Exercise v. Diet for Weight Loss

In recent months, mainly sparked by Mr. Exercise Only Makes You Hungry's appearance on the Dr. Oz show, there seems to have been some renewed interest in the LC community in the role of exercise for weight loss.  Most studies show little effect of exercise only, but, as the authors of this study I'm about to share state,  "these conclusions are drawn from studies in which individual energy intake and expenditure were not rigorously controlled or accurately measured" .  When it has been controlled, the calorie deficits created through exercise alone were not sufficient to produce significant weight loss.

This study was done in weight stable (6+ months prior to study) obese (BMI >27) men with waist circumferences over 100 cm (~39").    The men were sedentary, non-smokers, non-light drinkers, and had normal lipids and glucose tolerance.

They were randomly assigned to four groups.  There appeared to be a fairly high drop-out rate reported for all groups that you can go see for yourselves.  The four groups:

  1. Control (C):  No exercise or dietary caloric deficit
  2. Diet Induced Weight Loss (DWL):  No exercise, prescribed 700 cal deficit CRD
  3. Exercise Induced Weight Loss (EWL):  Diet maintained at maintenance levels, exercise prescribed to expend 700 cal/day (treadmill brisk walking or light jogging)
  4. Exercise Without Weight Loss (EWW):  Exercise (same as EWL) to expend 700 cal/day with intake increased to compensate and maintain weight.
The treatment phase of the study was 12 weeks.  Although free-living, all subjects kept and analyzed detailed daily records.  Obviously, in an ideal world, this would have been an in-patient study or foods provided, etc., but daily records for this length of time are better than most studies include.  The exercise was supervised and caloric expenditure determined using heart rate and other measures (this is a significant improvement over exercise studies where exercise is not supervised to verify compliance and/or intensity).

All subjects ate a "standard" relatively low fat high carb diet:  55-60% carb / 15-20% protein / 20-25% fat

Baseline maintenance levels were estimated then confirmed over a 4-5 weeks prior to treatment.  After treatment, all subjects again ate and were monitored to determine weight maintaining energy levels.  TDEE was also measured for two weeks using double-labeled water technique midway through the study (weeks 6-7).

They measured body weight, composition and various metabolic parameters.  These are shown below in a summary table I crunched down from the split tables in the original text.  {click to enlarge}

Below are the changes in various parameters for the two weight loss groups

It should be noted that only the total fat loss (4.8 for diet vs. 6.1 kg for exercise) and maximum oxygen uptake differentials rose to a level of statistical significance.  However most all differentials in fat mass trend towards favoring the exercisers while they tended to retain more skeletal muscle mass.  The notable exception was for subQ abdominal fat where exercisers oddly enough saw a modest increase compared to a modest decrease in the dieters which produced a modestly smaller reduction in waist circumference.  The authors acknowledge that in the end their study was "underpowered" due to the high dropout rate resulting in relatively low group sizes.  

I'm not sure what to make about the TDEE data (shown below).

In some ways I would say it pretty much throws all of the results into question.  Why?  Well, the intake was self-reported.  Could the control group have been underreporting?  Otherwise the dieters only actually achieved about a 50% greater caloric deficit vs. the control group.  And, the C's had a rather significant calorie deficit, that, if sustained for 12 weeks would have resulted in about a 5kg loss.  Yet, the controls maintained weight.  Or was there a problem with the EE measurement?  The almost 500 cal/day differential for the DWL vs. C seems a bit extreme to have been merely metabolic compensation for the somewhat modest 700 calorie restriction.  

Looking at DWL and EWL, and allowing for some irregularities in reported intake and/or measured EE, the energy deficit was statistically different for EWL vs. DWL group.  

But what is everyone always saying about weight?  It's the fat loss that matters, not weight.  In this regard, this is yet another study demonstrating greater fat loss when the deficit is accomplished through exercise vs. caloric restriction.  Plus, the exercisers get to eat more.  Things that make you go hmmmmm.....

