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With Health magazine's March issue boasting a Secret Ingredient theme, I got to thinking about the secret ingredient in my life, the thing that finally helped me reach a healthy weight and stop obsessing about my body. Nope, it wasn't a diet. It was strength training.

I'd had a weight problem for most of my life. It started early; you can actually look at my school pictures in second and third grades and see the difference—the rounder cheeks, the hint of a more ample chin, the pudgier arms. I spent a good portion of my teens and 20s on various diets and finally lost the weight I needed to in my early 30s, thanks to Weight Watchers. But it didn't last. Despite my good eating habits and commitment to walking, biking, and skating, my weight crept right back up, leveling off at around 150 pounds, which is a good 10 pounds or so above the top of the healthy range for my 5'4" frame.

I'm not sure what nudged me to finally take the plunge. Maybe it was turning 40 and knowing I faced an uphill battle on the weight front, thanks to a slowing metabolism. Maybe it was editing story after story explaining that the very best way to increase your metabolism is to build muscle, thereby allowing your body to naturally burn more calories every day. Whatever the catalyst, I finally, finally committed to what, as fitness editor, I'd been urging Health readers to do for years: I started strength training.

Up until that point, I'd dabbled in strength training sporadically. I'd do some half-hearted biceps curls, a few crunches. The couple of times I managed to get into some semblance of a routine, it was always the first thing to go if time ran short—something that happened all too frequently.

This time would be different. I made a vow to myself to do three strength training sessions a week in addition to the four cardio sessions I was already doing (and promised myself a reward if I did so). If something had to go due to a full schedule, it would be cardio. I would start small—10 or 15 minutes spent doing moves taken from workouts we'd run in Health, using 5-pound weights.

After a few weeks, I began to see a difference. There was the definition in my arms, the outline of muscles in my thighs, a new firmness in my waist. My pants felt looser. Spurred on by my changing body, I moved up to heavier dumbbells and found myself extending my strength workouts to 20 minutes, then 30. I began to enjoy the exercises, to appreciate how powerful I felt doing a push-up, a lunge, a chest press. I stopped "dieting" and began to concentrate on simply eating healthy foods, stopping when my body told me I'd had enough.

And the number on the scale? It got smaller. And smaller. I returned to my goal weight for the first time in years, then lost a few more pounds. My weight leveled off at 136, well within the healthy range for my height, and has stayed there (give or take a pound or two) for the past year and a half.

Now, I look strong. My clothes—a size smaller—fit better. When I pass a mirror, I'm pretty happy with what I see. And my brain is finally free to obsess about things other than weight (final season of Lost, anyone?).

A few months ago, my long-time hair stylist, Monier, was snipping away when he suddenly paused. His eyes met mine in the mirror. "You have cheekbones," he said. "Where did they come from?" I just smiled.