Want to lose fat? Then you need to get your butt on the treadmill. At least, that’s what most people assume—and why most weight-loss warriors aren’t getting the results they want from their workouts.
Consider this: When obese participants followed a diet and either a strength-training or cardio program for eight weeks, the two groups lost a similar amount of weight—but the strength trainers lost less fat-free mass (a.k.a. muscle) than the cardio-doers, according to research published in the American Journal of Clinical Nutrition. Meanwhile, when Harvard researchers followed 10,500 men over the course of 12 years, they found that strength training was better than cardio at warding off belly fat. (Cue the collective sigh of relief from cardio haters everywhere.)
We’re not saying you should cut cardio out of your life, but if strength training isn’t already a major part of your weight-loss plan—well, it needs to be.
Cardio vs. Strength Training
“People think to lose fat mass they need aerobic exercise and to forget about resistance training,” says Rania Mekary, Ph.D., a researcher with the Harvard T.H. Chan School of Public Health and lead author of the 12-year study.
On the surface, that assumption makes sense. After all, when you perform moderate-intensity cardio like running, biking, or swimming, the vast majority of your calories burned come from fat, she explains. (Hence why, when you’re cruising along at an easy pace on a cardio machine, it rewards you by telling you that you’re in the “fat-burning” zone.) Meanwhile, during resistance training, the bulk of your calories burned come from glycogen, stored carbs housed in your muscles and liver.
The first option seems far more advantageous for those trying to shed fat. That is, until you consider the fact that your muscle mass —which, when left to its own devices, decreases after age 30—is a key driver of your metabolism. And rather than building muscle, cardiovascular exercise can actually burn up some of it.
“Fat is the major energy source during aerobic training, but many people don’t realize that protein also contributes. And that protein comes from muscle,” Mekary says. “So if you are running, running, running, it can make you lose even more muscle than you would otherwise.”
The result: a slower and slower metabolism. That partially explains why, after many people lose weight, they tend to put it right back on. In fact, research from Columbia University shows that losing just 10 percent of your body weight significantly lowers your basal metabolic rate, the number of calories you burn just to stay alive.
Related: 5 Myths About Your Metabolism—Busted
Meanwhile, strength training increases your metabolic rate in a big way. Over the short term, it causes just enough microscopic damage to your muscles that they have to work hard to recover—a process that requires a lot of energy (a.k.a. calories). Known as ‘excess post-exercise oxygen consumption’(or EPOC), your metabolism can stay elevated for up to 72 hours after your strength training session, according to research published in the European Journal of Applied Physiology. You just don’t get that lasting boost with cardio, especially when it’s steady-state, Mekary says. Over the long term, by building the amount of muscle mass you have with strength training, you can increase your metabolism even further.
What’s more, strength training helps to dull the spikes in hunger-stimulating hormones that often come with weight loss, explains Spencer Nadolsky, D.O., a board-certified family and bariatric physician, diplomate of the American Board of Obesity Medicine, and author of The Fat Loss Prescription. That makes losing weight—and keeping it off—that much easier.
Better Together: How to Combine Cardio and Strength for Optimal Fat Loss
Still, for the best fat-loss results, you don’t want to ignore cardio altogether. “By combining anaerobic and aerobic exercise, you maintain muscle, burn more calories, and are able to burn both fat and glycogen,” says Mekary, noting that, according to her research, combination training is even better for fat loss compared to strength training alone. “It’s a win-win situation.”
While the best way to divide your workout routine depends in part on what you actually like to do (what does your schedule matter if you won’t stick to it?), Mekary recommends devoting about 70 percent of your workout time to strength training and 30 percent to cardio. If you hit the gym five days per week, that works out to roughly three strength days and two (slightly shorter) cardio days per week.
“Ideally, you would schedule strength and cardio workouts on different days,” says Nadolsky, noting that performing cardio right before a strength workout can slightly inhibit muscle-building results. (Another study published in the European Journal of Applied Physiology found that men made comparable strength gains after 24 weeks regardless of whether they hit cardio or strength training first. But the guys who did cardio first initially had lower levels of testosterone—a marker of recovery and muscle-building potential—than those who hit the weights first.) It’s not a huge difference, but if you’re focusing on building muscle and can schedule your workouts like that, by all means, go for it.
Making the most of both your strength training and cardio sessions just takes some simple strategizing. During your strength workouts, focus on hitting as many muscle groups as possible by performing compound moves such as squats, deadlifts, thrusters, pull-ups, and bench presses. Spend the bulk of your cardio time on high-intensity intervals (HIIT) such as sprints on the treadmill, bike, or rowing machine. However, some moderate-intensity, steady-state can be good from time to time, too—especially when you feel like you need a little extra recovery from your lifting sessions and don’t want to go too hard with HIIT.