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.