So wandering through the gym I noticed a woman I’ll call “X” on the treadmill. X was jogging slowly on the treadmill for the duration of my clients 40 minute workout.

Then I hopped onto the elliptical for a quick interval set, and X was still jogging her tush off (or so she thought). Finally she stepped off, wiped the sweat off her forehead, and walked over to the weights: She did two sets of biceps curls, three sets of leg curls and she was out the door.

Sound like you? Here’s why too much time on the treadmill will actually work against you and what you should do to fix it.

People devote too much time to cardiovascular workouts and too little time to the programs that will actually get you the results that you want: weights. When it comes to heart and lung health, yes cardio IS top dog. But for fat burning, muscle toning and metabolism boosting, weight training is superb.

In fact, cardio can actually cause you to GAIN body fat!

Take X. She’s “skinny” fat: thin framed but still covered with a layer of body fat. While cardio may help the scale go down initially, it does the same to your metabolism.

When you run at the same pace for a long time, your body needs energy to keep going. It comes from not only those saddlebags - but also that lean sexy muscle we all love so much. And since it takes calories and energy to keep muscle, the more you lose the slower your metabolism.

Weight training creates more lean muscle and raises your metabolism, helping you stay toned, but also burning more body fat.

Women like X need total body workouts. The bigger the moves, the more calories you blast. Those little biceps curls did a whole lot of nothing for X’s arms.

Here is what YOU could be doing in the gym when you are not at boot camp in order to boost that metabolism and to get that toned beach ready body.

Three sets of 12 reps of compound exercises where you are working your upper and lower body at the same time: squat-to-press, walking lunges with biceps curls, or push-up rows. And YES it is possible to lift weights and not “bulk” up. Just lift lighter weights and increase the repetitions. This alone should take about 30 minutes.

Finish off with a few sprint intervals on the treadmill, bike or elliptical. Intervals are high intensity – in other words, a mix of running at various speeds from slow to sprint – and this doesn’t need to last longer than 20 minutes in total.

So next time you are hitting the gym and thinking that you want to burn all those calories – go for the weight rack instead of the treadmill.