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Dr. Ayala

Dr. Ayala
Philadelphia, Pennsylvania, USA
V.P. Product Development
Herbal Water
I’m a physician (Pediatrics and Medical Genetics), artist, and mother of 3 school age active kids. I recently co-founded Herbal Water Inc. (www.herbalwater.com) with my husband, Albert. I am a serious home cook, and love to entertain. My expertise is vegetarian food (I have been a vegetarian all my life). I strongly believe that eating healthy and enjoying good food go hand in hand. My main interests are science, nutrition and art, and I am overall a very curious person that tries to learn something new every day. Dr. Ayala (Ayala Laufer-Cahana M.D.)


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Editor’s Pick
OCTOBER 3, 2012 9:23AM

Study debunks exercise as a weight-loss solution

Rate: 11 Flag


Physical activity is incredibly important for our health.  Exercise improves almost all aspects of physical and mental health, and people who are physically active are also usually thinner.

But that doesn’t necessarily mean that exercise will make you shed extra fat.

The makers of junk and fast food are sponsors of exercise, from backyard games and pee wee leagues to the World Cup and the Olympic Games, and suggest that in this little imbalance we have between caloric intake and caloric expenditure we shouldn’t lay the blame on eating too much but rather on exercising too little.

And it would have been nice if we could go for a brisk walk and forget about inconvenient eat-less guidance. I, too, would like to believe that. But is it true? 

Exercise as a weight-loss tool

A new study in the British Medical Journal (BMJ) looked at 30 randomized controlled trials in which kids were assigned an intervention aimed at promoting exercise. What’s special about this analysis is that the review includes only studies in which physical activity was objectively measured using accelerometry devices (accelerometers measure body movement, and are an unbiased way to sum up activity – they’re much better than asking people how active they’ve been over the day).

The results were disappointing. Kids on exercise regimens added on average only a tiny and negligible amount of active time – about 4 minutes -- to their daily tally compared to controls. These extra 4 minutes would amount to about 15 extra calories burnt. Definitely not enough to justify the sports drink or a fast food meal many kids are rewarded with after they exercise.

How come adding several extra hours of physical activity at school ends up adding close to nothing? Well, one of the explanations the authors offer is that the exercise interventions simply replaced equally intense exercise that would have taken place after school – instead of running in the playground kids were exercising at school. Our natural instinct might be to regulate activity around a set point, and when we expend more than our usual energy we follow that activity burst with inactive periods of rest.

The authors conclude:

Physical activity interventions have little effect on the overall activity levels of children, which may explain, at least in part, why such interventions have had a limited effect on body mass index or body fat. The outcome of this meta-analysis questions the contribution of physical activity to the prevention of childhood obesity.”

Are we exercising less than our ancestors?

Kids need plenty of physical activity. Current recommendations are that kids get 60 minutes a day of any activity that makes their heart race and gets them breathing hard – they need to sweat. Only a third of US kids get that much.

On the other hand, while obesity rates have doubled and tripled over the past few decades, physical activity levels have been quite stable over that time period, and studies have shown that kids today move no less than when the obesity rates were much lower. TV was invented a long time ago.

A neat recent study in PLoS ONE further debunks the notion that our sedentary lifestyle is the culprit in the obesity crisis. The study quantified daily energy expenditure (by measuring carbon dioxide production) among the Hazda people of Tanzania, one of the few remaining populations of traditional hunter-gatherers. The researchers found that despite covering many miles a day in search of food, the number of calories that the Hadza burned was pretty much the same as that of typical adults in Europe and the US.

How could that be? The researchers think that the Hadzas’ bodies have adjusted to the higher activity levels required for hunting and gathering by saving energy on other activities. Our bodies spend energy even when we seem not to move much, and their guess is that these ‘background’ activities can be done more efficiently when energy is spent elsewhere.

That doesn't mean that ecercise is a waste of time. Exercise will make you healthier, and is a key habit change that can open the door to healthier eating and other good habits, some of which can also help with weight loss and weight maintenance.

