Wednesday, August 19, 2009

Science Wednesday--Exercise Doesn't Cause Weight Loss? Huh?

It's been drummed into our heads that diet and exercise are necessary to lose weight. Right? Well, Cloud questions this in his controversial article in Time: "Why Exercise Won't Make You Thin". In the article, Cloud questions the efficacy of exercise in weight loss, arguing that because exercise stimulates hunger, people that exercise overeat and end up losing 0 pounds or actually gaining weight.

The conventional wisdom that exercise is essential for shedding pounds is actually fairly new. But the past few years of obesity research show that the role of exercise in weight loss has been wildly overstated.

The article goes on to cite a study where four groups of women were assigned to different durations of exercise per week for 6 months. On average, everyone lost weight (even the control group, who may have lost weight because of becoming self conscious when filling out the health forms); however, the women who exercised the most did not lose the most weight. Unfortunately, the article grossly misinterprets and misrepresents the data. The authors of the study even explicitly state that the experiment was not designed to examine weight loss:

Our findings should not be interpreted as suggesting that lower doses of exercise are more effective in producing weight loss than higher doses. We emphasize that DREW was not a weight loss study and it was not designed to examine the nuances of exercise induced weight loss.

One expert quoted in the Time piece, Dr. Timothy Church, said his professional opinions were misrepresented. Dr. Church declared unequivocally to the LA Times that Time Magazine misunderstood his professional opinion. What he actually believed was that virtually all people who lose weight and keep it off are exercising.

Dr. Martinez from Coastal Sports and Wellness picks apart the Time article and all its errors in detail in his blog response, "Does Reading Time Magazine Make You Dumb?"

The author did a poor job of factual reporting for a junior high school paper, much less a major news magazine...The reality of this exercise study is that the researchers found that all three exercise groups lost weight. Interestingly, the group that exercised the most, did not lose weight at the researchers’ predicted rate – however, that group still lost weight.

Malia Frey from the Minneapolis Fitness Examiner weighs in:

If Cloud mistakenly believed that 30 minutes on the treadmill allows him to sit on the couch all day, eat burgers and malts and still expect to lose weight, that is unfortunate, but I'm not sure that it warrants a cover story in Time magazine.

So does Shari Roan from the LA Times:

However, most research suggests that exercise and dieting are both important for weight loss and that exercise is critical for weight maintenance. It's difficult, but not impossible. Research not cited by the Time article shows that people who have maintained a significant weight loss over a sustained period of time largely rely on exercise to do so. This effort, studies suggest, can eventually retrain the body to respond appropriately to food and activity. Moreover, these people also carefully watch what they eat. In other words, they know that eating a blueberry muffin after their workout will undermine their goals. This evidence was detailed in a 2008 story in the Los Angeles Times' special Health section on weight loss.

Finally, the America College of Sports & Medicine released a statement last week saying it takes "strong exception" to the Time story's conclusions. According to John Jakicic, Ph.D., FACSM (whose own research, published in 2008, showed a high dose of physical activity contributed to the greatest amount of weight loss):

There is strong evidence from the majority of the scientific literature that physical activity is an important component for initial weight loss...The statement ‘in general, for weight loss, exercise is pretty useless’ is not supported by the scientific evidence when there is adherence to a sufficient dose of physical activity in overweight and obese adults. Again, it is clear in this regard that physical activity is one of the most important behavioral factors in enhancing weight loss maintenance and improving long-term weight loss outcomes.

My 2 Cents?
Although I'm sure he has a point in some cases, I am highly skeptical overall. First, exercise makes you healthier. It extends lifespan and prevents a myriad of diseases ranging from cardiovascular disease to Alzheimer's to cancer. Not to mention the antidepressant, mood elevating effects (particularly of vigorous) exercise.

Personally, I have found high volumes of exercise (marathon or Ironman training) disproportionately spike your hunger, which can lead to weight gain if diet is not carefully monitored. But exercise AND diet are both crucial parts of the weight loss equation. In the end, the calories out must be more than calories in to cause the needle on the scale to fall. That's it. Simple as that. So if you calculate what you're burning (exericise) and document what you're eating (diet), subtract--that number should be negative to meet your weight loss goal. I have found that the initial spike in hunger caused by high volumes of exercise dissipates after ~6 months. (Also, intense exercise like running actually suppresses appetite while gentle exercise like walking or swimming stimulates it). The body adapts. It's been much easier to maintain my weight in training for my 2nd Ironman than it was for the first one. Keeping a food journal helped too. Because, duh, what I was eating mattered. A lot. And guess what? I've lost 9 pounds this time around, not that I needed to.

7 comments:

bunnygirl said...

I have found that the initial spike in hunger caused by high volumes of exercise dissipates after ~6 months.

This is my experience as well. It makes sense that when you're in the build phase of your program your muscles need more fuel, but once you enter the maintenance stage, you can level off on your calorie intake.

The sad truth is that a lot of people "reward" themselves with crap food after exercising. Many people don't even exercise vigorously enough to need additional calories, especially if they were overeating to begin with.

Healthy size/weight is no secret. It's real foods in real amounts, and daily physical activity.

I've had far more hunger cravings triggered by crappy, chemical-laden pseudofoods than by exercise, and I didn't maintain my teenage body into my 40s by taking slow, ten-minute strolls on the treadmill and following up a stack of Chips Ahoy cookies.

Renee said...

I have had several friends (non-exercising ones) email me that article who know that I have been struggling with losing weight and also know that I work out a lot. It has been hard not to be offended or make snide comments back to them. I can also see that the author has valid points about eating more after exercising, but it still ticked me off because I feel like it discourages people from even trying to work out. They could read that and think, "Why bother?".
I may be overweight, but I am still going to exercise because I love it. It gives you a high, self confidence, and not to mention the health benefits.
All of this comes down to common sense. Exercise more, eat less, live a long and happy life. It is what I am trying to do no matter what "research" says otherwise.

Wes said...

It's always been about being able to control what you put in your mouth. I haunt some fitness/diet web sites, and everybody there knows that you have to maintain a (healthy) deficit, and if you aren't counting calories, you are dieting via guess work...

Try-a-thlete said...

Thank you for posting this Rachel!

Kate said...

Thanks for the great commentary on this. I totally agree with you, and have struggled to maintain/lose weight while exercising. But that's because I eat too much- duh! It's partly the hunger-spikes, partly the "rewards" and partly trying to find that balance between eating enough to fuel and eating too much.

skinny latte said...

Lots of food for thought here Rachel.

I completely agree with you - exercise and a good diet are both crucial for health, and especially if you want to lose weight. And it's definitely hard to curb these hunger spikes that come with vigorous training.

I personally have got into great shape since I started training for my half marathon, and I don't think I've overdone it on the fuel/food front because I can definitely feel a difference in my body. I feel fantastic and I've definitely toned up but I don't think I've lost weight per se (I don't own scales so I don't know for sure) because I've had to eat more, or certainly eat food with more dense energy value. You really do have to eat so much more to be able to do those distances, I've realised!

But at the end of the day I'm exercising for the love of it, and I'm training for these events because I love the sport and want it to be a big part of my life. As long as I can stop fuelling turning into overeating I think I'll be ok!

I like your idea of tracking and keeping a food journal - that definitely helps too!

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