The "Myth" About Exercise? Gimme a break

Aug 10 2009 Published by under Cycling


BikeMonkey Guest Post
PalMD, Isis the Scientist and Dr. Charles have been talking a little bit about restarting fitness and dieting regimens, a topic in which I have a small interest. The cover of the August 17, 2009 issue of TIME magazine insists that "Of course it's good for you, but it won't make you lose weight. Why it's what you eat that really counts." Turning to the feature article on Health penned by John Cloud, all I can note is that the stupid not only burns, but it incinerates all logic and sense for a five block radius. I had trouble getting past the second paragraph:

As I write this, tomorrow is Tuesday, which is a cardio day. I'll spend five minutes warming up on the VersaClimber, a towering machine that requires you to move your arms and legs simultaneously. Then I'll do 30 minutes on a stair mill. On Wednesday a personal trainer will work me like a farm animal for an hour, sometimes to the point that I am dizzy -- an abuse for which I pay as much as I spend on groceries in a week. Thursday is "body wedge" class, which involves another exercise contraption, this one a large foam wedge from which I will push myself up in various hateful ways for an hour. Friday will bring a 5.5-mile run, the extra half-mile my grueling expiation of any gastronomical indulgences during the week.

30 minutes? Maybe "an hour"? Four workouts per week for which the only one potentially useful for acute weight regulation purposes is the single 5.5 mile run? And from this the article claims that "exercise" is not useful for weight management?
AAAGGGGGGHHHH!!!!!11!!!!!!


First let me wear my anecdote hat. The regimen described by John Cloud is just ridiculously small when it comes to calorie burning. Most people don't realize this because they don't regularly engage in exercise to the point at which it becomes overwhelmingly obvious they have burned a boatload of energy. I refer, of course, to the bonk. The hunger knock. I think most serious cyclists (and the longer distance runners) are aware of the point at which the body just shuts down. I'm not talking about questionable fitness levels, illness or unusually hard efforts. In the reasonably well-trained cyclist there is a certain amount of time (modulated by ride difficulty) beyond which one can continue to perform at a high level, only by consuming some sort of calorie source during the ride.
Personally, this duration of time is somewhat over an hour (yup, even after overnight fasting) and no more than about two hours (at peak conditioning). If you know your body, read, have done a lot of accidental experimentation with not eating enough on various rides over the years, you will start to accumulate some idea of the variability of the bonk onset. You will notice that it can hit slowly or extremely rapidly and that the variables seem to have something to do with fitness.
This brings me to two papers on "time to exhaustion" which is in a body of research papers which are more or less directed at the practice of carbo-loading for sustained athletic performance.

Effect of carbohydrate availability on time to exhaustion in exercise performed at two different intensities. Lima-Silva AE, De-Oliveira FR, Nakamura FY, Gevaerd MS. Braz J Med Biol Res. 2009 May;42(5):404-12. [DOI]
Manipulation of dietary carbohydrates after prolonged effort modifies muscle sarcoplasmic reticulum responses in exercising males. Duhamel TA, Perco JG, Green HJ. Am J Physiol Regul Integr Comp Physiol. 2006 Oct;291(4):R1100-10. Epub 2006 May 11.[DOI]

The first study used "seven healthy fit men, but not competitive athletes" and the second used "male volunteers who were recreationally active but not exercising on a regular basis" as research subjects. I will resist the tendency to geek out over VO2max, lactate thresholds and such-like but the important point is that subjects rode a stationary bike in the lab to the point of exhaustion, aka "volitional fatigue" and/or a failure to complete 1 min of exercise at 125% of VO2max (oops, I did it). The protocol was similar for the two studies in that subjects first underwent an exhausting exercise pre-condition followed by two (the first study) or four (second study) days of dietary manipulation of carbohydrate balance. Data come from the post-dietary-manipulation retest.
When performing exercise under the lactate threshold (colloquially you can consider this the aerobic/anaerobic threshold) subjects in the first study lasted about an hour (mean 57 min; SD 25 min) and there was no effect of a 48-hr preceding interval of low carb or moderate carb diet on time to exhaustion. The subjects in the second study lasted a mean of 67 min (SE 6 min) after four days of lo-carb diet and 103 min (SE 9 min) after four days of hi-carb diet. The diet manipulations are not my main point here, I'm just pointing out that experimental laboratory conditions point to the same one-hour threshold for exhausting readily available energy stores as does my anecdotal experience. Some people seem to insist on such verification.
Now, that 60-90 min interval seems to remind me of something or other being bruited about the intertoobz of late...what was it, what was it......oh yes. The good Dr. Isis has been obsessing over:

In order to achieve weight loss, the American College of Sports Medicine recommends 60-90 minutes of exercise five days a week.

