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So for these reasons, I am thankful to Alan Aragon for the aptly titled 'Intermittent fasting: After over a decade of research, where are we today?' in which he writes about the current state of affairs of intermittent fasting. The article appeared in the December edition of the Alan Aragon's Research Review (AARR) which I have been a subscriber of since the first issue.

I asked Alan for permission to publish the article on my site, as I had a few comments on the content therein, and housed no doubts that our readership would be interested in taking part of it all. You'll find that most of my thoughts doesn't have to do with the article itself, but rather with some of the statements and issues raised.

Alan has previously published A Critique of the ISSN Position Stand on Meal Frequency on this site. If you enjoy reading about nutrition and exercise with a scientific twist, check out Alan Aragon's Research Review.

Now enjoy this article, folks. You will find my comments prefixed with MB after the relevant paragraphs below.

Intermittent fasting and body composition: After over a decade of research, where are we today?

Speaking of decades...

The last time I wrote an article about intermittent fasting (IF) was almost a decade ago. A rich body of research on the topic has been published since then. The ongoing interest in IF is not surprising, given its mystique that’s wrapped in ancient spiritual origins, all the way to its modern applications to clinical and aesthetic goals. The aim of this article is to bring the reader up- to-date on the scientific findings, with a particular focus on comparing IF regimes with conventional/linear dieting. After all, the question is not whether IF works – it obviously does, as does any mode of caloric restriction. The question is whether it works better than conventional dieting for improving body composition, and if so, to which contexts can we apply it.

Variations on a theme

Let’s get some labeling/classification aspects out of the way. In the literature, the broad categories that I call linear and non- linear dieting have been called daily caloric restriction and intermittent caloric restriction, respectively. They have also been called continuous energy restriction and intermittent energy restriction. The intermittent category (what we call IF) can be further divided into three subclasses (1):  alternate-day fasting (ADF), whole-day fasting (WDF), and time-restricted feeding (TRF).

Alternate-day fasting

The most extensively studied IF variant is ADF, which typically involves a 24-hour fasting period alternated with a 24-hour feeding period. Complete compensatory intake on the feeding days (to offset the fasting days’ deficit) does not occur, and thus total weight loss and fat loss occurs on ADF. Lean mass- retention has been an intriguing effect of ADF reported by Varady et al (2-4). Lean mass loss in ADF conditions has also been observed by other investigators (5-7). However, the latter effect might be attributable to more severe energy deficits. The more lean mass-friendly The ‘fasting’ period in the Varady model is actually an energy-restricted period (~25% of maintenance requirements, typically in the form of a single meal at lunchtime) alternated with a 24-hour ad libitum (as desired) feeding period.

On the note of alternating fasting and feeding periods of the same length, alternate-week energy restriction (one week on ~1300 kcal/day, one week on the usual diet) has only a single study to-date, but is worth mentioning since it was as effective as continuous energy restriction for reducing body weight and waist girth at 8 weeks and 1 year. (8)

Time-restricted feeding

TRF typically involves a fasting period of 16-20 hours and a feeding period of 4-8 hours daily. The most studied form of TRF is Ramadan fasting, which involves approximately 1 month of complete fasting (both food and fluid) from sunrise to sunset. Unsurprisingly, significant weight loss occurs, and this includes a reduction in lean mass as well as fat mass (11-12). 

Aside from Ramadan fasting studies, there’s a scarcity of human TRF research in the peer-reviewed literature. Stote et al (13) compared 1 versus 3 meals per day in eucaloric (weight–maintenance) conditions for 8 weeks and surprisingly found 1 meal resulted in fat loss and lean mass gain, while no significant improvements were detected in the 3-meal group. Unfortunately, the use of bioelectrical impedance (BIA) keeps these results questionable. Perhaps the only other longitudinal TRF study was done back in 1971 by Young et al, (14) who found no significant differences in weight loss and body composition change between 1, 3, or 6 meals per day

As for TRF programs in the lay press, Hofmekler’s Warrior Diet (15) published in 2002, was perhaps the first popular diet book to expose the general audience to TRF for weight loss. It involves a 4-6 hour feeding period at night, and an 18-hour “under-feeding” period during the day. The diet draws inspiration and justification from the purported habits of our Stone Age ancestors, as well as other leaps of faith involving the sympathetic and autonomic nervous systems. 

