As the evidence for intermittent fasting (“time restricted feeding”) continues to become more and more robust, the discussion is shifting from “Is the purported effect real?” to “Who are the populations who can best put this to use?”.
Some of the early adopters (recently, not historically) were certain athletes tired of counting every morsel of food all of the time. The research community has further added the life extension benefits as a result of experiments done on other mammals.
The paradox is that, as we age, lean mass becomes more and more important and valuable. Beyond mere vanity, lean tissue is our primary shock absorber, modulates our endocrine system, maintains glucose homeostasis, and minimizes aches and pains associated with aging. None of that mentions the physiological benefits I’ve discussed in talks over the past 6 years!
I’m nearly 35, so I still want as much lean mass as possible while also aiming to reduce the physiological state that might be conducive to tumor growth, given my family history of cancer. This means managing IGF-1, insulin sensitivity, and inflammation.
The Best of Both Worlds?
I’ve been doing some form of intermittent fasting since ~2007, largely on basic science arguments from the likes of Martin Berkhan and Brad Pilon. Later, I became aware of the work of Krista Varidy and Valter Longo, who had decidedly different aims but enhanced the literature.
Specifically, Longo’s aim was to improve longevity and health span by modulating IGF-1, inflammation, and other understood mechanisms for growth. His solution was a 25:5 structure where you eat ad libitum for 25 days and then go on a low calorie, low protein, low carbohydrate diet, high fat for 5 days before returning to normal eating habits. For the intended goal, the result is impressive. Markers associated with aging, cancer, and diabetes did indeed plummet, as did a modest amount of body fat.
However, to quote Lyle McDonald, getting into a healthy body fat range is all about psychology. These individuals were going to lose fat on the 25:5 diet because they weren’t super lean to begin with, as everyone was north of 25 on the BMI scale. Going below ~15% is all about physiology and you’ll sacrifice lean mass if you eliminate all protein.
A study of a “lean gains” style intermittent fasting demonstrated something curious. These individuals were well trained (an average bench of ~220lbs for example) and not small. However, in addition to gaining muscle and strength consuming a eucaloric diet, their IGF-1 and inflammation markers dropped substantially. Again, not a “low calorie” or “fasting mimicking” diet, just calories shifted around.
I’ve said in the past that calories are the universally permissive variable. You can piss ketones on an all potato diet *IF* you’re only consuming 700 calories. There is data on obese youth consuming protein-sparing modified fast (PSMF) that shows reductions in IGF-1, unfortunately I cannot find anything for adults that isn’t tube fed. Given that, and based on the lean gains study above, if you time-restrict the feeding I suspect that you can both maintain lean mass AND get the anti-everything benefits of the fasting mimicking diet while consuming a highish-protein PSMF.
So a 5 day plan might look like this:
- Day 1: Resistance training, 1.5-2.0 grams of protein per pound of lean body mass
- Day 2-5: Walking or low intensity cardio, 1.0 to 1.25 grams of protein per pound of lean body mass
- Day 6: Refeed with “safe starches” (1.5 – 2.0 grams per pound of lean mass) and lean protein
- Day 7: Return to high quality eating habits, with at least a 16:8 fasting/feeding window
Add to that mineral water and multi vitamin and you’re good to go.
Skyler Tanner 
Interesting post. Some thoughts….
I tried intermittent fasting of the 16:8 variety, for about 3 months. I had lots of fat to lose. I did drop maybe 3-4 lbs initially, and then nothing. Perhaps it works for some people as a weight loss strategy, but there are others for whom ad libitum eating outside the fasting period will overwhelm everything else. Regarding Longo’s protocol: I can’t speak to the cellular level metabolic effects, but for someone with a pleasure eating problem, a 5 day stretch of low calorie ketogenic dieting which subsequently permits ad libitum eating for 25 days doesn’t seem likely to produce a net reduction in calories.
Regarding cancer: it seems that certain kinds of diets or eating patterns can, in the the short run, slow the growth of a tumor. However, it is an extrapolation to go from that kind of intervention with an already ill person to the conclusion that such strategies will prevent cancer. I saw a recent study which suggested that 2/3rds of all cancers are the result of random mutations. How much will intermittent fasting, or ketogenic fasts, impact that roll of the dice?
Finally: You seem to be suggest that reducing body fat below 15% (for a male) will likely mean sacrificing lean muscle mass, which is generally not a good thing. Is that a correct interpretation? I’ve had my suspicions for a while that getting really ripped (as in Clarence Bass lean) might be mostly for aesthetics, with no real upside in terms of health.
Craig, I’m going to do a response blog post because these are great questions!
Skyler
It is always interesting and helpful to read your thoughts and experiences.
I’ve also been observing the interest in intermittent fasting over the last 12 year or so. It has been fascinating to watch it go from a situation where you had Brad Pilon selling his book – which was excellent- then Martin B with the more complicated Leangains (calorie and macro cycling plus his 16/8 window) honed by all his debates with Lyle and others, then seeing it popularised in the internet bubble by Greg o’Gallagher and Andy Morgan. Finally hitting the mainstream with the 5:2 diet stuff.
I’ve used it as a tool over the years – the odd 24 hour fast and often a compressed eating window. What has sparked my interest recently has been Rhonda Patrick’s interviews with Dr Satchin Panda on his work on Time Restricted Feeding. This is not from a “bodybulding” perspective as such but around general health. What that has changed for me is the idea of trying to match eating with circadian rhythms – eating in the day, fasting overnight. The bro approach of breakfast skipping is pretty much the opposite to this.
Then of course there is Art Devany – he has been promoting his intermittent fasting for years and seems to have re-emerged on the internet in recent months via Facebook and various podcasts.
Anyway – good to see you writing again
Chris
Chris,
Thanks for the kind words and thoughts.
Two things:
1. I’m skeptical (to put it lightly) of the conclusions that are drawn from animal models with regard IF, especially the notion that food and drink are the most important thing in this regard. I even wrote about it here:
https://skylertanner.com/2017/02/15/on-time-restricted-feeding/
2. Part of the reason I reference Longo and the “Leangains” study is because they’re on Humans over time. It’s not a silly mouse model being extrapolated, nor is it a single data point on humans being extrapolated (“afternoon diabetes” as Lagakos puts it). That and natural experiments mentioned above are much more compelling IMO.
Thanks Skyler – sorry I had missed your 15 February post where you address all of this… apologies
No worries! Thanks!