Adolescent Obesity - The Misinformation Continues

December 14, 2008

As some of you know, I am certified by the American Council on Exercise as a personal trainer. ACE as it's called for short, is one of the largest if not THE largest certification trainer agency in the world. You'd think that an organization of this size and strength would be vigilant in putting forth correct information especially regarding adolescent obesity.

Not a chance. Pardon my pretentiousness, but they won't even recognize the existence of my new book Strong Kids Healthy Kids.

In the most recent issue of their magazine ACE Certified News (a magazine to keep trainers informed of the current science and research in the field), there is an article titled: Exercise in the Prevention and Treatment of the Childhood Onset of Adult Disease written by Natalie Muth, M.D., M.P.H., R.D.

As many of us know, children today are suffering the same age-related outcome conditions (not technically diseases) as adults such as obesity, type II diabetes, arteriosclerosis and heart disease, fatty livers, high blood pressure, low grade inflammation, etc.It's a terrible thing that is happening to kids but what is even more evil is the continued misinformation about the causes and cures.

While much of Dr. Muth's article is informative and on point, it is also fraught with such a high level of misinformation that I really don't know where to start. And this saddens me because Dr. Muth is just one of thousands of doctors who continue to propagate the idea that a lack of physical activity is a major cause of adolescent obesity. 

Here's a quote from the article (I guess I'll just randomly pick, choose and dissect - it's sort of funner that way!):

"Obesity is the major cause of insulin resistance, the precursor to type II diabetes."

Um...huh? I think Dr.Muth got that a tad backwards - and sideways. Obesity is not the cause of insulin resistance. There are millions of obese people who are not type II diabetics. If anything can be said, insulin resistance leads to obesity. I boldly state that insulin resistance, caused by an over indulgence of carbohydrate, is the major cause of obesity.

According to Gary Taubes, author of the amazing book Good Calories Bad Calories:

"As for insulin resistance, here's my take. We only accumulate fat when the
lean tissue is insulin resistant and the fat tissue is insulin sensitive. In
someone who becomes obese and then diabetic, the lean tissue first becomes
insulin resistant, and so they start storing calories as fat. When the fat
tissue becomes insulin resistant, the only thing they can do with rising blood
sugar is pee it away and so they do -- hence diabetes. In a lean person, the
lean tissue is as insulin sensitive (or more so, perhaps) then the fat tissue.
 Now if they start to get insulin resistant and it happens simultaneously in the
fat and lean tissue, they still won't accumulate excess fat, but they will
become diabetic. The whole key is whether or not the fat tissue retains its
insulin sensitivity. The longer it remains insulin sensitive, the fatter the
person becomes before manifesting diabetes."

Let that sit for a second.

The article goes on about how important exercise is to control blood sugar levels as too much blood sugar leads to insulin resistance. Very true. Here's a thought - if we didn't eat so much sugar and carbohydrates in the first place, we wouldn't need to behave like hamsters on a wheel. Sadly, the article makes no mention of such an intervention. (Note that the USRDA food pyramid suggests that 80% of what we eat is sugar in all its diverse forms!)

So, rather than suggest that a breakfast consisting of a bowl of Cheerios (sugar), with skim milk (primarily sugar), slice of whole wheat toast with jam (sugar), glass of OJ (sugar) and a piece of fruit (sugar) may be a bit too much sugar for a kid to eat in one fell swoop (and that's just breakfast sports fans!), run her like a sled dog for 60 minutes a day instead. Does it ever occur to these folks that if a kid needs this much daily activity to keep blood sugar levels low there might be a reason? 


"Hey - look at all the acne that kid has from all the junk and refined carbohydrates he eats. Light bulb remedy! Buy extra Clearasil!" Yeah, that's the ticket!

OK, onto exercise and activity and the myth that this helps kids get lean. And it is just that, dear reader, a myth.

In the article, Dr. Muth brings to our attention a summary analysis (also called a meta analysis) done by Evan Atlantis and colleagues called 'Efficacy of exercise for treating overweight in children and adolescents: a systematic review.'

Dr. Muth states:

"A summary analysis of the studies conducted on the role of exercise in the treatment of childhood obesity found substantial benefits, including about a 6.5 pound weight loss over 14 weeks at 155-180 mins. of moderate intensity exercise per week." (By activity she means aerobic-type activity.)

Sorry doc - that is NOT what the meta analysis showed. For shame.

First of all, most if not all meta analyses are painfully useless due to the subjective selection process
of the papers included and the lack of continuity and comparability of the different
studies. In sum, they usually don't tell us squat. Worse, these sorts of papers misinform as is the case with this one.

The paper did not show what Dr. Muth stated it did. I'll bet ya dimes to donuts that Dr. Muth only read the abstract of the study (the shortened version) and not the full text of the study itself. Let me expand.