Yup. I don't doubt this one bit and I suspect it has everything to do with regularly running the body out of readily available energy stores, i.e., glycogen. This suggests my conceptualization of the real "fat burning zone", not to mention my gut feeling that the TIME author, John Cloud, had no idea what constitutes real exercise. He said "I have exercised like this--obsessively, a bit grimly--for years". Yet apparently he's hitting an hour of sustained aerobic exercise at best twice per week.
Well, no wonder he thinks exercise can't reduce weight...he's not actually exercising in a way that maximizes calorie burning.
Now, before you start slavering away about how stupidz it is for me to join a conversation about mid-life issues in weight-reduction and fitness attainment with unobtainable youth-focused standards which will injure people if they try to reach them immediately, let us not insult anyone's intelligence here. I'm sure you are reading all the posts from Isis and the good doctors Pal and Charles, as well as the following commentary. This is, if you think about it for half a second, coming at the same issue from another direction. Sure it is difficult to find the time to put in 90 minutes of real exercise 5+ days per week. If, however, you expect exercise alone to do the job (holding your current diet fixed) this is what you are going to have to do. The alternative is to cut your dietary intake, no?
__
additional reading
Supercompensated glycogen loads persist 5 days in resting trained cyclists. Arnall DA, Nelson AG, Quigley J, Lex S, Dehart T, Fortune P. Eur J Appl Physiol. 2007 Feb;99(3):251-6. Epub 2006 Nov 22. [DOI]

37 responses so far

  • Markk says:

    Absolutely - I can do 40 minutes a day of running 5 days a week and I won't lose weight, (and I am 100+kg - that sounds better than 225 lbs) but bicycling for 5 or 6 hours a day while eating more just melts it off.
    I think regular daily exercise helps more by stopping you from munching than the actual calories.
    By the way, you understand what energy means to your body once you have really bonked. You just shut down. I mean you can move somewhat but ugh.

  • bill says:

    Why should it be necessary to exhaust energy stores? Assuming you are at a stable weight because energy in = energy out (roughly), then if you add exercise and don't alter your food intake, energy in

  • drcharles says:

    thanks for your 2 cents, and your bottom line conclusion seems valid.
    i'm getting so many spam diet blog trackbacks out of this, my spam folder is overfilled!
    no more diet talk for me after this for a while. like deep fried twinkies, i'm swearing it off before i begin 🙂

  • Curt Fischer says:

    Color me confused.
    Well, no wonder he thinks exercise can't reduce weight...he's not actually exercising in a way that maximizes calorie burning.
    If you replaced "calorie" with "fat", I would agree with you. But you don't have to burn fat to burn calories. If you burn off your glycogen stores, how do they get built back up? From fat? From food? Either way, we start talking about complexities. Sure, these complexities may be beyond John Cloud's ken, but doesn't the framing of your post also fail to consider these complexities?

  • I understand that there are many nuances to metabolism, exercise, and weight loss... but it continually boggles my mind that there is so much debate over how to lose weight.
    Weight loss is described by a simple energy balance:
    Weight loss (lb) = (calories out - calories in) / 3500 (calories/lb)
    We control our 'calories in' by restricting what we eat and we control our 'calories out' through exercise. To imply that either one of these contributors just doesn't matter is ludicrous. And *of course* you can lose weight through only dieting OR exercise, it will just take longer.
    Same with workout duration and/or intensity. Just because you don't have 1 hour every day to go for a run doesn't mean you can't increase your caloric output. If you take the stairs instead of the elevator every day for say, 350 days, you've shed one pound that would otherwise still be stuck to your gut. The *time frame* involved here is what most people find unacceptable and disheartening.
    The bottom line is that *everything counts*. It's one thing to talk about how to most efficiently lose weight, it's another to talk about how to do it at all.

  • bikemonkey says:

    Yes CE but for non-EngineerAmericans there are motivational and volitional processes which get in the way of simple physiological engineering you see.