But there’s very little support for the idea that exercising more without eating less can change your weight.

It’s the food; it really is! We’re getting fat because we eat too much and too much of the wrong things. Our food is tempting and sweet and plentiful.

Leading a sedentary lifestyle is another major health issue, one that should be addressed because physical activity is a wonder power for wellbeing.

But addressing physical activity alone will do close to nothing to obesity rates.

Dr. Ayala

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@Gary Fandango: I hear you...and I'm going out for my run :)
I just had to comment on this: It has taken me 30 years to figure this out on my own. I didn't even need medical docs to verify it for me. I have worked out all of my life, and it has not kept the pounds from creeping on. I ride a road bike, run, swim, weight train, etc., and I have not been able to get the scale to budge in years. Yet, I am very healthy, and can kick just about anyone's butt in the gym.

Fat but fit is my mantra. ... I'll keep trying to lose until my dying day, though. :)
Exercise stimulates metabolic rate, especially if it is varied and inconsistent. That said, you're right that calories rule! As for kids, time playing actively and doing sports is time not sitting at the Playstation or wii nibbling on fattening treats.
Cardio is important but strength training melts the fat like nothing else. A summer of cookouts melts off for me after I start lifting weights even if I do not pound the treadmill.
That is me, if you find something that works, stick with it.
It didn't debunk exercise as a weight loss method. It debunked the fact that forced activity increased the activity levels of those children (basically, when they were forced to participate in these programs, they simply cut their activity levels in other parts of their lives).

They didn't debunk exercise as a means of weight loss, because calories are still a measure of energy, and the burning of energy, both actively being processed in ones digestive system and also the energy stored as fat (and, when the body is desperate enough, the energy available by destroying and processing what can be garnered from ones muscles) is still a proven means of losing weight, if only temporarily.

Looking at a tribe of people who have adapted to use calories more efficiently simply because they encounter them so infrequently is stupid as a scientific method for examining this issue.

Also, mixing boys and girls was stupid, because women use calories more efficiently, and are able to rid themselves of reserve calories less easily (this is accounted for because they are evolutionarily sedentary, and men are evolutionarily on the move, which means that women's ability to gather and ingest calories, for themselves or the offspring it has always been their responsibility to nurture, has been historically hampered by their gender role, and this also affects how they gain and lose weight).

This study was stupid, it was poorly done, and it didn't address a single thing about the link between activity and weight loss, simply the link between forced activity and its relationship to overall activity levels.

Incidentally, one actually study of merit links physical fitness to mental fitness, and is probably the single most important factor in improving American schools. This, of course, also makes perfect sense because while the "mind" may be a separate entity, the brain is fully connected to the physical health of ones body, and when that body is not healthy, the brain is unable to power the mind that allows children to learn.

Man...people will glom onto anything new...milk is good for adults...milk is bad for adults...milk is good for adults...and so on.

Dairy becomes less necessary as one grows in age, but can be included in any well balanced diet, in low to moderate levels, and when done so as such, it is a good source of fat, calcium, and protein...all things which adult humans need to run the factory they call their bodies.

Wonderful post, doc.
Pure facts and harsh truth that most people choose to cover with a plate of nachos!
Also, the only lasting weight loss solution is bariatric surgery. It is the only weight loss method which has shown lasting weight in more than one percent of patients studied over a 14 year or longer period.

The only thing that can lead to lasting weight loss and maintenance is being Richard Simmons or having your stomach shrunk to the size of a thimble.
After you reach adulthood, that is. Kids still have a chance.
There have been times when I have been relatively sedentary, and times when I have been very active. What I've found is that several hours a week of vigorous exercise will make me around 30 pounds lighter than my sedentary weight. The exercise can be biking, running, swimming, martial arts, or whatever. But that 30 pounds is all exercise does for me -- I've never been "thin" from exercising.

