Monday, 18 January 2010

Exercise won't make you thin... will it make you fat?!

We learn that the more we exercise, the skinnier we'll be... so we go to the gym- 45 million Americans have a gym membership- or try to get out and do something... and feel guilty if we don't.
The media and shows like the Biggest Loser focus on exercise for weight loss... and it seems to work, right? Not quite.

Time magazine published a great article this past summer: Why Exercise Won't Make you Thin.

The article quotes the Chair in Diabetes and Metabolism at Louisiana State University, Eric Ravussin, as saying:
"In general, for weight loss, exercise is pretty useless."

Pretty shocking statement, eh?

The article outlines a study that found that children that were more active ate more- 100 calories more than they had burned.

It mentions another study that found that overweight people burned more calories a day than 'normal'-weight people.

Hmm. Can that be right?

Just a few days ago, the Center for Disease Control and Prevention (CDC) published its report. They found that obesity rates in the States have plateaued in the last decade. That said, we know that we're bigger now than we ever were- 68% of Americans are overweight and 34% are obese!
We've been led to believe this is happening because we're lazy and sedentary. But maybe that's not it at all.

A 2008 study found that the number of calories we spend a day hasn't changes since the 1980s! But we're fatter than we were in the 80s.... hmmmm.
What's crazier is that the same study found that our caloric expenditure is not significantly different that people in the "Third World"! But we know we're bigger than people in developing countries!

Another study looked at the effect of exercise on weight:
464 post-menopausal women exercised under supervision for 72, 136 or 192 minutes per week, at moderate intensity, on a treadmill or bike, for 6 months.

While fitness improved for those that exercised longer, weight was a different story:

The 72mins/week group lost about 1.3kg,
The 136mins/week group lost about 1.9kg, and
the 192 mins/week group? Same as the 72mins/wk group- they only lost 1.3kg!


Most likely, they were compensating for the extra exercise by eating more.

The Time article points to different studies showing that when we exercise more, we tend to eat more... too much more.

Remember that picture of Bill Clinton stopping in at McDonald's after a jog?

What's surprising is how fast those calories add on.

Let's say you go for a 6km (3.75 mile) run at a decent 5.5 min/km (9 min/mile) pace (and you weigh 140lbs). You burn about 430 calories.

It's a hot day.. you rehydrate by drinking half your Gatorade bottle (500 mL). On the way home, you stop by Starbucks and grab a medium cafe latte with skim and a low-fat muffin... you earned it, right?

You've already consumed 570 calories- 140 calories MORE than you spent! And, chances are, you'll eat more when you go home and you'll probably be more sedentary the rest of the day.

But Doesn't Muscle Burn More Calories Than Fat?

We've learned that exercise builds muscle and that the more muscle you have, the more calories you'll burn. True... but it's not as much as we thought.
1 lbs fat burns 2 calories ; 1 lbs muscle burns 6 calories.
So if you work out like crazy and manage to convert 10lbs of fat to muscle (most of us will never achieve this, btw), you'll only burn an extra 40 calories a day- that's only 4 jelly beans- worth of calories. Not much.

Is it better to stay at home and not exercise? Is exercise making us fat?

Well... exercise is still good for us.
It's good for our bones, it's good for our heart, our lungs, our circulatory system. Exercise increases our good cholesterol, protecting us from strokes and heart attacks. It can help prevent certain types of cancers. It's a mood-elevator, makes us feel better, more alert.

If weight loss is a goal, exercise can be the instigator to eating better... and, in that way can help with weight loss. However, it's the calories we consume (or don't) that will make a difference in our weight... not the exercise.

Excercise won't cause you to gain weight, per se....but the extra calories you eat as a result of exercise will.
We need to be very aware that exercise isn't an excuse to eat foods we normally wouldn't eat (or in quantities we normally wouldn't). It's also not an excuse to be lazy the rest of the day.

Diet Vs. Exercise

If you need more evidence, check out the clip below: Diet vs. Exercise.
What he says is true: "You can't out-train a bad diet"
(btw- I don't agree at all with his statement that "cardio is a joke"- as mentioned above, there are many benefit to all kinds of exercise).


ingy said...

I have to say that when I stopped exercising last year, I lost weight! It was maybe muscle that I was losing though...

I heard a personal trainer once say that exercising counts for 30% and diet counts for 70% of your overall goal.


I was infuriated when I saw that article in Time! I think it's absolutely absurd to say exercise is anything less than an essential part of a healthy lifestyle. As you point out, there are many benefits even without weight loss... I like the ratio ings left: 70% diet and 30% exercise seems like a good way to lose or maintain weight. I also have a question about the numbers for calorie burning: if I weigh 100 pounds that means I can only burn 600 calories even if I'm 100% muscle?? I was wondering if that is how many calories each pound above your ideal weight burns or what exactly the formula applies to.

Sybil Hebert, RD said...

Thanks for your comments Ings and Laurie... I agree with you, Laurie- I like Ings' 70%/30% ratio... while possibly not exactly accurate- it's a nice way to explain it!

I know how you felt, Laurie. I used to work with a physician who talked about the "uselessness" of exercise in weight loss all the time... and it used to make me so upset!

Reading these studies has changed my opinion a bit, but I still think exercise is essential in helping people wanting to lose weight to adopt a different lifestyle that's necessary for weight loss....

As for the calculations- doesn't seem like many calories, eh?

Not the best source but seems to corroborate what I learned in physiology...:
10% of energy expenditure is due to thermogenesis (digestion of food),
20% from activity (of daily-life and exercise),
and 70% of energy expenditure is due to BMR (processes taking place within organs).
The breakdown of energy expenditure in the body:
18% of from muscle (so I guess this is what changes with increased muscle mass),
27% from the liver,
19% from brain
10% from kidneys
7% from heart
19% from other organs


I'll contact an exercise physiologist friend to see if she can check this info!



Hey! I just love that division of how your body burns calories. It totally makes sense that the organs are not counted with the "muscle" for contributing to metabolism--I get it now!

Melissa said...

I believe we need to listen to our bodies more; this is what works for me. I feel my absolute best when I am eating mostly vegetarian (minimal amounts of dairy and occasional fish) and build muscle. However, the same exact eating for my fiance does not work. (He feels best eating mostly vegetarian but occasional meat-based meal and doing more cardio than muscle building.) When he ate just like me, his energy plummeted.

I take knowledge of others (MDs, scientists, RDs, HHCs and integrative physicians) and through trial and error, see what works for me.

just my two cents

Sybil Hebert, RD said...

Great advice, Melissa!

Unknown said...

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