The researchers found 645 papers that were relevant to the subject of exercise and adolescent obesity. Of the pool of the 645 they found, there were only 45 that they felt were relevant. (And let me add that some of the ones they left out should have been included without question). Of the 45, only 14 made the cut. Of the 14 only 5 of the studies used aerobic exercise alone. The other 9 were a combination of aerobics, diet + aerobics, and diet + aerobics + weight lifting.

Paging Dr. Muth....

When you read the analysis, you see that these researchers worked awful hard to weed out any confounding variables to the point where your head spins. It is clear they were looking to prove that physical activity alone positively influences body fat loss in children. A cardinal 'no-no' in research design. 

Seven sentences into the Discussion section, the researchers state:

"Much of the evidence stemmed from studies of moderate to high intensity aerobic exercise plus behavioral interventions for dietary restriction."

The bolding is mine. Dr. Muth missed this eensy-weensy little tidbit of info.

To illustrate this further, Atlantis et. al. cited two studies in their meta analysis used as proof that:

"In adults, weight training has been shown to be superior to aerobic exercise for the maintenance of fat free mass during dietary restriction while aerobic exercise and weight training exercise in combination was found to be superior to either modality alone for decreasing whole body fat during dietary restriction."


First, neither study cited in the paper as proof that the combo is better included a strength training only group. So you can't state that the combo of aerobics and strength training was superior to strength training only if a strength training only group wasn't included in the study. Now, to be fair, there may very well be research out there that supports this opinion (no there's not but I'm throwing them a bone here), but the studies cited don't.

In fact, the better of the two studies showed that aerobic exercise only contributed to just over a half pound of fat loss more than the diet only group. Better 'tis true, but don't jump to any conclusions. At face value you'd think that it was the extra calories expended from the aerobics that aided the diet + aerobics group. But a careful look at the study reveals something else.

Let's look at some of the details. We'll start with the loss of lean mass.

After 12 weeks, ALL 3 groups lost some fat-free (lean) mass (muscle, bone, etc). The diet only group lost 3 kg, the diet and aerobics group lost 2kg and the group that had strength training included lost  0.2kg of lean mass - in other words, virtually nothing.

As for total mass lost (fat and lean), the diet only group lost 9.64kg. The diet and aerobics group lost 8.99kg. The diet, aerobics and strength group lost 9.90kg. (It's interesting that the diet and aerobics group lost LESS total body mass than the diet only group, right?) But as revealed above, they lost less lean mass. You'd think that the aerobics group would have lost enough extra fat to exceed the total mass lost than the diet only group, but no.

What's goin' on here? To quote Mr. Holmes: "It's elementary Watson!" (That just popped into my head so I wrote it.)

Percentage wise, here's how the groups fared. Of the total mass lost, the diet group lost 69% from fat. Diet and aerobics lost 78% from fat and the diet, aerobics and strength training group lost 97% from fat.

Now, doing the math - this means that the diet only group lost 6.7kg of fat and the diet and aerobics group lost 7kg of fat. As mentioned earlier in this post, that's a loss of just over a half pound of fat greater for the diet and aerobics group. A little better, but certainly not what you'd think would happen. You'd expect a much better outcome for the addition of aerobics. Maybe the aerobic program was shoddy?

Nope. The aerobics group worked hard because they significantly improved their peak oxygen consumption by 24% and greatly improved their aerobic power 15.4%. So these people were truckin'.

Basically in terms of fat loss, the two groups (diet and diet and aerobics) were in a dead heat especially when you compare them to the diet, aerobics and strength training group which we'll do now. 

The group that performed all three - or should I say the addition of strength training - skyrocketed the fat loss results. In fact, this group lost 9.7kg of total fat. A whopping 40% more than the diet and aerobics group.

Following me thus far? Let's keep going.

Now here's the question - was the extra half pound of fat lost in the diet and aerobics group caused by the added calories burned via the aerobic exercise OR was it caused by the preservation of more lean mass?

We can see from the strength training group that the more lean mass preserved the greater the level of total fat lost. So it stands to reason that the greater lean mass was the true cause of the added fat loss in the aerobics group - at least it is theoretically possible. IOW, the greater metabolic rate of the preserved lean mass burned the extra calories over the 12 weeks in the aerobics group. To further support this idea, there are several studies on adolescents and strength training alone that show a significant loss of body fat from a mere 30 total minutes of weight lifting a week. A mere 30 minutes. You don't burn that many calories in 30 minutes do you?

I go through all this to make you keenly aware that just because a study says this or a medical doctor with loads of acronyms after her name says that, it doesn't make the information true. Not even close.

And the saddest part of it all is that, once again, the misinformation regarding physical activity as a cure for adolescent obesity continues squelching the real antidote which is eating less total carbohydrate and strength training.