Sunday, August 30, 2009

Can exercise make you thin? Or maybe it can make you fat....?

Well of course, this would seem an absurd question to most of us, but not so it seems to John Cloud from Time Magazine in the US whose latest article has garnered all kinds of attention for it's rather tilted stance on the use of exercise as an adjunct to weight loss. Now, if we tried to correct every oversight or technicality on the internet we would be here all day, every day, but we couldn't let this one slide and here is why.

This reply was inspired by a friends somewhat desperate email to me about the article that appeared recently in Time magazine entitled Why Exercise won't make you thin'. My friend was horrified, all of a sudden she was counting her 'wasted hours' at the gym and spiraling into despair about what the hell she is actually meant to do to lose weight. I don't blame her, frankly the sheer volume of information on the internet is so vast it is hard to actually comprehend. Therefore, if you want to get your piece noticed then you have to have an angle, and John Cloud the author of the Time magazine piece certainly picked a good angle.

However, while he picked a good angle, his piece is a prime example of how to cherry pick research with strong selection biases (while Mr Cloud references the excellent Gary Taubes, I believe he might have missed the earlier chapters of Taubes book describing these) and glaring technical errors - even the old 'turn fat into muscle ' slipped into it. Of course, as this piece isn't a literature review and rather a more direct rebuttal, I have done similar and shown how easy it is to find research strongly contradicting this article.

On the first page of Mr Clouds article he quotes Eric Ravussin, Chair of Diabetes and Metabolism at Lousiana State university who comes out with a corker stating 'in general for weight loss, exercise is pretty useless' - nice one doc, but allow me to issue a rebuttal to that rather non-academic statement. You see first of all, the interpretation of that statement for the general public is that if someone wants to lose weight or is indeed overweight, then they shouldn't bother exercising. I disagree and I think that a review of literature tends to contradict Dr (?) Ravussin's statement.

In an academic review of available literature carried out in 2005 and published in the peer reviewed International journal of Obesity, Curioni and Lurenco (2005) stated that "diet associated with exercise weight loss produced a 20% greater effect than diet alone and 20% greater sustained weight loss after 1 year". So, score one for exercise. However, there is a more disturbing trend as highlighted in research from the Journal of the American Dietetic Association who found that although dieting alone produced results comparable with diet and exercise over the course of a year, those who didn't exercise were highly likely to regain their weight. This trend seems to be so evident in the research that it is a wonder anyone could reach the astounding conclusion that exercise might actually make you fatter, as Mr Cloud ventures in his article. It would in fact be easy to write an entire book simply full of reasons why you should exercise, particularly if you are trying to lose weight. For example, research has also found that adding resistance training to a diet intervention, while it made no significant difference to weight loss (wait for it...) did make a significant impact on the amount of lean muscle lost (Bryner at al 1999, Geliebtner et al 1997). It also found that in women between 35-50 (presumably a target market for this kind of piece) that exercise and physical activity can make a significant impact on metabolic rate (the amount of calories you burn to keep everything in the body ticking over nicely) and fat free mass (Gilliat-Wimberly et al 2001). It isn't just the girls either, guys too need to keep training, as if they maintain activity as they age then they also are able to maintain their metabolic rate (Van Pelt et al 2001), so in fact NOT exercising as Mr Cloud suggests would seem to be a recipe for gaining fat as you age rather than losing it.

There is no secret to this research, you can find it yourself, go to Google Scholar and type in 'exercise, weight loss, review' as a search term and most of these studies are near the top of the page. Much like weight loss itself, this isn't a complex thing to undertake, but it requires effort, time, patience, and a modicom of knowledge on where to go to get the right information.

