Exercise is great for your health, but it doesn’t do much for weight loss.
I’ve said it. Plenty of people I respect have said it. You might have said it. But based on recent experience, I’m not so sure it’s true.
That is, of course, what the research suggests. In my Science For Smart People speech, I mentioned a study in which middle-aged women were enrolled in a pretty intense aerobic exercise program: 45 minutes per session, five sessions per week. According to the published study, compliance was quite good. Women in the exercise group average 3.6 sessions per week. That works out to an average of 162 minutes per week.
And yet after a year, these women had lost an average of a whopping 4.4 pounds of body fat compared to a control group of women who didn’t exercise. Hardly a ringing endorsement of exercise as a fat-loss tool. (I mentioned the study in the speech because the researchers touted the results as proof that exercise is good for weight loss. Seriously? A year’s worth of effort to lose 4.4 pounds of body fat?)
The scientific literature is full of similar studies. People enroll in exercise programs, put in the time and effort, but lose very little weight.
And yet I have to balance that against my own experience. Exercise does seem to accelerate weight loss for me. I just proved that to myself again recently. Well, perhaps proved is too strong a word, so let’s just say I have n=1 evidence I find compelling.
For the past several years, my weight has generally hovered around the 200 mark. In the summer I’ll typically weigh 197 pounds or so, and in the winter I might weigh more like 202. I fattened myself up during the 2016 holiday season by indulging in too much good scotch and good food, but lost the extra bloat once I went back to my usual diet.
Then came the surgery in November. I didn’t think I’d gain any significant weight during the long recovery, but I did. A big part of that was diet. I’d been cut open, had bone shaved away, and had a torn tendon re-attached. I didn’t want to be in a catabolic state when my body was trying to rebuild damaged tissues. So I ate rather freely, including more potatoes and other starches I’d normally limit. My physical activity, of course, went down to zero after the surgery.
We don’t have a scale at home, so the first time I weighed myself was in January, when I went to the gym just to work my legs. The scale said I was at 213 pounds. Yikes.
I tightened up the diet, went back to limiting the carbs to somewhere in the 50-75 gram per day range, watched my portions, fasted until dinner two days per week, limited my alcohol consumption to two beers on Friday night, etc. Yeah, that should do it.
Six weeks ago, I went to the gym to work my legs and stepped on the scale. I was at 212 pounds.
What the f…? I tightened up my diet for nearly six weeks and lost one pound?! Well, that’s just awesome. At this rate, it will only take me until sometime in 2019 to be back to what I consider my normal weight.
When I was hitting the gym regularly and putting in farm-work sessions on weekends, that same diet kept me at or below 200 pounds. I wasn’t cleared yet for lifting weights or doing heavy outdoor work, so I made one additional change to my routine: I started diligently using the treadmill I bought myself after the surgery. This one:
For the past six weeks, I’ve been putting in hour-long walking sessions four or five nights per week. I actually find them quite pleasant. The treadmill has a little shelf to hold a tablet and a connection jack to built-in speakers. I watch documentaries on my iPad while walking (the latest is Wild Wild Country on Netflix) and the hour goes by quickly.
I had my final follow-up session with the surgeon a few days ago and finally got clearance to do full workouts at the gym again, with a few caveats: 1) start at half the weight I used to lift on all upper-body machines, 2) don’t go to a higher weight until I can do 15-20 reps with good form, and 3) don’t ignore pain and try to work through it.
Yeah, okay, I’m fine with those. I’ll turn 60 in November and have had my shoulder surgically repaired twice now, with a bicep surgery and a knee surgery tossed in for good measure. I shouldn’t expect to work out like a 25-year-old jock.
On Sunday, I went to the gym and worked my upper body for the first time in six months. The bad news is that I’m a lot weaker than before the surgery. I thought dropping to half the previous load would make each exercise seem ridiculously easy, but, uh, no. It was real work.
The good news is that when I stepped on the scale, I weighed 205 pounds. That means I’ve lost seven pounds in six weeks – on the same diet that previously produced a one-pound weight loss in a similar span. The only difference I can see is the time I’ve been putting in on the treadmill.
