Hi to all
Having read some of the debate on this forum, and several similar ones elsewhere on the net, I thought I'd post some of my experience as a long-term practitioner of something approximating IF. I also train regularly, not with heavy weights, but with Len Schwartz's Heavyhands methods for the last 20+ years, and am generally active with hiking, biking and skiing. My primary goals are to be active, energetic and healthy, and at 57 I feel I'm pretty much achieving this. I have my eye on Len Schwartz himself as a model, and at 82 he's still going strong, and continues to research and practice a variety of new training methods. Myself, at 5' 10", I'm usually around 163lbs, with a resting heart rate of 40, and (Tanita assessed) bodyfat of about 8-9%. I guess in appearance my build is not too dissimilar to Dr Schwartz's as illustrated at the same age - i.e. fairly lean and defined, but without the larger musculature of a heavy weight trainer.
For about the last six years or so I've fasted pretty much daily on about a 20/4 schedule, having transitioned into this gradually and spontaneously from a pattern where I used to eat mainly fruit during the day, and a single fairly wide-ranging meal in the evening. I didn't do this for any particular doctrinaire reason, but rather because though I've never had much appetite before the evening, I also like to eat heartily at least once a day. When I inadvertently gained more than 30 lbs following illness many years back, I used this method, with a somewhat reduced calorie intake in the evenings, to slim down again.
Nowadays I water-fast during the day, occasionally supplemented with tea or black coffee. In the evening, when I have a healthy but not ravenous appetite, I tend to alternate, or juggle, higher carb days (i.e. some potatoes, pasta, rice, or grains) with days when these are replaced with salads. Staples are meat, fowl, fish, nuts, cheese and cooked vegetables, although some days we eat only vegetarian dishes. My training regime is generally 30-45 minutes of outdoor Heavyhands walk or run on rising, with handweights ranging from 3-10 lbs. I do a lot of interval work with short rests, including Tabata protocol, and my training intensities are usually in the 75-90% range (i.e. I sweat quite a lot!) My weekly total would usually be about 3-4 hours, but it has in the past extended to up to 10 hours (when I was chasing calories to drop the extra weight), which then included individual sessions of between 2 and 3 hours. All of these workouts were accomplished without incident or energy problems in the fasting state, and they never left me feeling anything but relaxed and capable of accomplishing the rest of the day's activities before replenishing in the evening.
Recent fairly typical examples of 'fasted exercise' include a week's hiking - when a sample day was scaling a 3200 foot peak after my regular HH morning session - and 6 days alpine skiing. I generally carry some 'emergency' calories with me (fruit or chocolate usually), but it's nearly always my wife who eats them! I should emphasise that I cite these not as an example of anything intended to be an optimum 'formula' for all, but rather as an example of one individual's actual experience over a fairly lengthy period. In general terms of health and well-being, my assumption is that, as well as my subjective assessment, my customary low resting heart rate and BP are indicative of a fairly unstressed basal state, and my relatively high work and recovery capability and high energy levels in the fasted state indicate a good ability to store and recycle nutrients. This would seem to be consistent with the 'thrifty gene' expression hypothesis, in which both 'feast-famine cycles', and exercise are hypothesised to predispose the organism towards glycogen sparing and fatty-acid oxidation during muscular effort (see http://jap.physiology.org/cgi/content/full/96/1/3#SEC5
). In my own case, it hasn't been a personal goal to maximise lean body mass (i.e. 'bulk up'), but my experience has nonetheless been that I've more than maintained it, and greatly improved its work capacity, with my HH and IF-style approach.
Anyway, this is just my experience so far of an 'experiment of one', so I'm certainly not promoting its universal applicability, or indeed claiming that there's anything 'optimal' about it, but it does nevertheless at first encounter strike many as counter-intuitive on a number of fronts. In particular - and this may be at the root of some of the controversies on this topic - my goal has been to find a personally effective way of staying fit, slim, and healthy that would be likely to persist in the long term, because it's consistent with my more deeply rooted inclinations and capacities. For most, this may be more important than how precisely a specific regime matches current notions of what is 'best'. At the same time, since I'm not training for outstanding performance in some competition (except 'life' of course), I'm not so concerned about how to refuel optimally on a daily basis for, say, muscle hypertrophy, or some other pressing athletic goal. So perhaps in the end one size can never fit all.