Looking at the research I find Ravussins comments even more surprising, particularly from a chair of diabetes, given the strong ties between diabetes and insulin resistance and the overwhelming evidence to support exercise as an intervention in Type 2 or non-insulin dependent diabetes. Here is what the International Journal of Sports Medicine have to say on the matter "we conclude that physical training plays an important if not essential role in the treatment and prevention of insulin sensitivity" (emphasis added by this author) they also outline that the regulation of hepatic glucose output is improved by physical training, which is of particular benefit to NIDDM (Borqhouts & Keiser 2000). I could go on and indeed I will as i am unsure of Ravussins motivations for his comments, however, I will let the data and evidence speak for itself. Here is paraphrased (I'd love to have quoted the entire abstract but space is becoming a consideration) what the University of Texas had to say on the topic "the protective effects of physical exercise are strongest for those at highest risk of developing NIDDM, there are several important adaptations to exercise training that may be beneficial in the prevention and treatment of insulin resistance, impaired glucose tolerance, and NIDDM" (Ivy 1997). I am not sure that the rather dismissive absolutism with which Ravussin states that exercise is 'pretty useless' does justice to his rather magniloquent title. Is this the message that he is sending his undergraduate students before they go out into the wide world of working with people with insulin resistance, metabolic syndrome, and NIDDM? Let us hope not.

Now, this is turning into a long article, but there are a couple more points to be made. Firstly, in a literature review, such as those referenced above you provide a critique of the evidence for and against. This rarely happens in journalistic articles for two reasons namely 1) it makes for rather dry reading (as I am sure you are finding) and 2) it doesn't give the 'quick fix' hook that the public are looking for and that sells magazines. I don't want to get into a diatribe here about what you should and should not do to lose weight, but merely try and provide some balance to the original article. Secondly, as we are in rebuttal territory of some of the quoted research in the Time article, a central theme is that exercising will encourage you to eat more and indeed to choose worse food choices. Again, a look at the literature doesn't tend to support this conclusion as Bellisle (1999) states in the Journal of Public Health "there is no scientific evidence that exercise increases appetite, but very intense exercise may suppress it transitorily" in contradiction to Mr cloud who suggests that 'intense' exercise will cause you to eat more. Bellisle goes on to point out (along with several other studies on the topic) that our social, psychological, and emotional habits all play a more significant role in how we go about selecting our food after exercising and in general, a sentiment echoed recently by Booth et al (2009) in the Nutrition Review Journal.

So, what should the take home message be for those of you still a little confused about what you should and should not be doing?

Well firstly, the benefits of a structured, progressive programme of exercise - including resistance training, not simply aerobic work - are so wide ranging and obvious that everyone should be encouraged to do it. While research on the specific effects of exercise as a weight loss modality may have proved underwhelming in some of the research (generally adding aerobic training to diets) for creating a strong additional effect, it is VERY evident that exercise plays a large role in keeping weight loss permanent and in creating long-term success. Pavlou et al (1989) concluded that dietary treatment alone had no effect at 18 month or 36 month periods and that all NON-exercise groups regained weight lost, in stark contrast to the exercise intervention where those who stuck at it managed to maintain weight lost. This is strong evidence indeed of the importance of exercise as part of a weight loss programme and another pretty firm nail in the coffin for naysayers such as Mr Cloud of Time Magazine. There is also good evidence that resistance training for example can play a strong role in the maintenance of fat free mass both in relation to dieting and ageing.

Of course though, results don't come by accident, they come through effort, but unfortunately it seems that our current trend is to go in search of the next quick fix solution rather than face the hard truth about what we need to do. This would explain why the public would love to read an article telling them exercise is a waste of time, I cannot imagine an article saying "weight loss takes work" would be anywhere near as popular. However, it would be a more truthful sentiment. The notion that 'walking home with the groceries' is 'just as effective' is laughable and in fact against all the long-established truths that exercise must be progressive and overload the body if it is to be successful.