  • Bardiac says:

    I think it's telling how much he seems to hate the exercises he does, and how he rewards himself by indulging in food. If he were really enjoying the exercise, at least he'd be having fun, no?
    It's still hard to lose weight, but at least fun exercise is fun in itself.

  • Zuska says:

    When my elderly, completely non-active mother was diagnosed as diabetic (type II), she switched to eating in the manner recommended for diabetics. She did cheat now and then, because my mom has an awesome sweet tooth, and a mighty hankering for Cheetos, but more or less she stuck to it pretty good. Just following the recommendations for eating for people with diabetes, she dropped about thirty pounds over the course of year, completely without increasing her activity level, which was zero - she was housebound, and spent nearly all her time in her favorite overstuffed chair keeping up with her soap operas, The Price Is Right, and any Pittsburgh sports team that happened to be playing that day.
    I'm not recommending the no-exercise lifestyle. Just saying, there may be something to be said for looking into the recommended diet guidelines for people with diabetes.

  • natural cynic says:

    I heartily second Bardiac's comment that Cloud seems to have to drag himself to the gym. He needs to find something that is more fun than what he is doing.

    When performing exercise under the lactate threshold (colloquially you can consider this the aerobic/anaerobic threshold)...

    Call me picky, but lactate threshold is the more accurate term. Muscles do not get anywhere near an anaerobic condition at this particular intensity [as in lowered pO2}. Think of it as overstimulating glycolysis so that excess pyruvate is turned into lactate. The muscle fibers that have fewer mitochondria will be producing some lactate and most of it is used as an energy substrate for adjacent muscle fibers that have more mitochondria. Only a small amount of lactate really gets into the circulation. Graphically, lactate increases linearly at a shallow angle up to this point with increasing intensity. Above that intensity, lactate production increases at a much steeper angle.
    Something that needs to be appreciated is that the longer you exercise at a given intensity, the mix of glycogen [and blood glucose] and fat changes, so that a higher proportion of fat is providing energy at 45 minutes than at 15 min.
    Kurt

    If you replaced "calorie" with "fat", I would agree with you. But you don't have to burn fat to burn calories. If you burn off your glycogen stores, how do they get built back up?

    You are always utilizing a mix of fat and carbs if you are exercising aerobically. Glycogen stores are replenished from blood glucose, almost all of which comes from food. So if you exercise for 60-90 min., eat some carb rich food soon after finishing.

  • Evidence Based? says:

    I understand that TIME is feeding us crap. The question remains... are exercise and diet helpful in controlling weight *for meaningful amounts of time*.
    As anyone who has seen their weight rise and fall over the course of diets, the last clause, *for meaningful amounts of time*, is critical.
    It is my understanding that there are precious few controlled studies that show an ability to maintain a reduced weight over an extended period of time through diet and or exercise.
    So... can someone show me a controlled study which yielded significant weight loss after 2 years?

  • pete says:

    As a matter of fact exercise does burn calories but it is a puny and totally ineffective attempt at losing weight. Anyone can check this fact by looking at a food-calories table and an exercise-caloric expenditure table. All the calories you burn cycling vigorously up and down for hours are EASILY regained with typical fast-food servings washed down with sodas and similar. A single slice of pizza may pack as much calories as one hour jogging on a treadmill would spend. Lots of people would not be satisfied with less than 3 such slices for one meal.
    It is a losing battle and experience shows people may exercise as much as they could but if they do not limit amounts of food and feel constant hunger they will NOT lose weight. They will get strong, ok. But fat too.

  • clamdigger says:

    There is a simple moral here: Exercise to burn more calories than you take in. The result will be weight loss. Many different combinations of diet and exercise can achieve this result if the bottom line remains the same. That being said, not all combinations are attainable for a busy person, or necessarily healthy.

  • Eileen says:

    An extra half mile is supposed to be “grueling expiation?” Don’t make me laugh. In what universe is this going to counteract A WEEK’S WORTH of overeating? It wouldn’t even pay for one decent cookie!

  • Queazel says:

    Anyone care to explain what "bonking" means in this context? Here in Australia it only means one thing (much as "bum" does not mean "homeless person" in this country). I've never heard "bonking" used to refer to exercise (other than that one specific, usually horizontal kind of exercise).

  • JLowe says:

    Notice the other thing he wasn't doing - strength training. In a fat loss program, it's not going to help you build muscle, but it might help you hold on to what you have, so that a larger proportion of the weight you lose is as fat. Over time, you "gain" muscle (or a higher percentage of your body comp is muscle as you lose fat) - so, you can work more for the same perceived exertion - so, you can burn more calories - and burn more fat.