One of my coworkers did get thin through exercise. But he was exercising 2 to 3 hours a day. After a few months he discovered that it was impossible to have a career and a family AND spend 2 to 3 hours in the gym every day. He ended up cutting back on the exercise, and within a few months was no longer "thin."

Exercise is great, but the effect of exercise on body weight is fairly limited. Eating habits seem to be much more important.
These results mirror what's been clear for a long while, to me.
It's the calories, yes, but more importantly, the type of calories, in my experience, those 'fake food' calories made from unnatural and unreadable ingredients aren't doing anyone any good at all.
Exercise *does* help prevent the 'dough boy' look : )
I noticed decades ago the number of hours of strenuous exercise it would take to burn off the calories in one candy bar, and decided it would be easier not to eat the candy bar.

Whatever works for a person, that's great, but the only thing that has ever worked for me is to eat less. This was easy to do when I was young and thin and before I ever let myself "go," and much harder to do now that I'm old and it's become real work to keep myself at a normal weight. Exercise is good for you, that's pretty much a given, but I don't think it's a big factor in weight management unless you're a contestant on "The Biggest Loser."
I have noticed that the more I exercise, the hungrier I get. I am able to lose far more weight (with much less pain) by being relatively inactive and eating very little under 700 calories if I work out (up to 50 minutes of cardio and 20 minutes strength training)and eat 1200-1500 calories I gain.
I lost 15lbs in one day riding my bicycle from Seattle, WA to Portland, OR. Actually, I lost 15lbs on day 1 of this trek and 7lbs on day 2. I gained it back, for the most part, within 60 days, but I have no idea what anecdotal stories have to do with the scientific method.
In the end, this is a doctor inaccurately reporting scientific data, and it's an editor's pick.

When Beetle Bailey ends his stint as editor of this joint, will someone sound an alarm or something?
When I was on the 600 calories a day canned food diet, I was told NOT to knock myself out exercising. I forgot the reason, but I was so weak from hunger I couldn't have run across the street to mail a letter!
Compared to a hunter-gatherer society on the move all day, or our peasant ancestors working the fields from sun-up to sundown, what we call exercise is peanuts.

That's why it doesn't work. 30 minutes of aerobic exercise is nice, but not worth mentioning compared to an 8 hour day haying or plowing.
Thanks a lot for this study, It seems to me that the only option is to eat less calories and thus less food to create caloric deficit.
Just moving is a pretty good weigh to prevent weight gain, but restricting carbohydrate and fat intake is generally the way to go to burn fat. You can lose a lot of muscle weight from dieting, and that switches on more fat storage hormones for later when you start eating again. It also drives down testosterone, which is horrible for men, but worse for the women that hardly have any to begin with. Cardio excellent for blood sugar and HDL/LDL balancing, but if you want to burn fat at rest, you need more muscle and bone- and that is made with protein and heavy weights like gary suggested. It does kick up the IGF-1, and changes metabolism- if you do this for long periods of time, like weeks and weeks, not days and days. If you suddenly stop doing all the moving, you have to stop doing all the eating that goes with it, or those fat storing hormones turn on again.
sorry for misspells, at work, typing fast.
"It’s the food; it really is! We’re getting fat because we eat too much and too much of the wrong things. Our food is tempting and sweet and plentiful."

It really truly is, and it's just common sense.
what a ludicrous and irresponsible conclusion.

at the age of 28 i lost 35 pounds over the course of a year, kept it off for a decade.

my dieting modifications were: i switched to skim milk (i drink a couple glasses a day), and i cut back on (not gave up) butter. those were the ONLY changes i made.

i ate cake, and if i wanted a second piece, i ate a second piece. i ate pasta and bread and bacon.

exercise was totally the key.

my son's friends who are lanky, or lean, or perhaps skinny, depending on which i am thinking of, eat just as much gross stuff as he does, and as little that is nutritious. but they are on football or basketball or track, and are very very fit, while my sedentary son is overweight.

i mean, i am sad that as smart as we are, we have no more common sense than this study shows.