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Burning the Calories Before Refueling? Should we be Exercising in a Fasted State?

roadskater's picture

We've talked about the idea of bonk training before, and I don't claim to know a lot, but know I have done it. Often it was not "breakfast" time, but for various reasons it was still over 6 to 8 hours, sometimes more, since the previous meal. This might have been due to odd work hour schedules or preoccupation with all sorts of things, but sometimes I showed up at the park to skate in a fasted state. 

It does not make for a great workout where you feel all wonderful and get the dolphins swimming in your blood (endorphins), and it is supposedly better for people who are not the most fit (but are fit enough of course). Anyway, here's some more on the subject, from relatively reliable sources...

The experiment lasted for six weeks. At the end, the nonexercising group was, to no one’s surprise, super-sized, having packed on an average of more than six pounds. They had also developed insulin resistance — their muscles were no longer responding well to insulin and weren’t pulling sugar (or, more technically, glucose) out of the bloodstream efficiently — and they had begun storing extra fat within and between their muscle cells. Both insulin resistance and fat-marbled muscles are metabolically unhealthy conditions that can be precursors of diabetes.

* * *

Only the group that exercised before breakfast gained almost no weight and showed no signs of insulin resistance. They also burned the fat they were taking in more efficiently. “Our current data,” the study’s authors wrote, “indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state to stimulate glucose tolerance despite a hypercaloric high-fat diet.”


There's more to it, so check out the article. This was just a note to put this into my mind and into our conversation. 


eebee's picture

That's an intriguing claim.

“...indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state to stimulate glucose tolerance despite a hypercaloric high-fat diet.”

This would suggest I could eat pizza and chocolate all day long and not gain weight as long as I hauled my butt out of bed every morning and went to skate for an hour in a state of fast. In reality though I'd probably feel absolutely exhausted from trying to digest all that fat and would not be able to get up out of bed at all. 

This made me laugh:

"...researchers in Belgium recruited 28 healthy, active young men and began stuffing them with a truly lousy diet..."

So they followed a bunch of freshman college kids around :-)

Seriously though, I'd like to read the details of this study, specifically what exactly the carb-loading group had been fed for breakfast and more importantly, when:

"One of the groups ate a hefty, carbohydrate-rich breakfast before exercising and continued to ingest carbohydrates, in the form of something like a sports drink, throughout their workouts..". 

And by the end of the study they too had gained weight and

"... had become more insulin-resistant and were storing a greater amount of fat in their muscles."

Makes sense to me, if they were chugging corn syrup during a 60 - 90 minute workout. Yuck!

I am sold on Joe Friel's Paleo Diet for Athletes - in thought if not in deed. Friel explains in the book that a serious long-distance athlete attempting to follow a paleo-type diet needs to begin carb loading with decidedly non-caveman food 4-5 hours before a race or training session. I don't have the book with me for reference but I've read this part about ten times now and it's  finally starting to sink in. This means getting up at 4 am, and for the next four hours figuring out how to down 900 calories worth of a low- to high-glycemic carb mix. And you shouldn't eat anything at all during the hour immediately preceding your start time - save for an energy gel ten minutes max before kick off. So those start line bagels, cream cheese and chicken biscuits are probably the worst things you could eat unless you want to pull over half a mile into it and take a nap.  

Friel and co-author Loren Cordain put a lot of research and effort into this method, with Friel test-driving it himself, so I'm inclined to believe that this approach is effective. So in that sense, I'm not surprised those poor Belgian dudes' bodies reacted poorly.  I can't find the details in what they were fed and when before the morning workout, but I imagine they didn't start carb-loading at 4am. 

Some of the reader-comments posted for that NY Times article ask if a study of strapping young men is of any use to middle-aged women. Not that anybody ever promised it would be. But really, any exercise is better than nothing, and middle-aged women can start putting general exercise lore into practice, and tweak it till it works for them. There is enough fitness and sports info out there to keep you busy for years. Sometimes it's easier to sit around and complain, though. 

roadskater's picture

Abstract for the Fasted State Exercising Study

This link seems to work if you go to the article above in the New York Times and click there. Sorry. Here's the link for historical purposes...


You might try this one as an alternate...


eebee's picture

50% fat diet

I almost spat out my bacon and eggs in disgust when I read that the 'unhealthy' group was fed a 50% fat diet with a 30% increase in overall calories (than the other groups, I presume). Then I realized how easy it is to rack up a diet consisting of 50% fat calories. When I'm not paying attention, I probably manage 75%, easily.

timv's picture

Farmer's breakfast

The thing is that I've had some great skating and bike riding experiences when my schedule was such that I could have a couple of greasy ham & egg sandwiches or breakfast burritos at 4 AM or so. It really kicks in around midmorning when everyone else is starting to go flat.

If I'd grown up in a household where breakfasts like this were the norm, maybe I'd even have turned out to be a morning person.

MikeB's picture


Seems like such things are dictated individually by trial and error (mostly error).  Personally, starting to load up 48 hrs before an event has worked really well (carbs + electrolytes, etc.).  Combine this with good rest the night before and a small but sensible breakfast has the muscles at their most ready and the stomach not too full.

Working out in a fasted state makes me quit...........fast.

timv's picture

Catching up

Agreed. I was trying to follow exercise physiology more closely a decade or so, not so much in recent years, but my feeling hasn't changed that scholarship is still moslty trying to catch up with what coaches and athletes have figured out through day-by-day and event-by-event experimentation--to explain why what's known to work actually works.

Working out in a fasted state makes me quit...........fast.

Yeah, is any of this going to take me from, say, 50% percentile to 60% percentile in event results, and if it did would it be worth the aggravation when this is all done for fun anyway? Because I know that just getting out and doing decent mileage on a regular basis will do at least that much for me if I can just do that, and that's mainly about enjoying it while I'm doing it.

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