  • Evidence Based? says:

    There is a simple moral here: Exercise to burn more calories than you take in.
    If it were that simple...
    The loss of weight causes the body to react in non-simple ways. The results prime one for rapid weight gain following "famine." This is ideal for an animal living 10,000 years ago... but is a health disaster in extended times of plenty.

  • Bardiac says:

    "Bonking," in US cyclist circles at least, means not (alas) having sex, but getting to the point where you feel like you just can't push one bit further. It happens when you use up all the easy-to-use stored energy on a ride or run. That's why real cyclists (as opposed to people such as myself) eat during those long races and rides, including all sorts of energy gels and such.

  • bikemonkey says:

    queazel, it is sort of hard to explain in full for someone who hasn't experienced it. Everybody knows when they've exercised at too high an intensity and get too tired to continue, lose volition to contine, etc. This is a little bit different- when you are bonking (no not that kind) you just run down like a weak, exhausted battery and cannot do anything about it from a will power stance. Resting for 10 min doesn't do any good either. However if you eat a banana, chug a gel, something like that, you perk right up in 15-20 min. come back and do the same ride next week but remember to consume enough easily deployed calories and you'll cruise right through...

  • queazel, it is sort of hard to explain in full for someone who hasn't experienced it.

    Or, you know, there might actually be some data out there somewhere...
    *crickets chirping*

  • bikemonkey says:

    I doubt that data are sufficient to convey any true appreciation of what it means to bonk and how this differs from being (normally) exhausted from a hard workout, Isis.

  • natural cynic says:

    Both animal and human studies back in the 70's showed that muscle and liver glycogen were almost completely depleted at exhaustion. As is well over 90%. The level of exercise that can then be maintained at glycogen depletion theoretically will diminish, even though fat stores are still available. There is an old saying in exercise physiology that "fat needs to burn in a carbohydrate flame". What this means metabolically is that carbohydrate is necessary to replenish Krebs Cycle intermediates [oxalacetate is not 100% regenerated]. When no more carbohydrates are available, the body then has to depend on an insufficient supply of free amino acids to restock the TCA Cycle intermediates.
    This significantly lowers the amount of ATP that can be produced per volume of mitochondria which decreases force production which is picked up by the proprioceptive nerves which is like Scotty telling Capt. Kirk that "the drive canna' give ya more, things are gonna blow, I'll hafta shut her down". Other factors may also be involved such as nerve exhaustion [less likely], physical microdamge to the muscle fibers upsetting membrane integrity leading to inflammation; and hypoglycemia - blood glucose insufficiently feeds the brain and certainly cannot replenish the muscles. There's got to be others that I forgot right now.

  • Richard Eis says:

    Cardio day??...how amusing...I do 40 minutes everyday of fast walking as part of my daily life.
    I work out for an hour and a half at least with weights. Any less and i'm not tired, and i'm not exactly superman. Most of it is to counter a very sedentary job.

  • katie says:

    Heh...so that's what it's called. I've hit the "bonk" after 50ish minutes of fast jogging, and it seems to be a result of not eating soon enough before heading out. For me, at least, its a total shut-down: on the ground, head between the knees, and no sign of being able to walk normally without some sort of sugar.
    I think the problem with the whole exercise to lose weight thing is that we overestimate how many calories exercise burns, and underestimate how many calories we eat. And I really find that exercise greatly increases my appetite. You just really need to be aware of what you're burning, and what you're eating.

  • Right on! This type of article is over-the-top sensationalism intended solely to be controversial and thus sell magazines. The problem is that it is full of faulty science and, in some cases, downright wrong information. Worse, it sends the absolutely wrong message to the general public. I've posted a research-based response on my blog, http://www.workout911.com. Spread the word...
    Thanks,
    Brad

  • Anonymous says:

    Increasing your exercise won't make you lose weight if you correspondingly increase your food intake. At best you're just maintaining your original weight despite increased exercise. many people 'reward' themselves for sticking to an exercise regimen by pigging out more. It's not rocket science, folks.

  • gillt says:

    bonking or the gorilla on your back syndrome also has a psychological component: depression and hopelessness.
    Marathoners are very aware of it. It typically hits somewhere between mile 18 and 22, depending on the person.

