal, when my BF drops below 14%. I start working late, usually afternoons, so I have a really late breakfast/lunch and small lunch and dinner. Sometimes lunch is just a snack. This is how I eat for the last 40 years and it suits me. If I eat something in the morning, especially when traveling I feel crappy all day.


He cites the Cochrane review below, for authority:

This is what the Cochrane review said:

Our confidence in our results

We are not confident in our results. We found limitations in the ways that the studies were designed, conducted and reported; and in some studies, the results varied widely, or were not consistent. Our results are likely to change if more evidence becomes available"

He also cites Kaeberlein’s study found below:

This is what that Kaeberlein study said:

Unfortunately, it is not currently possible to know whether CR-like diets impact biological aging in people (Text Box 2). Unlike mice, controlled studies would need to be performed over many years to assess long-term benefits for lifespan and healthspan in humans. The recent development of various “aging clocks” that accurately predict chronological age, and may soon be useful for predicting biological age, offer the possibility that this question may be addressable in the relatively near future (64). For now, however, the data remain correlative.

One line of evidence often cited to support anti-aging effects of CR in natural human populations comes from studies of Okinawans, who inhabit a small Japanese island and smaller islands in the surrounding archipelago where the indigenous population historically consumed about 20% fewer calories than mainland Japan. Traditional Okinawan diets are very low protein (9% of total calories) and high carbohydrate (85% of total calories) (65). Historically, Okinawans enjoyed the longest life expectancy at birth and highest centenarian prevalence in the world, with remarkably low rates of age-associated diseases, like cancer, heart and cardiovascular disease, and diabetes (66).

Another line of evidence for health benefits from CR comes from the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE) studies. These are a series of controlled clinical trials in normal and overweight adults subjected to a 25% reduction in caloric intake over periods ranging from a few months to two years. The results of these studies were generally consistent with improved clinical biomarkers of health such as decreased weight, enhanced insulin sensitivity and glucose tolerance, and improvements in major cardiometabolic risk factors (67).

The CALERIE data are further complemented by uncontrolled studies of people self-practicing CR. Data from individuals self-practicing CR are also consistent with improved age-related health measures including reduced weight and fat mass, lower blood pressure and other markers of heart disease, and improved glucose tolerance and insulin action (68, 69).

I always go to the source studies, because some bloggers are not too faithful to the studies they cite.

Two channels stand out to me, as faithful to their sources. They also explain better than my personal understanding, reading their sources - Eleanor Sheekey and Michael Lustgarten.


I posted a similar comment in his channel. It was not published. I posted another critical comment on another video, months ago. It was not published, either.

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I put the video up here to inspire a lively debate. It worked. :slight_smile:

Actually I don’t know how I feel about IF. Since Rapamycin is a fasting mimetic, I think we may be getting most of the potential benefits that way.

For me, IF doesn’t seem necessary, but I may try it once I retire. Impossible to do that while working…

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And it gives your pancreas a rest.


Attia cites no study. He also harps on extreme TRF (OMAD 2:38). And he admits he is making up the numbers ('m making this up" 2:06 "I’m kinda making these numbers up."3:30)

His bottom line is “Then you gotta make sure you’re not restricting protein, and you’re thinking about when you can refuel in relation to exercise.” 3:49 to 3:58).

That does not seem to be anti-TRF, just cautionary about protein intake in relation to muscle mass. Misleading title again.

Pam Taub, MD, of the UC San Diego School of Medicine has done a study with 150 firefighters, cited below. The fasting window is not extreme - 14 hours. (10 hour eating window).

The new findings, published in Cell Metabolism on October 4, 2022, determined that time-restricted eating within a 10-hour eating window was not only feasible, but also helped the firefighters significantly decrease their VLDL, or “bad” cholesterol, improve their mental health and reduce their alcohol intake by roughly three drinks per week.

“Our study showed that shift workers with high blood pressure, blood sugar or cholesterol can benefit from time-restricted eating,” says Satchidananda Panda, PhD, co-corresponding author of the study, Salk Professor and holder of the Rita and Richard Atkinson Chair. “It’s not a pill, but a healthy habit that can significantly reduce these three risks of disease without any adverse side effects.”

