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You heard it here first: Intense exercise can suppress appetite

This post is by Phil Price.

The New York Times recently ran an article entitled “How Exercise Can Help Us Eat Less,” which begins with this: “Strenuous exercise seems to dull the urge to eat afterward better than gentler workouts, several new studies show, adding to a growing body of science suggesting that intense exercise may have unique benefits.” The article is based on a couple of recent studies in which moderately overweight volunteers participated in different types of exercise, and had their food intake monitored at a subsequent meal.

The article also says “[The volunteers] also displayed significantly lower levels of the hormone ghrelin, which is known to stimulate appetite, and elevated levels of both blood lactate and blood sugar, which have been shown to lessen the drive to eat, after the most vigorous interval session than after the other workouts. And the appetite-suppressing effect of the highly intense intervals lingered into the next day, according to food diaries that the men completed. They consumed fewer calories during the subsequent 24 hours after the very intense 15-second intervals than after any of the other workouts.”

This does not surprise me: I’ve long been aware that my appetite is substantially depressed immediately after high-intensity exercise, and that even hours later I tend to be less hungry than after a less intense exercise session. (When I say “high-intensity exercise”  I mean an effort that brings my heart rate very close to its maximum, or, equivalently,  an intensity I cannot maintain for much more than 20-30 seconds; this is comparable to the maximum intensities in both of those studies.)

The article points out that the studies were very short-term, so they don’t show that in the long run the volunteers would lose weight if they continued to perform high-intensity workouts.  My guess, though, is that they would, or at least some of them would:  As I’ve noted in previous posts, when I add more high-intensity exercise to my exercise schedule  I tend to lose weight, and when I take some high-intensity exercise out of my schedule I tend to gain weight.  As I said in my 2010 post, I wasn’t prepared to make a claim on why high-intensity exercise affects my weight, but “Maybe high-intensity exercise doesn’t increase one’s appetite as much as low-intensity exercise does, or perhaps it causes a long-term increase in metabolic rate that lower-intensity exercise doesn’t cause.”  These studies suggest that that first supposition may well be true. Of course, the second might also be true: they aren’t mutually exclusive.

A few more things that I’ll say here, because commenters on those previous posts have often missed or misunderstood these points:

  1. My claim (in my previous posts on this subject) is that high-intensity exercise affects my body weight and body fat content, absent any conscious efforts to control my weight through diet or other means. Some other commenters have had the same experience. This does not mean it would have this affect for everybody.
  2. I do not claim that this fact has implications for “solving America’s obesity epidemic” or anything like that. I know I’m not unique in the effect of high-intensity exercise on weight, but I don’t know that it would work for most people. I do know that most people aren’t willing to do it.
  3. At least for me, the total amount of energy I expend during high-intensity exercise is not the cause of my weight loss: adding just a few 30-second high-intensity intervals per week has a noticeable effect, even though a single 30-second interval burns less than 10 Calories.

This post is by Phil Price

3 Comments

  1. Fernando says:

    Phil,

    A DAG of your causal theory would be a wonderful way to illustrate this post (see http://daft-pgm.org/ for a nice tool).

    It would also help focus the debate, and make clear what kind of causal model you have in mind in a succinct way.

  2. Matt says:

    Not a huge expert on this, but–I thought the conventional wisdom was that short, high intensity workouts raise your normal at-rest metabolism much more than long, lower intensity workouts do. So maybe the “perhaps” qualifier is unnecessary.

    • Anonymous says:

      And like most* “conventional wisdom”, it’s false.

      * This statistic coming from the “90% of statistics are fake” department.