  • bikemonkey says:

    gillt, that is 'cracking' not bonking.

  • gillt says:

    I'v been running marathons for 5 years and never heard of hitting the wall referred to as cracking.

  • bikemonkey says:

    gillt, it is unsurprising to me that marathoners don't know what they are talking about.
    I am familiar with descriptions of hitting the wall, mile 18-22. As you say, it is most frequently described as psychological accompanied by a description of a later recovery to finish the race. Sounds like cracking to me.
    bonking does not have this volitional or "psychological" component to it and is not recoverable absent consumption of calories or a VERY long, multiple hour rest interval.

  • Jen says:

    I've run marathons as well as done double-century bike rides. I'm familiar with both hitting the wall and bonking. To me they feel different. Hitting the wall feels much worse to me. When I bonk on a bike, I feel really really crappy, wanna throw up, dizzy, can't talk coherently, but I'm not actually in muscular pain. When I've hit the wall, it was the above in addition to my muscles cramping. Maybe it's just me.

  • bikemonkey says:

    I am not suggesting one is better or worse than the other.
    When I've hit the wall, it was the above in addition to my muscles cramping.
    the question is, is it a downward spiral from here until and unless you get food items in you? or do you start to feel better after a couple more miles? The latter points toward "crack" the former points toward "bonk". As I've said, most marathoners I talk to as having experienced the wall say that they eventually perk up, get through it and finish feeling somewhat better.

  • Brendan says:

    I read the time article. The man clearly doesn't understand exercize or medical research. One study (or even two or three) doesn't change the medical paradigm. If you follow any medical research, you realize studies like the ones cited by the author need follow up research and deeper analysis. These studies may in fact be on to something, but chances are it isn't what he thinks it is. More likely, they point to the problems faced by people who are just starting an exercize program. People who probably aren't doing very rigorous exercize. As a former athlete, I know that running over an hour five days a week (as part of my training), kept me slim (even after I stopped competing). Yes it made me hungry and I ate more, but my body needed the energy (yet I still lost weight). I have never really watched what i eat. The way I was trained was to eat what you crave as long as its real food, in order to build muscle and energy. But I know, even as I enter my late thirties, 45-60 minute jogs (4-5 days a week alternated with visits to the boxing gym) combined with weight training keep me in pretty good shape. And I always feed my appetite.

  • Kyle says:

    You are all morons. Losing weight is simply a combination of a dietary adjustment and massive tissue damage. In other words, reduce your carb intake, increase protein and fat, and engage in some brutally hard weightlifting. It takes days to recover from this kind of exercise and your metabolism will be elevated the entire time. Low intensity running, biking &c blows because it is so much less stressful (it is only the icing on the cake).

  • Gabe says:

    i bonked on my first 75 mile ride, which was in 90 degree sun, and i will never forget the torment of migraines occurring simultaneously all over my body. the feeling of cycling with muscles that became binary. the utter humbling weakness that wasn't a variant of my normal strength, but an entirely different physiological state.
    but i'm a glutton for punishment and smile even typing this.
    i've fought weight battles since i was 10, non-stop. the TIME quote makes me very very irritated, but i'm not terribly surprised. If someone wants to lose weight and get fit, they need to go WAY past TIME magazine

  • Gardenqueen says:

    Thank you for this. I read that article and it just didn't make sense to me. This does.

  • Hilary PhD says:

    The notion that you need to hit the wall, crack or bonk (in the US sense - the British meaning is entirely different) to lose weight is just plain daft and I can't believe it's being put forward here. I'm not saying the Time article is good but you're just as extreme in the opposite direction.
    Much more moderate exercise regimes can help people achieve negative energy balance and weight loss - all that's needed is a bit of control over calorie intake as well. I agree with JLowe and Kyle that weight training's as valuable as cardio, for the reasons they give but also because of the relatively high RESTING energy demand of lean muscle tissue - so any gain in muscle means burning more calories during the 23 or so hours when you're not exercising as well as the one or two when you are.

  • Garth says:

    Read 'Good Calories, Bad Calories' by Gary Taubes. Losing weight has less to do with exercise and more to do with what you eat. Cut the grain and sugar out of your diet and you'll lose weight with a moderate amount of exercise. Short, intense workouts are better. Check out http://www.crossfit.com for more details.
    When I think of bonking, I have a whole other exercise in mind that's a lot more fun 🙂

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