Berkhan’s Leangains system of TRF has a 16-hour ‘fasting’ period and an 8 hour feeding period (16). What separates this protocol from others is its attention to macronutrition, and its administration of branched chain amino acids (BCAAs) during the fasting period. As a matter of trivia that you might enjoy, Hofmekler and Berkhan’s were recently referenced in the peer-reviewed literature (17).
MB: Let me translate that. What Alan means to say is that Hofmekler's Warrior Diet is full of pseudoscientific nonsense and I agree wholeheartedly. 

Article continues...

The most comprehensive systematic review on IF to-date

Seimon et al (18) recently published the largest systematic review of IF research to-date. Importantly, they compared the effects of intermittent energy restriction (IER) to continuous energy restriction (CER) on bodyweight, body composition, and other clinical parameters. Their review included 40 studies in total, 12 of which directly compared an IER with a CER condition.

They found that overall, the two diet types resulted in “apparently equivalent outcomes” in terms of bodyweight reduction and body composition change. In addition, neither IER or CER was superior to the other at improving glucose control/insulin sensitivity. No different effects on thyroid, cortisol, and sex hormones were seen between IER and CER, though the authors concede that there’s insufficient research comparing neuroendocrine effects of the two diet types to draw definitive conclusions in this area.

Interestingly, IER was superior at suppressing hunger. The authors speculated that this might be attributable to ketone production in the fasting phases. However, this effect was somewhat immaterial since it failed to translate into superior improvements in body composition or greater weight loss.

MB: Well, that's not quite true. These studies didn't have a suitable control group, as the participants served as their own controls. Thus, you can't say that it didn't translate into "superior improvements in body composition or greater weight loss" - it might have done so for that that group, even if that conclusion can't be drawn from the collected brunt of data. That's the problem with these systematic reviews Like it says in the paper:

Only 12 of the 40 publications included in this review directly compared IER with CER: the lack of direct comparison makes it difficult to determine whether IER is superior to CER, or for whom.

- Seimon, et al. (2015)



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Limitations of the review included the standard ones – relatively small sample sizes, relatively short trial durations, and heterogeneous study designs making comparisons outside of the same study difficult. An acknowledged limitation worth highlighting was that 14 of the 40 studies were by the same research group (Varady et al, University of Illinois at Chicago). Ideally, a more diversified and less concentrated set of labs is less likely to repeat the same errors or preserve the same biases.

Speaking of the potential for bias, Varady has published a lay- directed book titled, The Every-Other-Day Diet (19). I’m not claiming that Varady is destined to make sure her ADF study results will always square up with her book, but it’s one of the potential caveats nevertheless. I would add to these limitations that there’s a severe lack of IER (and IER vs CER) studies that include a structured training component.

Of the 152 industry-funded studies she has examined, 140 boast results that favor the funder. That's more than 90 percent.

- Food companies distort nutrition science. Here's how to stop them.


If you want to read more about this topic as it pertains to nutritional science, check out Marion Nestle and her writings. She's quite brilliant.





Why Calories Count by Marion Nestle. I found this book in a large box of bullshit that I ordered from Amazon two years ago. It was the only thing worth scavenging and I intend to read it after I'm done with a few horror novels. I figure that I'd be properly warmed up by then. A book about food politics and marketing shenanigans can get quite dark and depressing no doubt.


But food companies are as unlikely to fund research on intermittent fasting, as Coca Cola is unlikely to fund research on ketogenic diets. What Alan brings up is the potential for bias on the researcher's part, Krista Varady to be specific. Aside from researching intermittent fasting, she is also involved in selling books, namely books based off of the research she is doing. What gives?