Now, it should be noted that the exercisers had a bigger drop in fasting insulin.  So that must be it?   Well, the exercise results in improved insulin sensitivity.  Peripheral IR seems to mostly be related to non-oxidative glucose disposal, aka glycogen synthesis.  When glycogen stores are topped off this route is blocked off.  Exercise - all sorts - does what?  Depletes glycogen.  It also requires fatty acids.  Makes sense to me that insulin is reduced in response to the exercise.

Exercise, it appears, is highly underrated for FAT loss.  I better get my ass moving!


Ptmikem said…
The benefits of exercise are endless not only in helping weight loss. When it comes to weight loss it is about inches and not pounds. Many people put to much emphasis on what the scale reads.
Exercise and Nutrition Tips
mem said…
<"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 — or, for that matter, from magazines like this one.

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.>

Read more: http://www.time.com/time/health/article/0,8599,1914857-1,00.html#ixzz1KHgBK2eL
Anonymous said…
Exercise will always be bested by diet in the weight reduction contest... for most people.

The reason - and it has nothing to do with hunger and 'hunger caused by exercise' - is that it takes so long to burn x number of calories exercising when you can simply EAT 2x number of calories in a minute or two and tip the balance of energy.

Also, you may enjoy every delicious minute of eating those calories. (I might even eat those calories while I'm watching TV! My favorite: pizza and Saturday Night Live...)

Exercise, on the other hand, is not always so pleasant. You might not enjoy that time spent exercising. (Note to self: my neighborhood Y now has TVs to watch while you cycle, walk, run, climb the Stairmaster. Wonder if I can manage pizza on the Stairmaster.)
CarbSane said…
Welcome mike & mem!

Mem, Cloud's assertions are simply not backed up by the studies. Yes, some overestimate their caloric expenditures and engage in too much compensatory/reward eating (see:http://www.bodyrecomposition.com/research-review/normal-weight-men-and-women-overestimate-energy-expenditure-research-review.html for example). Time and again when people simply track and make sure not to, however, they lose fat and preserve their metabolic rates.

I'm very interested in that moving forward from this point.
MM said…

This is unrelated to the point of the post, but I just have to ask. Are these people actually considered to have "normal glucose tolerance"? Yes, their fasting numbers are normal, but look at the OGTT numbers. At 2 hrs they were in the 500s. I looked at it several times just to make sure I wasn't seeing things. Correct me if I'm wrong, but doesn't that make them diabetic? I suppose whether they did this study on "normal" obese people or type 2 diabetic obese people is probably irrelevant. I was just shocked at the OGTT numbers. Maybe you can tell me if I'm looking at it wrong.
CarbSane said…
Hi MM: Those are areas under the glucose curve.

Before treatment and approximately 6 days after treatment, a 2-hour, 75-g oral glucose tolerance test was administered the morning after an overnight fast. Blood samples
were collected from the antecubital vein at -15, 0, 30, 60, 90, and 120 minutes. Glucose was measured by using an automated glucose analyzer (YSI), and insulin was measured by using a radioimmunoassay kit (Intermedico, Toronto, Ontario, Canada). Areas under the glucose and insulin curves were determined by using a trapezoid model (33).

The glucose x 2hr designation in the table is confusing. If they had 500's at 2 hrs that would be superdiabetic!!
Bill said…
Haven’t gotten to the full ms yet, but why did the control and ‘exercise without weight loss’ groups exhibit similar changes in fat mass despite controls eating a 466 calorie/d deficit and ‘exercise without weight loss’ eating a 55 calorie/d surplus? I agree, something is awry.

also, is “the exercisers get to eat more” really that much of a benefit when it might seem like they are eating just as much? (jk)
MM said…

Oh thanks. Missed that about AUC. Glad they didn't consider 500s to be "normal". :)

I am unfamiliar with what is normal for AUC glucose values. I was able to find this from www.omicsonline.org/2155-615/2155-6156-2-125.pdf

" normal (AUC glucose
< 960 and AUC insulin <= 75500), high AUC insulin (AUC insulin > 75500) or
high isolated AUC glucose (AUC glucose ≥ 960 and AUC insulin ≤75500)"

Sort of wish I could find something that differentiates between normal, pre-diabetic and diabetic, but this was the best I could do with my quick search.
CarbSane said…
Welcome DrLagakos! Yes, something is fishy on that front and I am disappointed the authors did not address the discrepancy. Still - I'm left with the changes in fat mass for exercise v. diet that are consistent with now several studies I've come across and blogged on.