The study found that time-restricted eating also significantly improved blood sugar and blood pressure in firefighters who had elevated levels at the start of the study. The researchers concluded that time-restricted eating may provide even greater benefit for those at risk for cardiometabolic disease and other chronic diseases.


Attia may be referring to this study of resistance training subjects.

There was a decrease in testosterone (17%), and some decrease in muscle, for the TRF group, and a gain for the non-fasting group.

A significant time–treatment interaction (P < 0.001) was observed in muscle cross-sectional area (CSA). No significant effect was found between baseline and 2 months of intervention; however, at the 12-month assessment, arm CSA in the TRE group decreased by 4.31% (P = 0.003, d = −0.47) and thigh CSA decreased by 2.90% (P = 0.03, d = −0.37), whereas CSA increases of 11.87% (P < 0.0001, d = 1.15) and 6.94% (P < 0.0001, d = 0.47), respectively, were observed with ND.

But the smaller muscled group was stronger. Their bench press and leg press improved more than the non-fasters.

These changes in muscle mass did not affect muscle strength measures on 1RM test for the upper and lower body. After 12 months, both groups significantly increased their bench press performance (TRE: +15.42%, P < 0.0001, d = 1.02; ND: +10.82%, P < 0.0001, d = 1.64) and their leg press strength (TRE: +15.24%, P < 0.0001, d = 0.77; ND: +14.21%, P < 0.0001, d = 1.84).

So despite an increase of 11.8% in the arm for non-fasters, and a decrease of 4.31% for the TRE group, the TRE group improved their bench press by half of the improvement of the non-fasters 10.82% versus 15.42%.

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An in-depth review of the pros and cons of IF:-


That does not seem to be anti-TRF, just cautionary about protein intake in relation to muscle mass.

Keep in mind that it takes some effort to reach the recommended amount of daily protein, even when eating 3 times a day (without resorting to drinking protein shakes) . At his age and his fitness level , he seems to be far more worried about muscle loss, because it’s hard to regain it. So it makes sense for him to focus more on building muscle, and TRF slows that process.

Anyway, that’s my best guess.


I think ‘dangers’ is a strong word. I feel like there are many conflicting views on this topic. Some channels overemphasise the benefits as well.

As usual, the truth probably lies somewhere in the middle. IF can be good, bad or indifferent - depending on the person/situation/environment/countless factors.

I personally have found that IF has been productive and counter productive towards my goals. There have been times in my life I have forced IF even when I didn’t feel great doing it - and lost too much weight/quality of life suffered. At that time, I thought ‘no pain no gain’. Actually, I just lost too much muscle and had far too high cortisol.

On the flipside, I have seen great benefit from IF at other moments. The gut rest and mental fortitude have both done me a world of good at certain times.

I am now learning how to listen to my body better rather than being so regimented with IF. Understanding when to fast and when not to fast is probably optimal for me and every day looks somewhat different.


Yes, this is sometimes quite difficult if you want to practice some CR as well. I try to eat around 2000 kcal in 3 meals, each around 40 grams of protein and it gets difficult to get to that number without protein centric meals… today I had shakshouka, piece of sourdough, some kiwi and skyr with a tablespoon of homemade granola for brunch, skipped snack and had slow roasted pork with onions and polenta for early dinner with a desert of raspberries and little whipped cream. A little over 2000 kcal and 120 g protein on the dot. Had also some collagen, eaa and chlorella drink before brunch.


I prefer transcripts if available. Below is the transcript.

The study he refers to is below:

There were 116 participants. There were 150 in Pam Taub’s. The JAMA study subjects were overweight or obese. The Pam Taub study involved firefighters (generally fit). The demographic in this forum, I believe is not obese. So Pam Taub’s study is more relevant to us than that JAMA study.

Peter Attia’s bottom line, which appear in bold font:

So in other words, eat a couple of meals during that eight hours, but make sure that the quality of those meals is at its finest .

Talk about stating the obvious.

Lost interest in this guy. No more Peter Attia videos for me.

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What title is misleading?

Where is he referring to a study?

Hmm, I think I will try doing a lot of protein shakes with IF, maybe 4 scoops a day. And two meals on top of that (one meal at the start at the eating window, one at the ending of it).