TIME columnist John Cloud caused a minor furor in the blogosphere last August with the cover article “Why Exercise Won’t Make You Thin.” Within 24 hours fitness evangelists all over the Internet derided the article as irresponsible and inaccurate. And you may have had to do a little damage control with your participants.  

If you read the article closely, however, the author basically supported the title’s premise — exercise alone won’t make you thin. Unfortunately, many of those attempting to disprove Cloud’s assertion presented even more random support for their position and/or proved an entirely different point (that exercise is good for you)… unwittingly bolstering his article.  

Exercise by itself typically doesn’t help people lose more than a few pounds. The body has an amazing ability to maintain homeostasis, perfected over many millennia of evolution, despite increasing energy expenditure by a few hundred calories a day. In a nutshell, the body tells us to have a second helping (or a candy bar); and we do, so we don’t lose weight.  

Our October 7 Wellness Solutions column described how refreshing, indeed liberating, it can be for participants to hear the truth about changing behaviors (it’s hard, it’s easy to slip back, little changes won’t do). The exercise-will-make-you-thin fallacy is another case in point. It won’t, so don’t say it.  

For the vast majority of people, the only way to lose weight is to cut down on the number of calories consumed by paying careful attention to what, when, and how you eat. You can accelerate weight loss a bit with exercise, but if you don’t change your eating habits as well, the weight loss will be minimal. That’s the truth. 

But, as Paul Harvey used to say, “Now for the rest of the story.” If you lose a significant amount of weight by diet alone and don’t develop a consistent daily or almost daily physical activity pattern, you’ll regain all the weight within 5 years (most of the regain occurs in the first year). The latest study confirming this truth was published in the July American Journal of Physiology — Regulatory, Integrative, and Comparative Physiology.  

Why does exercise prevent weight regain? The study’s authors aren’t sure: “The mechanisms that underlie this beneficial effect of physical activity are not clearly understood, but there is evidence to suggest that physical activity counters the biological adaptations to weight loss that facilitate weight regain.” 

Whether exercise counters the adaptations to weight loss, or people who exercise are just more aware of what they’re eating and how much they weigh (or all the above) is almost beside the point. The point is you can lose weight by diet alone, but if you want to keep it off, you need to be physically active too.

For more truths about long-term weight control, visit www.NutriSum.com.