So let’s continue picking apart the Time Magazine article:

If you missed part 1 of this San Diego sports doctor’s response to the Time Magazine article “Why exercise won’t make you thin”, you can find it on our sports medicine blog.

“Yes, although the muscle-fat relationship is often misunderstood. According to calculations published in the journal Obesity Research by a Columbia University team in 2001, a pound of muscle burns approximately six calories a day in a resting body, compared with the two calories that a pound of fat burns. Which means that after you work out hard enough to convert, say, 10 lb. of fat to muscle — a major achievement — you would be able to eat only an extra 40 calories per day, about the amount in a teaspoon of butter, before beginning to gain weight. Good luck with that.”

While Mr Cloud is technically correct about the 40 calorie difference between 10 pounds of muscle and 10 pound of fat at rest, he doesn’t take into consideration two important calculations – the initial energy expenditure someone would need (that means exercise) to lose 10 pounds of fat while building 10 pounds of muscle and the daily difference that the extra ten pounds of muscle adds when the muscle is active during exercise. The study Mr Cloud quotes talks about the energy expenditure difference when at rest (sleeping, sitting, etc) but there may be a noticable increase in energy expenditure once you start using that added 10 pounds of muscle during daily movement or exercise depending on your view of the research. A study published in the Journal of Applied Physiology from the University of Alabama in 2000 looked at the effects of 26 week resistance training on older adults found that even after correcting for the energy expenditure during the resistance workout, there was still an increase in the total daily energy expenditure of about 178 extra calories per day.

Mr Cloud continues…”All this helps explain why our herculean exercise over the past 30 years — all the personal trainers, StairMasters and VersaClimbers; all the Pilates classes and yoga retreats and fat camps — hasn’t made us thinner. After we exercise, we often crave sugary calories like those in muffins or in “sports” drinks like Gatorade. A standard 20-oz. bottle of Gatorade contains 130 calories. If you’re hot and thirsty after a 20-minute run in summer heat, it’s easy to guzzle that bottle in 20 seconds, in which case the caloric expenditure and the caloric intake are probably a wash. From a weight-loss perspective, you would have been better off sitting on the sofa knitting.”

One rough rule of thumb is based on a 2004 study on the energy expenditure of walking and running published in the journal Medicine & Science in Sports and Exercise which found the total number of calories burned from walking 1 mile was equal to 0.53 x the person’s body weight (in pounds) and the total number of calories used during running was approximately 0.75 x the person’s body weight (in pounds). So for the above example of a 20 minute run, if we assume a slow jog at 10 minute per mile pace (or 2 miles in 20 minutes), a 155 pound person would still burn (0.75 x 155)

There are several readily available activity-calorie guides at http://www.nutristrategy.com/activitylist3.htm and http://www.healthdiscovery.net/links/calculators/calorie_calculator.htm that calculate calories burned for various exercises and exercise intensities. Looking at values from the above on-line calorie guides, running 20 minutes at a fast jog (2 miles at a 10 minute per mile pace) would require about (704 calories/ hr * 0.333 of an hour) 234.6 calories of energy expenditure in a 155 lbs person. In a 190 lbs person, that 2 mile jog would burn about 287 calories – even if we took a light weight 130 pound Kenyan marathoner on a really, really slow day for him, we’d still be looking at a caloric burn of roughly 196 calories, still more that the 130 calorie Gatorade that the author blames for adding the extra poundage to Americans.

Yes, obviously chugging the 130 calorie Gatorade wouldn’t result in as much of a calorie-deficient from the 20 mintues of exercise that just drinking plain water, but that short time duration of exercise is also why sports medicine societies like the American College of Sports Medicine don’t start recommending a carbohydrate and electrolyte sports drink unless the exercise is an hour or more.

How about the psychology of self-control? – Or the comment that self control is like a muscle that gets weaker each time you use it? There is actually a lot of interesting published research on the science of “self-control” behavior as it relates to a lot of different areas; diet, addiction, criminal activity, etc. The study that the Time Magazine article referred to appeared to find that in the group of test subjects that demonstrated diminishing “self-control” with exercise or food selections may also have had a less intense sense or feeling of motivation towards reaching weight loss goals in comparison to the group of test subjects that did not exhibit a diminishing level of “self-control.” This finding may have more to do with the role of fitness and health professionals role in identifying and improving the level of motivation among weight loss and fitness clients. Some people approach exercise, fitness and weight loss with a negative attitude (like one patient of mine that commonly pointed out that “diet” was a painful four letter word, just “die” with a “t” added at the end. So the role of motivation towards any goal is paramount to success. Want to become an Olympic gold medalist? Want to be successful in the work place? Want to reach your goal of running a 5k, 10k, marathon or Ironman triathlon? Motivation is a key personality ingredient that can determines a person’s success with the goals they set for themselves and challenges that they face.

Memory recall of a recent meal may actually play a larger role in appetite suppression than previously thought. A series of studies published in 2008 by University of Birmingham’s School of Psychology looked at the effect of having test subjects recall what they ate just before their next meal or snack and found that the test group that did participate in the part of the study where they recalled what they ate for lunch actually ate less food for an afternoon snack. The research seemed to indicate that the phenomenon was time-dependent, meaning that the larger inhibitory effect was seen in test subjects that recalled their most recent meal rather than a meal from the previous day.

Is this the Homer Simpson theory? – could my one of my favorite shows have actually gotten it all wrong along with Time magazine? All those times that Homer J. Simpson daydreams of donuts, chocolate, Duff beer, etc were actually dietary mind control tricks acting to suppress his actual appetite? Well, according to this research, the memory effect only applies to food eaten that day. So you can think about what you had for lunch today and it will decrease your appetite for that later afternoon snack, but thinking about yesterdays lunch doesn’t have the same impact on appetitie control.

This concept of “appetite mind control” may seem like some pop psychology trick, but in fact may be related to the influence of the hormone gherlin, which influences not only the control of hunger, but also possibly cognitive function and learning ability. Animal studies have shown better performance on learning specific tasks for animals that are unfed versus those that have recently been fed, supposedly due to the effect of gherlin concentrations on the hippocampus portion of the brain. Which would explain the “Fat, happy rats don’t run mazes” theory…

I’ve had several people ask me if I felt that the writer wrote the article in this manner to be intentionally controversial. Overall, I think the Time Magazine writer didn’t intentionally try to misrepresent the research. I feel that he simply didn’t understand the research that he was attempting to use to support his theory in the article. He did manage to energize quite a response from the medical and fitness fields, however, based on the number of follow up blog posts and website articles that have been posted. Hopefully people look deeper into the issue and realize the importance of exercise not only for weight loss and weight mantenance, but for overall health

Related posts:

1. Does reading Time Magazine make you dumb? Part 1
2. Four weeks to a faster time trial for cyclists and triathletes
3. Caffeine reduces muscle soreness after cycling