Does this bring into question the accuracy of TDEE measurements? Perhaps.
Muata said…
I find the whole "exercise makes you hungry" a a poor excuse and something that sedentary (read: lazy) diet authors want their obese followers to believe.

There's absolutely nothing wrong with working up an appetite, but that doesn't mean you're given a license to overeat.

To believe that walking on a treadmill for 30 mins, 6 days a week is going to give an obese person such a ravenous appetite that he would've been better off sitting on his ass is just silly.

If we all agree that our bodies are meant to move and our sedentary lifestyles are partly responsible for obesity, why would advocating moving/exercising EVER be a bad thing?

Also, CS, I won't address the argument that exercise is good for general health but not weight loss ... huh?
CarbSane said…
Hi Muata, I harken back to my youth and the leanest periods in my adult life. What do these have in common? Very high activity. By the EMUH theory, I should have been more obese because all that activity would just have made me insanely hungry -> overcompensating. But this just isn't so.

It is my belief that the "hunger" most experience doing an ELMM approach is due to over-obsessing on the EL part. To me this is the glory that is low carbing because calorie restriction occurs naturally. When I counted calories it was always thinking about when I could eat next, how much, etc.

MM seems to work very well, better even in the long run, so long as folks are just aware not to change their eating.
CarbSane said…
@MM: I'll have a look. Meanwhile stay tuned cuz I just came across an interesting article regarding differences between postprandial IGT (impaired glucose clearance) and elevated FBG (liver IR = impaired gluconeogenesis control).
MM said…
Cool. Looking forward to it. :)
Sanjeev said…
> Mem, Cloud's assertions are simply
> not backed up
I had a response typed up, just missing some citations but could NOT remember the sources. Frustrating.

Lyle's been repeating that thing for as long as I've read him: activity may not help an obese person lose fat mass but activity is one of the predictors of long term adherence.

It's all about the long term. Losing 50 pounds is meaningless if you have to do it again 2 years later.

Muata said...
> I find the whole "exercise makes you
> hungry" a a poor excuse and something
> that sedentary (read: lazy) diet
> authors want their obese followers to believe.
this is too hard to sell:

"you may have to work hard and may be uncomfortable (that is, hungry) occasionally"

Even I don't try to sell it - I suggest people find a physical activity they like and they can stick with.
. said…
Energy intake and adiponectin gene expression. http://www.ncbi.nlm.nih.gov/pubmed/21325106
Anonymous said…
Calorie deficits obviously have NOT worked for the vast majority of calorie counters I have seen on the Internet.

You cannot overcome your natural build LONG TERM.
CarbSane said…
Razzwell: Please cease and desist the rants and personal attacks. If you want to rant and rave over me or Colpo or anyone else you think is wrong, you have your own blog for that. We enjoy discussing things here.
Unknown said…
I'm one person that proves in experience that exercise alone, when diet is out of control, is not going to work for weight loss. I've been Biking daily for transportation for 10+ years, and I gained nearly 100 lbs.That's where the hunger control benefit of the low carb diet comes in.

If any of you can explain this to me- why are some of the people in the LC community so adverse to counting calories? Yes it's a bit of a chore at first, but is it worth giving up progress? Part of being an adult is admitting that that you can't have everything you want at the same time, or that it won't come easily.
Unknown said…
BTW eulerandothers, I ate an apple yesterday on the bike while going to work, so it's possible, but If you eat pizza while on the machines at the Y, please post pics! X-D
Anonymous said…
I'm about to share state, "these conclusions are drawn from studies in which individual energy intake and expenditure were not rigorously controlled or accurately measured" . When it has been controlled, the calorie deficits created through exercise alone were not sufficient to produce significant weight loss.
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