The first two or three paragraphs of this post aren’t going to sound like they have much to do with weight loss, but bear with me.
In October, I ran in a 3K (1.86-mile) “fun run” at my workplace, and was shocked to have to struggle to attain 8-minute miles. This is about a minute per mile slower than the last time I did the run, a few years ago, and that previous performance was itself much worse than a run a few years earlier. I no longer attempt to play competitive sports or to maintain a very high level of fitness, but this dismal performance convinced me that my modest level of exercise — a 20- to 40-mile bike ride or a 4-mile jog each weekend, a couple of one-hour medium-intensity exercise sessions during the week, and an occasional unusual effort (such as a 100-mile bike ride) — was not enough to keep my body at a level of fitness that I consider acceptable.
So after that run in October, I set some running goals: 200 meters in 31 seconds, 400m meters in der 64 seconds, and a mile in 6 minutes. (These are not athlete goals, but they are decent middle-aged-guy-with-a-bad-knee goals, and I make no apology for them). Around the end of October, I started going to the track 5 or 6 days per week, for an hour per workout. I started with the 200m goal. I alternated high-intensity workouts with lower-intensity workouts. All workouts start with 20 minutes of warmup, gradually building in intensity: skips, side-skips, butt-kicks, , a couple of active (non-stationary) stretching exercises, leg swings, high-knee running, backward shuffle, backward run, “karaokas” (a sort of sideways footwork drill), straight-leg bounds, and finally six or seven “accelerations”, accelerating from stationary to high speed over a distance of about 30 meters. After the 20-minute warmup, I do the heart of the program, which takes about 30 minutes. (The final ten minutes, I do “core” work such as crunches, and some stretching). A high-intensity workout might include running up stadium sections (about 12 seconds at very close to maximum effort, followed by a 20- to 30-second break, then repeat, multiple times), or all-out sprints of 60, 100, or 120 meters…or a variety of other exercises at close to maximum effort. Every week or so, I would do an all-out 200m to gauge my progress. My time dropped by about a second per week, and within about 6 weeks I had run my sub-31 and shifted my workouts to focus on the 400m goal (which I am still between 1 and 2 seconds from attaining, almost three months later, but that’s a different story).
So where does weight loss come in? I was shaving off pounds at about the same rate that I shaved off seconds in the 200m: I dropped from around 206 – 208 pounds at the end of October to under 200 in early December, and contined to lose weight more slowly after that, to my current weight of about 193-195. About twelve pounds of weight loss in as many weeks.
A few more relevant facts: (1) I’m quite tall, almost 6’4”, so my heavy-sounding 207 lb starting weight put me barely outside of the “normal” range by “body mass index” (BMI). My current weight of around 194 lbs is in the upper part of the “normal” range, although I’m still between 5 and 10 pounds heavier than I was in my early 30s, when I was playing a lot of competitive sports and was in pretty good shape. (2) During all of the time listed above, I have made no effort to control my eating. I still indulge my sweet tooth, often eating dessert at both lunch and dinner, and I pretty much eat what I want, when I want.
In short, there is no question in my mind that my weight loss is due to my exercise program, not to dietary changes. (And I guess I should mention that I had similar experiences back when I styled myself an athlete, putting on five pounds or so during the off-season and losing it once I started high-intensity work again). And yet, at around the time I was starting this program, articles were appearing like this
based on studies like this and this
that say that people, or at least most people, don’t lose weight from exercising alone, they have to do some sort of dietary control too; otherwise, the studies say, people increase their caloric intake to compensate for their exercise. So the studies say one thing, but my experience says another. What gives? Am I really unusual, responding to exercise in a way that differs from other people?
Well, I recently looked at the studies (or at least the abstracts for the studies) that claim that exercise doesn’t lead to weight loss, and noticed that the exercise intensity is quite low. For instance, one of the studies had people exercise for an hour at “55% of aerobic capacity”; a different study had people exercise at “70% of maximum heart rate.” These are about the same. Working out at this level, you definitely feel like you’re exercising, but it’s not a painful level of exertion. This is just a bit higher than the level at which I’m working during the second half of my warmup. So, what they are calling “exercise” for purposes of these studies is the level of exertion that I attain before I start exercising!
The theory that the weight loss/exercise researchers seem to be following is that, since a pretty low level of exertion maximizes the rate of fat-burning — at higher intensity your body switches to using glycogen — this low level must be optimal: if you don’t see weight loss from moderate exercise, you won’t see it from intense exercise. Well, that’s a reasonable theory, but it’s not necessarily right, and indeed from my experience I would have predicted that higher intensity exercise would be better, even though it doesn’t burn as much fat. As to how this could be, I don’t know. 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. I don’t have a physiological explanation, only the empirical observation that I, at least, lose weight (and quickly!) when I start doing high-intensity exercise, even if (even though) I make no effort to control my diet.
Doesn’t it seem like someone should study the effect of exercise above warmup intensity? At the very least, they should say “exercise at low or medium intensity doesn’t lead to weight loss,” rather than assuming, based on no data, that that is true of high-intensity exercise as well.