A friend of mine asked me a week ago, "So, how important do you really think exercise is for weight loss?" I gave a rambly off-the-cuff answer, but I wasn't satisfied with it. Let me try again.
Research data does exist about the subject. But the kind of data that's out there is not the sort that can be translated into advice for everyone.
Some of it reports a relationship between exercise and immediate weight loss; some of it reports a relationship between exercise and long-term weight maintenance. Some of it compares cardiovascular-type exercise to resistance-type exercise. Some of it reports what happens when totally sedentary people take up very minimal exercise; some of it reports what happens when people who move around during their normal lives introduce sessions of intense exercise; some of it reports what happens when people who already exercise in sessions add more sessions. Some work studies people who are generally healthy, some work studies people who are ill or frail. Clearly not all of the results are relevant to each person.
And then, what comes out in the headlines isn't necessarily what the researchers were studying. Check out this apparently decent article in The Guardian: "Why exercise won't make you thin." The article reports:
But if you go to the journal article abstract, you will find no mention of weight loss. The study's authors apparently felt that the really important result was the relationship between exercise and cardiorespiratory fitness. (There is one.)
In what has become a defining experiment at the University of Louisiana, led by Dr Timothy Church, hundreds of overweight women were put on exercise regimes for a six-month period. Some worked out for 72 minutes each week, some for 136 minutes, and some for 194. A fourth group kept to their normal daily routine with no additional exercise.
Against all the laws of natural justice, at the end of the study, there was no significant difference in weight loss between those who had exercised – some of them for several days a week – and those who hadn't. (Church doesn't record whether he told the women who he'd had training for three and half hours a week, or whether he was wearing protective clothing when he did.) Some of the women even gained weight.
Finally, the numbers are not really simple enough to be distilled into headlines without losing some subtlety. Let's say that "New study shows that X is superior to Y when it comes to losing weight." This may mean that the average weight loss in the X group was significantly more than the average weight loss in the Y group. Or it might mean that a greater percentage of the X group than of the Y group achieved some criterion for "success." But often there are some individuals in the Y group who outperformed individuals in the X group for some unknown reason. How do you know which group you would do better in? You don't, unless you try X and you try Y.
So: Most of what you read in the papers may as well be ignored as acted upon.
That being said, I am personally convinced of this:
Exercise is next to useless for weight loss. If there is an effect, it is so small as to be not worth the time and effort anyone puts into weight loss. If the only reason you want to exercise is to lose weight, don't bother. Seriously.
Why do you want to lose weight?
If any part of that is "Because I want to be healthier" --- or "stronger" --- or "able to do more things" --- or "longer-lived" ---
--- then exercise will give you that, EVEN IF YOU DO NOT LOSE ANY WEIGHT AT ALL.
I can't stress this one enough.
Mark told me about a paper that he saw presented at a conference that, while I cannot link to it, will do for an illustration. The research subjects were overweight people who increased their exercise for the study. Rather than just presenting averages and standard deviations and the like, the presenter showed data for all the individuals. A few gained weight. Most lost very little weight or no weight. Some lost a significant amount of weight. But all of them increased their muscle mass, and all of them increased their lean-to-fat body ratio.
Yeah, some people will lose weight after they start exercising. Good for them. But why not just start with the assumption: "Exercise will probably not help me lose weight, but it will definitely make me healthier."
So fess up. If you are the sort to say you don't care so much about your appearance, but you want to lose weight because it's good for your health... well, if that's true then the only logical response is to get some exercise.
Or even if you DO care about your appearance, AND you want to lose weight because it's good for your health, then the only logical response is STILL to get some exercise.
"But wait," you might be saying. "I do only care about my health, but we all know that simply being obese is so very bad for my health, that if I stay obese I'm going to be unhealthy anyway. I should try to lose weight first, and if exercise won't help me lose weight or might even make it harder to lose weight, then it'll actually be standing in the way of better health."
Bzzt. Very, very little evidence exists for the assertion that being obese, alone, causes health problems. Correlation has been demonstrated. Causation, not so much.
Exercise will definitely make you healthier. Losing weight will not definitely make you healthier.
So. Let me distill this into a handy Q&A.
Q. I want to lose weight, so should I be getting regular exercise?
Q. If I want to GAIN weight, should I be getting regular exercise?
Q. Let's suppose I don't give a flying fig newton whether my weight goes up or down or stays the same. Should I be getting regular exercise?
A. Do I really have to answer that?
Q. Yes, just for the sake of completeness.
Q. That's what I thought you would say.
A. Glad to oblige.
Q. Okay, this is what I REALLY meant to say. I'm not getting regular exercise, and I'm not losing weight as fast as I want to. Will it help me lose weight if I get more exercise?
A. I can't be sure, but probably not.
Q. Is that bad news or good news?