Debunking Time Magazine's "Why Exercise Won't Make You Thin"

TIME Magazine dropped a bomb shell article last week called, "Why Exercise Won't Make You Thin". This piece has ignited discussions and debates in blogospheres, talk shows and water coolers alike. I'm hoping to accomplish 2 goals with this entry:

1. Briefly explain why this fluff piece belongs in a magazine that features Jon and Kate (whoever they are), Octomom, and the stars from that literary-turned-box-office disaster, "Twilight."
2. Set the record straight about exercise and fat loss once and for all (for now, anyway).

In my mind there are a handful of crucial pitfalls the media tend to fall victim to when reporting on matters of health/fitness/nutrition:

1. The use of anecdotal evidence to support claims.
2. The haphazard use of blanket statements and universal qualifiers.
3. Keeping things vague in order to support said claims.
4. Eliminating the nuisance of fact checking.

In summary, the article essentially claims that exercise won't help you lose weight, and may in fact be responsible for people GAINING weight. Hmmm... The author, John Cloud (ooh the irony in that surname) goes on an anecdotally-based tirade, side-stepping contradictory evidence and common sense on route to his perplexing hypothesis.

Instead of droning on about the shortcomings of this article, I'm going to dole out some point-form bits about exercise and fat loss, hopefully undoing some of the misinformation that John "head in the" Cloud has created.

Exercise and Fat Loss: The Facts!

• Everybody should exercise for the health benefits first and foremost - there is no debate here - exercise is good for you. (In fairness, this is touched on in the article).
• Exercise in the absence of healthy eating and calorie control will not be very effective for fat loss.
• The term "exercise" is extremely broad in its definition, and hence we need to specify what kind of "exercise" we are talking about in order to draw a conclusion about its efficacy. I think we can all agree that there is a pretty substantial difference between walking on a treadmill at 2.3 mph, and doing barbell complexes and HIIT (high intensity interval training). This is where John Cloud looks to have graduated from the Gary Taubes school of ambiguity.
• Type (resistance vs. cardio), duration, intensity, frequency - these all have varying impacts on muscle tissue development, hormonal response, calorie expenditure, and henceforth the ability to burn fat.
• The familiar rhetoric that "overweight people eat no more, or exercise no less, than thin people" needs to be scrutinized, as obese people tend to underreport food intake, and over report physical activity.
• In the meta-analyses (compilation of studies) regarding exercise and weight loss, exercise typically has a "modest" effect on weight loss. Again, it's not going to do much in the absence of dietary change. Please note that "modest" does not mean "useless" or "counterproductive" or "a waste of time".
• On studies that have a diet only, exercise only, and exercise plus diet groups, the exercise plus diet groups (with scant exception) come out on top when it comes to weight/fat loss. Diet only, almost always beats out exercise only.
• One very well conducted 12 week study by Kramer et. al., which included both aerobic, strength training, and a dietary control, showed the following results. Fat mass losses - diet only: 6.7kg, diet/cardio: 7kg, diet/cardio/resistance: 10kg. Most noteworthy - the D+C+R group lost almost no lean tissue whatsoever, whereas the diet only group lost almost 3kg worth of lean tissue.
• Putting on and saving muscle tissue will have a lasting impact on your body's ability to lose fat. Plus you will look much better.
• Exercise becomes more important once you have lost the weight. Exercise should be a central strategy in preventing a re-gain.
• Pertaining to the above, the National Weight Loss Registry (which tracks those who have lost and kept off at least 30 lbs), shows that high levels of physical activity are a primary predictor of success.

What About Exercise and Hunger?

Does exercise cause people to eat more? Before we even get into the science, let's apply a little common sense here. Going to Starbucks for an oat fudge bar, and a caramel macchiato after you walk on the treadmill for 20 minutes WON'T GET YOU ANYWHERE.

Many people are under the delusion that they can eat more if they are active. Again, these people don't tend to lose fat. Dietary restraint is needed whether you are exercising a bit, a lot, or not at all. People who get this don't deliberately sabotage their efforts by indulging in sugar/fat/salt bombs. And guess what? They see results.