Well. While I haven't read The Every-Other-Day Diet, but I have mixed feelings about Krista Varady. She does try a bit too hard for my liking. I covered her work* before in "Intermittent Fasting For Weight Loss Preserves Muscle Mass?" back in the days and found several problems. Note that I'm wrongfully referring to Varady as "he" in that article. In short, she published a pretty shitty review of the subject, but then again, there weren't that many data points around in 2011. Five years later, it's gotten a little better, but there's still not enough good data around to draw any definitive conclusions - and like Alan says, a lot of that data comes from the same lab (Varady's).

It's worth mentioning that Varady appeared in a laughable infomercial documentary called "Eat, Fast and Live Longer" on BBC Horizon. In it, Michael Mosley - the show host and soon-to-be-author, interviews researchers working in the field of intermittent fasting and Varady is one of them. After rewatching the segment she appeared in, I found her to be matter of fact and professional even though she dutifully suffered through all the TV show gimmicks thrown at her - they gorged on hamburgers and fries to show that you could stuff your face and still lose weight on ADF, for example.

By the way, this "documentary" served as a launching pad for Michael Mosley's worthless book The FastDiet. Seems like there was some kind of falling out between Varady and Mosley after that. Anyway. Don't waste your money. If you want a book on intermittent fasting, pick up Eat Stop Eat.

Now, speaking of Varady, there's nothing wrong with pushing your agenda, but don't shove it down peoples throats by publishing bad research and doing shady shit like failing to disclose your conflicts of interest, because that makes you suspect in my eyes.

That said, there's nothing fishy about her recent work, as far as I can tell. It's entirely possible that Varady and her colleagues got together one night and decided amongst themselves to doctor the results, but I find that very unlikely.





It's kind of spooky, but a client just sent me this two minutes ago. I'm mentioned on the same page as Mosley and Varady, and I'm reading it just as I finish up this paragraph. I believe he was reading a book by his doctor, Robin Willcourt. I'll have to ask about the title, so I'll add it here later for those interested. Update: Name of the book is  Chasing Antelopes: Why All This Caused All That


When fuckery strikes in science, it's usually a lot more subtle and sinister. I would know, because years ago, I approached Alan with this subject. See, I had uncovered some sophisticated tampering with the results of a study that received a lot of spin on social media and the mainstream news. I was slightly distressed over the fact that he had missed it - the studies appeared in the AARR, not only once, but twice - and presented my findings. I needed a second opinion, because maybe I was making a hen out of a feather.

Nope. Alan agreed, it was some shady shit. In fact, it was a case study in deceit. Career-ending, if you ask me. But to this day, no one has debunked the findings, and the researcher is still active; polluting the journals with more bullshit for every new study that gets published. Who knows, maybe one day I'll put an end to it.

The key point of all this, is that science can't be trusted for shit, unless you do your due diligence and read the fine print. But in this particular case, concerning Krista Varady, I'm not worried.


Article continues below...


This limitation also plagues the body of research comparing various within-day meal frequencies. Readers familiar with my work know that Brad Schoenfeld, James Krieger, and I did a meta-analysis on the effect of meal frequency on body composition, and found that higher meal frequencies were associated with greater losses of fat mass and greater retention of lean mass (20). However, sensitivity analysis revealed that the removal of a single study (21) completely eliminated the significant effect of meal frequency on changes in body composition.

It’s worth noting that the studies in our analysis (and in this entire body of literature) lacked sufficient protein. An exception was Arciero et al (22) who found that 6 meals per day at 35% of total kcal as protein was superior to 3 meals per day for reducing total body fat and abdominal fat. Furthermore, 6 meals per day increased lean mass despite hypocaloric conditions.


MB: Sure thing. Something like that only happens in a study sponsored by EAS, Alan.
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What about muscle gain? 

The retention of lean mass in IF studies has been seen repeatedly. However, the question of muscle gain via IF remains unanswered since the investigative focus of IF research has been on weight/fat loss and accompanying clinical effects. No IF studies in the current literature have focused on the goal of gains in muscle size and/or strength. As such, No IF studies to-date (at least none that have passed peer review) have included a structured, progressive resistance training program.