Keep in mind, I’m not suggesting it’s a simple matter of calorie math. In fact, the usual calorie math doesn’t account for it. The treadmill has a feature that displays how many calories you burn during a session based on your weight, the incline, the speed, the distance, etc. If the feature is accurate, I’m burning around 300 calories per session. At five sessions per week, that would translate to 1500 calories, or less than half a pound. But I’ve lost just over a pound per week.
Back in my low-fat, high-carb diet days, I jogged for lord-only-knows how many miles and spent countless hours on treadmills, but never lost any significant weight. If it were a simple matter of losing weight by burning calories through exercise, I should have gotten leaner. But I didn’t.
So why do I believe exercise is working as a fat-loss tool now, when it failed me before and has failed so many times in clinical research? I’m just spit-balling here, but I think it probably comes down to hormones.
To explain, I’ll quote from the Fat Head Kids book. In the chapter on why we get fat, we introduce Marty Metabolism, the chief engineer for the biological starship known as The Nautilus. Getting fat, we explain, is the result of Marty receiving commands delivered by chemical messengers called hormones:
Since Marty is under orders to store more fat, he’ll trigger the Get Hungry! program to make you eat more. But if that doesn’t work, he’ll slow down your metabolism to burn less fuel. Either way, you end up consuming more calories than you burn … The commands from hormones are so powerful, Marty can’t just ignore them.
Trying to lose weight by burning calories through exercise is just the flipside of trying to lose weight by eating a bit less. Both assume your body works like a simple bank account, with your weight determined by the simple math of deposits vs. withdrawals. Cut your calories by 500 per day, and by gosh, you’ll automatically lose half-a-pound per week and all that.
But of course, our bodies are nowhere near that simple. Marty has to be willing to go along with the plan. Otherwise, he’ll respond to that attempt at creating a calorie deficit by slowing your metabolism to match the lower food intake.
When I used to go jogging for miles, I was still eating a diet that commanded Marty not to burn away stored fat. So he didn’t. I suspect that in many of the studies on exercise and weight loss (or lack thereof), the subjects were also consuming a diet that worked against burning away stored fat.
But suppose we switch to a diet that tells Marty, through a change in hormonal signals, that it’s perfectly fine to tap the fat stores. Now eating less works. Now exercising works.
And of course, the right kind of exercise also affects the hormonal balance. It improves insulin sensitivity, to name just one benefit. To name another, I’ll quote from the excellent book Primal Endurance, by Mark Sisson and Brad Kearns:
Exercise not only increases the size and number of mitochondria, but also makes them more efficient by increasing the number of oxidative enzymes found in mitochondria. These enzymes improve metabolic function of your skeletal muscles, boosting fat and carbohydrate breakdown for fuel, and speeding energy formation from ATP.
Dr. Bill Lagakos, author of the poor, misunderstood calorie, has also written about how walking lowers fasting glucose and fasting insulin levels. (I believe you have to be a Patreon of his site to read the full article. If you’re not a Patreon, I’d urge you to become one. He puts out a heckuva lot of good material.)
Exercise suppresses insulin via sympathetic nervous system. This doesn’t matter because a contracting muscle, or rather the contraction itself, recruits GLUT4 to the surface of contracting muscle to suck up glucose, to fuel the contraction. It doesn’t need insulin to do this. Glucose-lowering this way also contributes to reduced need for insulin. This is a very healthy thing.
As Sisson and Kearns emphasize in their book, crappy foods can easily cancel out those benefits. That’s why there’s an entire section on diet in what’s otherwise an exercise book.
But if you don’t cancel them out, the benefits are real. I’m pretty sure that’s why I’m no longer stalled on losing the post-surgery fat.
Add it all up, and I’m not sure we’re doing anyone any favors by insisting exercise doesn’t do much for weight loss. Combined with a diet that creates a favorable hormonal mix, perhaps it does. It sure seems to be helping in my case.
But that’s my n=1 experience. I’d like to hear how exercise has or hasn’t worked for the rest of you.
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