Sauron is a huge "Mythbusters" fan. Trufax.
It’s one of those statements that folks at your local fitness haven put out there that, on the face of it, looks like it might just be plausible: “If you work out, your body keeps burning more energy for up to (select one): twelve / twenty-four / thirty-six hours afterward.”
Which, for certain values of “work out,” appears to be true. It’s that certain values bit that gives lie to the general proscription. While there is definitely evidence of elevated caloric consumption immediately after exercise, a recent study seems to throw a measure of, er, cold water on those metabolic fires. It’s not all bad news, but it isn’t quite as TAANSTAFL as some folks might have thought.
In a nutshell, the research surrounding post-exercise fat burning indicates that there are two things that really contribute the long-term reduction of our fat stores: intensity and nutrition.
[The study findings are] ”dispelling the myth that you can create a 24-hour fat-burning situation after exercise. These results [from moderate-intensity exercise lasting less than an hour] might not apply to different forms of exercise or higher-intensity exercise.”
- Pete McCall, exercise physiologist and spokesman for the American Council on Exercise
First, the extended afterburn from exercise only happens when you really bust your butt. Well, I’m gonna be the last person to try to dissuade anyone from doing that (assuming you’re up to it, and not hurting yourself — safe, sane and consensual isn’t just for the boudoir, people). Light to moderate exercise doesn’t get things cranked up enough to keep that particular ball rolling for a long while afterwards. This certainly passes the common sense sniff test: elevating one’s metabolism less makes it easier to come back down.
Secondly, and this is a bit subtler, is the contribution that pre-, peri-, and post-workout nutrition play as far as fat-burning, as well as general overall health and wellness. The short form is, simple carbohydrates cause your body to do two things that work against burning fat: cause your body to produce excess insulin (which works to store sugars for energy) — the so-called “insulin spike” — and simply use those carbs for energy, instead of burning fat.
Why don’t we become long-term fat burners after a good workout? The most likely reason is that we eat. And what we eat affects fat burning.
Participants [in Melanson's study] were fed a diet that was 20% fat, 65% carbs, and 15% protein for three days before each [exercise] session, and on the day they exercised or did not exercise
For instance, eating as little as 240 calories of carbohydrates during the hour before exercise can reduce fat burning during exercise, and the boost in fat burning during exercise can be “blunted” for up to six hours after eating a meal, says Dr. Edward Melanson (associate professor of medicine at the University of Colorado), citing other research.
- Kathleen Doheny, WebMD
Unlike conscious eating decisions, like choosing what we want to grab out of the fridge or pick from a menu, our bodies will always take the path of least resistance when it comes to looking for energy sources. Simple carbohydrates (sugars) will be burned first, then complex carbohydrates (whole grains). Only when these aren’t available will our body finally look around and say, “Well, I guess I better start cutting into my fat savings, or begin nibbling on muscle (protein)” just like it’s easier to spend money in your wallet than go digging under the couch cushions or busting open that decorative piggy bank.
From an evolutionary standpoint, this makes perfect sense — fat is incredibly efficient at storing calories, and when food supplies are uncertain, stockpiling reserve calories against a (literally) rainy day was a survival adaptation. Had there been Kwik-E-Marts on the savannah half a million years ago, well, they’d really need painting.
So, what can we do to maximize the fat-reduction benefits of our fitness time? If you can work a little bit harder, by all means, do so. If you’re already there, take a look at what you’re taking in before, during, or after your workout — and reach for something lower-carb and higher-protein if you can.
Those vaguely dippy EAS commercials, where some athlete or other says their workout isn’t over until they’ve had their protein shake? That’s actually good nutritional science, not mere marketing foolishness.
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Makes the whole low-carb thing make sense. Only give it two fuels to burn up instead of four (using the fuels from the article as reference). Goes right for burning the fat…but will eventually fall back into burning off a bit of muscle as well and do a number of other bad things in the long run.
If I’m reading this right, it also seem to make a case for working out first thing in morning?
There are some folks who suggest that that’s the best time to work out to burn a little extra. That, combined with the not-bullshit notion that Breakfast Is Really Important might point folks towards doing an early-morning workout, followed by a protein shake to start the day.
For my part, I’ve usually got about fifteen minutes between when I stop smacking the snooze alarm and when I have to throw myself into the morning commute, so this sort of schedule just doesn’t work for me.
For those folks who habitually get up early, or can go into work a little later? Give it a shot.