This is untreaded ground fresh for the taking by researchers with the desire to do so. With that said, a poster presentation by Tinsley et al (23) at the The 12th ISSN Conference and Expo provided a summary of their study that compared the effects of TRF (on non-training days, all calories consumed in a 4-hour period) and progressive esistance training (RT) 3 days a week for 8 weeks – versus an RT group presumably on their usual diet. No between-group differences were seen in body composition, but interestingly, TRT+RT outperformed the RT in leg press maximal strength and in bench press endurance. The full text of this will be interesting to dig into if/when this study makes it into publication.

The Editor’s Cut of the May 2012 issue of AARR pondered the question of what might be the lower threshold of meal frequency for optimizing muscle gain. I concluded that this threshold, based on what we knew at the time, was probably 3 protein-rich meals. I contended that a lower daily meal frequency than that would compromise maximal rates of muscle gain. Since that time, a replication of well-controlled studies has shown the superiority of 4 doses of 20 g whey eliciting a stronger anabolic response during a 12-hour period than 2 doses of 40 g or 8 doses of 10 g (24, 25). These findings made me re-think my position of a 3- meal minimum. It’s plausible that folks with the goal of maximizing rates of muscle gain should look to a minimum of 4 daily doses of protein at of at least 20-40 g (older subjects require 35-40 g to maximize the anabolic response). (26-28)



MB: This is all nice and dandy in theory, if it weren't for the fact that...

1. The studies that made Alan "re-think" his position of a 3-meal minimum are all funded by Néstle - a controversial company who likes to be addressed as the “world’s leading nutrition, health and wellness company.” The former Néstle-owned supplement company Musashi supplied the whey protein used in at least one of the two studies Alan cites.

Remember the quote from Marion Nestle - no relation to the company Nestlé - earlier in the article? Here it is again:

Of the 152 industry-funded studies she has examined, 140 boast results that favor the funder. That's more than 90 percent.

If you think the supplement industry is any different, you're batshit crazy. I'm willing to go out on a limb and say that it's closer to a 100% when it comes to the supplement industry.


2. The results obtained in these studies are unlikely to be relevant for real-world eating habits and real-world results.

However, it is important to note that this response was characterised when protein was ingested alone, and as the authors acknowledge, this finding cannot be evaluated in the context of a mixed meal. Indeed, it is commonplace to consume protein in the form of a mixed-macronutrient meal. Therefore, it is reasonable to postulate that macronutrient co-ingestion could alter intestinal transit, thus influencing amino acid absorption kinetics (Deutz et al. 1995) and perhaps MPS. Moreover, this study used high-quality whey protein

Of course, the big limitation is that acute studies can measure protein synthesis but they can’t measure changes in body composition. Recent work by MacKenzie-Shalders found no significant difference in lean mass increase between a high protein intake (2.6-2.7 g/kg) spread across 4 vs 6 meals in elite rugby players. This findings are interesting, but once again, 3 meals per day remains a gray area in the question of a minimum for maximizing muscle growth. Perhaps future studies will compare 3 meals versus 5 or 6 for this purpose – while imposing an energy surplus and a progressive resistance training program. Seems like just a matter of time before someone in the current or newer generation of researchers attacks this gap in the literature.

Concluding perspectives & applications 

IF has proven itself to be an effective approach to dieting, and has outperformed conventional dieting in some cases. In the interest of cohesion to the topic, this article didn’t delve into IF’s effect on athletic performance. However, it’s important to keep in mind that IF protocols can compromise performance goals if careful modifications are not made. In general, IF is best applied to goals oriented toward altering body composition and clinical markers that occur alongside body fat reduction. This is not to say that muscle gain cannot occur with IF – it’s just that the rates of gain will not likely be maximised.

As for which IF variant to chose (ADF, WDF, TRF, etc) if one decides to try IF, the good news is that they all have demonstrated effectiveness in the literature, and therefore can be chosen on the basis of personal preference. Just remember that there is no special metabolic magic in IF, just like there’s no stoking the metabolic furnace with 6 meals a day.


Article ends.