Wednesday, March 10, 2010

Calories In, Calories Out

I’m guessing that -- like me -- lots of folks got into P90X, Insanity, Turbulence Training, or other exercise program as a way to drop a few pounds and “tone up” a bit. But in the excitement of starting a new, challenging workout routine, we sometimes forget that diet's actually more important than exercise when battling the bulge.

It's a myth that working out is the key to losing weight. As I’ve mentioned before, the scientific consensus is that exercise alone doesn’t drive significant weight loss, but this message just isn't getting through. On shows like “The Biggest Loser,” overweight contestants are shown getting their asses handed to them by trainers who march them through up to six hours of exercise per day -- all in the name of surviving a humiliating “weigh-in” process at the end of the week. Yes, some onscreen time is devoted to doling out nutrition tips, but the grueling workouts remain the primary focus of the program. (I have to admit, though, that gawking at people who exercise to the point of vomiting is much more visually arresting than a watching a guy put three ounces of chicken on a kitchen scale while droning on about portion control).

But even outside of reality TV, there's a widespread assumption that exercise produces a post-workout “afterburn” that torches calories well after you've changed out of your gym clothes. As the New York Times points out:
“Many people believe that you rev up” your metabolism after an exercise session “so that you burn additional body fat throughout the day,” said Edward Melanson, Ph.D., an associate professor in the division of endocrinology at the [University of Colorado] School of Medicine ... If afterburn were found to exist, it would suggest that even if you replaced the calories you used during an exercise session, you should lose weight, without gaining weight — the proverbial free lunch.
But after conducting a study among athletes and non-athletes, University of Colorado researchers "found that none of the groups, including the athletes, experienced ‘afterburn.’ They did not use additional body fat on the day when they exercised. In fact, most of the subjects burned slightly less fat over the 24-hour study period when they exercised than when they did not."

The problem, it seems, is that vigorous exercise makes us want to eat more.
"In general, for weight loss, exercise is pretty useless," says Eric Ravussin, chair in diabetes and metabolism at Louisiana State University and a prominent exercise researcher. Many recent studies have found that exercise isn't as important in helping people lose weight as you hear so regularly in gym advertisements or on shows like The Biggest Loser ...

The basic problem is that while it's true that exercise burns calories and that you must burn calories to lose weight, exercise has another effect: it can stimulate hunger. That causes us to eat more, which in turn can negate the weight-loss benefits we just accrued. Exercise, in other words, isn't necessarily helping us lose weight. It may even be making it harder.
Plus, people tend to overestimate the calories they’ve burned, while underestimating the calories they ingest to sate their workout-induced hunger. The electronic calorie counters on fitness machines don’t help; in fact, many of them (especially the ones on elliptical machines) wildly overestimate users' calorie-burn.
In other words, while you may think you just torched 500 calories after a hardcore session on the elliptical (and that you're going to benefit from a post-workout afterburn, too), your actual output may be closer to 300 calories. And now, you're famished, but if you wash down a banana and a PowerBar with a bottle of Gatorade, you'll have consumed 460 calories.
[T]here's the rub: Few people appreciate the amount of activity required to compensate for even small amounts of food. To lose 500 calories through exercise would require a daily eight-kilometre walk or run, or an hour of vigorous exercise.

"It's always disheartening to be on the treadmill and be sweating and sweating and sweating, and you realize, this is just 200 calories? It's not even a candy bar," says Amy Luke, an associate professor in the department of preventive medicine and epidemiology at Loyola University Chicago Stritch School of Medicine.

People can overcompensate for the calories burned during a typical workout before even leaving the gym. The Dairy Farmers of Canada recently began promoting low-fat chocolate milk as a post-exercise recovery drink, based on studies suggesting that the protein found in chocolate milk helps recharge muscles.

One 500 ml carton of 1% chocolate milk contains 332 calories.

"For the vast majority of gym-goers that would be about an hour's worth of exercise," says Dr. Yoni Freedhoff, an Ottawa doctor who runs an obesity treatment clinic. "So, at best, you're breaking even. At worst, you come out behind."

One of Mark Sisson’s mantras is that “80% of your body composition will be determined by your diet. Yes, exercise is also important to health and to speed up fat-burning and muscle-building, but most of your results will come from how you eat.”
I believe it. Towards the end of Round 2 (which -- as you’ll recall -- involved frequent Insanity sessions), I found myself taking in a lot more food after my workouts. In particular, I was loading up on carbs. I guess this shouldn't have come as a surprise; after all, calorie compensation “can be triggered by particularly intense workouts,” and we're conditioned to crave carbs when we're hungry.
[T]he desire to compensate is … physiological, says Church. "No doubt the body wants to replenish," particularly after a grueling exercise routine.

The widespread availability of calorie-dense, carbohydrate-heavy foods complicates the problem, says Leslie Bonci, director of sports nutrition at the University of Pittsburgh Medical Center. Many people crave carbohydrates after a workout but, to a degree, that "taste" has been engineered by the marketing of energy bars and drinks packed with sugar, she says. "We've been conditioned, like Pavlov's dogs," says Bonci. "I don't know anyone who really craves a salad after working out."
So after a tough Round 2 session of Max Cardio Conditioning or whatever, I'd often reach for some lavash crackers and slather 'em with peanut butter. I'd eat them along with a banana. And maybe a cheese omelet -- sometimes with toast. And a big handful of nuts. And possibly a protein shake. In my hungry, exercise-addled mind, I'd burned so many calories during my workout that it didn't matter what I decided to eat afterwards.

I was wrong. I put on almost five pounds between the end of Round 1 and Round 2 -- despite doing crazy-intense interval training with Insanity.

With Round 3, I’ve renewed my focus on what I’m eating. No, I’m not counting calories (unlike M, who now has a BodyBugg and is logging all her food into the BodyBugg website with an almost religious zeal), and I'm certainly not depriving myself, but I’ve stopped eating mindlessly after my workouts. In fact, just cutting back my intake of carb-y, calorie-rich grains has made a huge difference; in less than three weeks, I’ve returned to my pre-Round 2 weight -- and I’m no longer hobbling around from too-frequent high-impact Insanity sessions, either.

I’m rambling now, so I’ll stop. But in case you missed it, here's the moral of the story: Exercise is awesome, but if you’re looking to lose weight or stay trim, don’t lose sight of the importance of diet and nutrition.

Still want more info? Check out this post by Nerd Fitness on "How to Lose Weight Without Doing One Minute of Exercise."