As for Mr Cloud himself who has 'never been overweight' apparently, yet by his own admission has a gut that hangs over his belt? Well according to his article, his own 'intense' regime doesn't even leave him with enough energy to shop or cook, leaving him no choice but to go to Pizza Hut and do nothing whatsoever for the rest of the day. Indeed, he states that perhaps if he didn't train so hard, he might have the energy to take the stairs more often! He must certainly train hard if that is the case, harder than anyone I know, or could it be his lack of energy is linked to something other than his exercise, such as a lack of effort or education in how to eat correctly? Einstein first said that the definition of insanity is to repeat the same exercise over and over and to expect different results, a lesson Mr Cloud has yet to learn it would seem

Sure, you can't compensate for a terrible diet through a few sessions a week in the gym - although you can lessen the effects and improve other markers of fitness aside from weight, such as improving insulin sensitivity, increasing strength, improving mobility, and alleviating the effects of depression, to name but a few. Underneath all the hyperbole, this is the message that the article is trying to convey- that weight loss begins with good nutritional practices and can be enhanced through increasing overall activity levels, although the effectiveness of different types of exercise can be widely variable depending on a huge number of factors. However, the overall benefits of a structured exercise programme far outweigh any of the possible negatives, and the evidence doesn't concur with the original authors skewed perspective on it, nor does it account for his own personal failure to achieve the physique we presume he is after. The fact is that rather like Mr Cloud, many people undermine their efforts either through a lack of education or a lack of effort, some just don't train hard enough or often enough, while others place too much stock in the effect that 20 minutes of slow jogging is going to have on their weight loss. While it is true that heavier people already burn more calories simply through their weight - this cannot be compared to expending energy in a form that will actually stimulate adaptation and change within the body. There is a fundamental difference.

It would certainly seem to be putting the cart well before the horse to try and suggest that exercise is of no use in the efforts to help obesity and may even make people eat worse and get fatter? Last time I checked the global obesity crisis was not caused by over-exercising or by an epidemic of overeating and inactivity brought on by intense physical exercise. While the notion that you shouldn't be doing any exercise apart from walking the odd flight of stairs or carrying the shopping home may appeal to modern societies quick-fix nature, everything else in our evolution and in our sports science would scream that this is nothing more than journalistic quackery and hyperbole. My advice, if you want to know the truth about getting in shape, start by listening to someone who is, rather than someone who by their own admittance isn't.


Booth et al (2009) Environmental and Societal Factors Affect Food Choice and Physical Activity: Rationale, Influences, and Leverage Points. Nutrition Reviews Volume 59 Issue 3, Pages S21 - S36

Bellisle (1999) Food choice, appetite and physical activity. Public Health Nutrition: 2(3a), 357 – 361

Blair (1993) Evidence for Success of Exercise in Weight Loss and Control. Ann Int Med. 1 October 119(7): 2, 702-706

Borqhouts & Keizer (2000) Exercise and insulin sensitivity : A review. International journal of sports medicine. 2000, vol. 21, no1, pp. 1-12 (130 ref.)

Bryner at al (1999) Effects of resistance vs. aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate. J Am Coll Nutr. 1999 Apr;18(2):115-21.

Curioni & Lourenco (2005) Long-term weight loss after diet and exercise: a systematic review. International Journal of Obesity 29, 1168–1174.

Garrow & Summerbell (1995) Meta-analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects. Eur-J-Clin-Nutr. 1995 Jan; 49(1): 1-10

Geliebtner et al (1997) Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects. Am J Clin Nutr. 1997 Sep;66(3):557-63.

Ivy (1997) Role of exercise training in the prevention and treatment of insulin resistance and non-insulin-dependent diabetes mellitus. Sports Med. 1997 Nov;24(5):321-36.

Pavlou et al (1989) Exercise as an adjunct to weight loss and maintenance in moderately obese subjects. Am J Clin Nutr 49(5): 1115

Skender at al (1996) Comparison of 2-Year Weight Loss Trends in Behavioral Treatments of Obesity: Diet, Exercise, and Combination Interventions. J Am Diet Assoc. 1996; 96:342-346.

Van Pelt et al (2001) Age-related decline in RMR in physically active men: relation to exercise volume and energy intake. Am J Physiol Endocrinol Metab. 2001 Sep;281(3):E633-9

Wallberg-Henriksson et al (1998) Exercise in the management of non-insulin-dependent diabetes mellitus. Sports Med. 1998 Jan;25(1):25-35.

1 comment:

Naveed said...

Fitness and Health is basic part of life we must care for it therefore i read the article and found the nice tips which are useful for us

i used this post at night when i think about my friends and family so i really thankful for providing very knowledgeable information for further help

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