Insofar as exercise compelling us to eat more and crave junk? Not very convincing when you comb the literature. In fact, there are a great deal of studies that show exercise DOES NOT make you hungrier, and/or lead to eating above and beyond what you've burned.

Of course, there are those who are more susceptible to overeating in response to exercise (the so-termed "overcompensators"), and women in particular have more of a tendency towards this. But again, it comes down to a little restraint and common sense.

Moreover, research has also shown that athletes and lean people experience more of an increased appetite in response to exercise than do overweight individuals.

And further still, timing also has a lot to do with hunger and exercise as well. Another dose of... you guessed it, common sense! Don't go too long without eating before you exercise or you will be very hungry afterwards. Genius.

There are references below demonstrating that exercise does not cause overeating, but here is a quote from a noted researcher on the subject, C. Alan Titchenal:

Energy intake in humans is generally increased or unchanged in response to exercise. When energy intake increases in response to exercise it is usually below energy expenditure, resulting in negative energy balance and loss of bodyweight and fat. Thus, if energy intake is expressed relative to energy expenditure, appetite is usually reduced by exercise."

Don't Jump

I think this sort of issue needs to be addressed, as it only serves to inundate the public with half-truths and mistruths. I've scanned a few discussion boards on the topic and a typical response will read something like this:

OMGTHISISSOFREAKINGTRU! I werkout like all teh tyme and I'm not loosing any wait. I think I'll just do teh master clenz and stop going to teh gym FTW."

I'm all in favour of questioning conventional wisdom, but you must look at the totality of the evidence and adjust to your specific situation.

Next up: How to properly maximize exercise in a fat loss plan.

References:

1. Franz MJ, VanWormer JJ, Crain AL, Boucher JL, Histon T, Caplan W, Bowman JD, Pronk NP. Weight-loss outcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum 1-year follow-up. J Am Diet Assoc 107:1755 -1767, 2007


2. McGuire, M.T., Wing, R.R., Klem, M.L., Lang, W. and Hill, J.O. (1999). What predicts weight regain in a group of successful weight losers? Journal of Consulting and Clinical Psychology, 67(2), 177-185.


3. Blundell JE, cross talk between physical activity and appetite control: does physical activity stimulate appetite? Proc Nutr Soc, 62, 651-661. 2003


4. Donahoo WT, Variability in energy expenditure and its components. Curr Op Clin Nutr Metab. 7: 599-605. 2004.


5. Titchenal A., Exercise and Food Intake: what is the relationship? Sports Med, 6: 135-145. 1988


6. Yoshioka M, Impact of high-intensity exercise on energy expenditure, lipid oxidation and body fatness. Int J Obes. 25, 332-339. 2001


7. King NA, et al, Individual variability following 12 weeks of supervised exercise: Identification and characterization of compensation for exercise-induced weight loss. Int J Obes, 32, 177-184, 2008.


8. King NA, effects of exercise on appetite control: Implications for energy balance. Med Sci Sport Exer, 29(8): 1076-1089. 1997


9. King, NA, The relationship between physical activity and food intake. 57: 77-84. 1998.


10. Lluch A, Exercise enhances palatability of food, but does not increase food consumption, in lean restrained females. Int J Obes, 21: supp a129.Melzer K., effects of physical activity on food intake. Clin Nutr, 24: 885-895. 2005


11. Slentz CA. Effects of the amount of exercise on body weight, body composition, and measures of central obesity. Arch Intern Med. 164: 31-39. 2004


12. Ballard TP, Melby CL, Camus H, Cianciulli M, Pitts J, Schmidt S, Hickey MS. Effect of resistance exercise, with or without carbohydrate supplementation, on plasma ghrelin concentrations and postexercise hunger and food intake. Metabolism. 2009 Jun 2.


13. Dermott M, McDaniel JL, Weiss EP, Tomazic TJ, Mattfeldt-Beman M J Nutr Elder. Is physical activity associated with appetite? A survey of long-term care residents. 2009 Jan-Mar;28(1):72-80.