Meal & exercise timing in the contexts of “damage control” and nutrient partitioning are frequent topics on this blog. I generally opt for a pre-workout meal, but nutrient timing hasn’t panned out very well in the literature. That’s probably why I’m open to the idea of resistance exercise in the fasted state. A lot of pseudoscientific arguments can be made for both fed and fasted exercise, and since a few blog posts have already been dedicated to the former, this one will focus on the latter.
The pseudoscience explanation is something like this: since fatty acids are elevated when fasting, exercise in this condition will burn more fat; and chronically doing so will increase mitochondria #. The lack of dietary carbs might enhance exercise-induced glycogen depletion, which itself would bias more post-workout calories toward glycogen synthesis / supercompensation. Much of this is actually true, but has really only been validated for endurance training (eg, Stannard 2010, Van Proeyen 2011, & Trabelsi 2012; but not here Paoli 2011)… and the few times it’s been studied in the context of resistance exercise, no effect (eg, Moore 2007 & Trabelsi 2013). However, there are some pretty interesting tidbits (beyond the pseudoscience) which suggest how/why it might work, in the right context.
John Kiefer, an advocate of resistance exercise in the fasted state, mentioned: “the sympathetic nervous system responds quicker to fasted-exercise. You release adrenaline faster. Your body is more sensitive particularly to the fat burning properties of adrenaline and you get bigger rushes of adrenaline.”
Much of this is spot on. That is, ketogenic dieting and glycogen depletion increase exercise-induced sympathetic activation and fat oxidation (eg, Jansson 1982, Langfort 1996, & Weltan 1998).
The question is: can this improve nutrient partitioning and physical performance? Magic 8-Ball says: “Signs point to yes.” I concur.
Contrary to popular beliefs, glycogen depletion per se doesn’t harm many aspects of physical performance. A lot of fuel systems are at play; you don’t need a full tank of glycogen.
Increased fat oxidation compensates for reduced glycogen at lower exercise intensities (eg, Zderic 2004), and ketoadaptation may do the same at higher intensities.
(which may or may not be acting through SIRT1; this is controversial). While alcohol does no great favors for circadian biology, if you’re going to imbibe, perhaps a resveratrol-rich Argentinian malbec served, and this might be the important part, at night, when all of this stuff is going on… coincidentally [fortunately], that’s precisely when most choose to imbibe.
(1.2 g/kg ideal body weight from lean meat, fish, or fowl; probably around 80 grams of protein/d, 500-750 kcal/d). They lost a lot of weight, 23 pounds on average, two-thirds of which was body fat. There was no exercise intervention, just the performance assessments.
as indicated by lower RQ at every level of exercise intensity:
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: 45-50% carbs; 45 grams per meal + three 15 gram snacks = 165 grams per day; low fat, calorie restricted (500 Calorie deficit). Otherwise known as a “low fat diet (LFD).”
: Ketogenic; <50 grams of carb per day, no calorie restriction, just a goal of blood ketones 0.5 – 3 mM.