Forget Traditional Cardio

Ever wondered why elliptical machines (and stair climbers and treadmills . . . ) are often full of people who are overweight? Apparently, the most monotonous exercises are also the ones least likely to build muscle—and might even do the opposite. Researchers at West Virginia University wanted to see how two different routines, plus a very-low-calorie diet, would affect weight loss. One group of participants engaged in resistance training on weight machines that progressed from one to four sets of up to 12 exercises three times per week. The second group performed 50 to 60 minutes of walking, stair climbing, or biking four times per week. At the end of the 12-week study, the aerobic group had lost 19.4 percent of total body weight, while the strength group had lost 14.7 percent. But when body-composition measurements were taken, researchers discovered that one fourth of the weight lost by the aerobic group was muscle. The resistance group's muscle mass remained static even though their diet was severely restricted. "Long-duration, low-intensity cardio can break down muscle tissue to be used as fuel," Pizzi says. "If your goal is fat loss and muscle growth, it's best to stick with short-duration, high-intensity cardio and strength training."

Outsmart Your Appetite

Many people want to raid the refrigerator after a workout. Science now suggests that these cravings are linked closely with the type of exercise performed. It all has to do with the hunger hormone ghrelin, which lines the stomach walls and signals the brain to eat. According to a study from the Else-Kröner-Fresenius Center of Nutritional Medicine at the Technical University of Munich, people who cycled at 50 watts (light effort) for 30, 60, and 120 minutes experienced a serious spike in ghrelin release that triggered the desire to eat. However, ghrelin secretion remained unchanged when exercisers kicked up the intensity to 100 watts (moderate effort) during a short, 30-minute workout. The authors state that "low- rather than high-intensity exercise stimulates ghrelin levels independent of exercise duration." Another study, from Leeds University in Britain, backs up this counterintuitive wisdom by showing that intense exercise actually suppresses appetite. Other researchers suggest this is due to the temporary blunting of ghrelin release and increased secretion of peptide YY—the hormone responsible for appetite suppression. Without those nagging hunger pangs, the ability to make sensible nutrition choices should be much easier.

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