“Muscle weighs more than fat.” You’ve probably heard that phrase a million times before. And although it's false (a pound is a pound), you may have taken it to mean you should stay far, far away from the weight rack if you’re trying to drop pounds. We get where you’re coming from, but it’s not exactly that cut and dry.
At the most basic level, losing weight comes down to being at a caloric deficit, which means you take in fewer calories than you burn, says Nick Tuminello, a personal trainer and author of Strength Training for Fat Loss. You could do that by skipping your afternoon vending machine visit or by jogging for an hour after work or—yep—by lifting weights. While some studies show cardio is king when it comes to the best exercise for weight loss, there’s something to be said for strength training. Weight training, aerobic physical activities, and long-term waist circumference change in men. Mekary RA, Grøntved A, Despres JP. Obesity (Silver Spring, Md.), 2014, Dec.;23(2):1930-739X. Effects of aerobic vs. resistance training on visceral and liver fat stores, liver enzymes, and insulin resistance by HOMA in overweight adults from STRRIDE AT/RT. Slentz CA, Bateman LA, Willis LH. American journal of physiology. Endocrinology and metabolism, 2011, Aug.;301(5):1522-1555. With lifting, you’re still burning calories and fat all over—including your midsection. Harvard researchers found men who lifted weights for 20 minutes a day had less stomach fat than those who spent the 20 minutes doing cardio. Weight training, aerobic physical activities, and long-term waist circumference change in men. Mekary RA, Grøntved A, Despres JP. Obesity (Silver Spring, Md.), 2014, Dec.;23(2):1930-739X. As for women: This study found resistance training helps women reduce their risk of fat in the belly region.
But more importantly, there’s what happens after you’ve built muscle. Muscle burns more energy (read: calories) throughout the day than fat does, so having more muscle stokes your metabolism. A recent study found that nine months of resistance training increased study participants’ resting metabolic rate by an average of 5 percent. Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map. Aristizabal JC, Freidenreich DJ, Volk BM. European journal of clinical nutrition, 2014, Oct.;69(7):1476-5640.
Think of it this way: Even if you’ve committed to the couch for a Big Little Lies marathon, the more muscle you have, the more calories your body will burn while you’re just vegging out. “Basically, you have a bigger engine that needs more fuel,” Tuminello says. We’re not talking massive amounts of calories—adding one pound of muscle will burn an extra five to 10 calories per day, Tuminello says—but every little bit helps you inch closer to the calorie deficit needed to lose weight.
Even though exercise (no matter what type) is always a good idea, intensity is key. More challenging workouts will have a greater impact on your metabolism, which helps you burn more fat during and after exercise, Tuminello says.
The Best Way to Lift for Weight Loss
You can tweak your strength-training sessions to maximize the number of calories you burn. Tuminello suggests focusing on metabolic resistance training (MRT), which is basically high-intensity interval training (HIIT) with resistance added. He suggests performing circuits (completing 3 rounds of 3 to 4 total-body exercises back to back) and complexes (circuits using the same piece of equipment to minimize down time). For example, you might grab a pair of dumbbells and perform bent-over rows and then go straight into Romanian deadlifts and then dumbbell squats without resting in-between.
The idea is to get your heart rate elevated and keep it there, but you also want to make sure the dumbbells you pick up are challenging without compromising your form. Lifting heavier weights for fewer reps burns significantly more calories for two hours after a workout than more reps with lighter weights. Effects of resistance exercise bouts of different intensities but equal work on EPOC. Thornton MK, Potteiger JA. Medicine and science in sports and exercise, 2002, Apr.;34(4):0195-9131.
Don't Be a Slave to the Scale
Here’s the catch: Building muscle might have you looking and feeling fitter and more toned, but those changes may not be so obvious when you hop on the scale. That’s because muscle is denser than fat, and one pound of fat takes up about four times as much space as muscle. “If the mirror is looking good, but the scale isn’t necessarily changing, what you’re really doing is changing the composition of your body,” Tuminello says. And that's a great thing! You’re losing fat and gaining muscle, which resistance training does more effectively than endurance training, according to recent research. This post from a fitness Instagrammer sums it up: She’s clearly her fittest at 140 pounds, even though that’s 18 pounds heavier than her lowest weight.
Don't Forget About Diet
Yes, exercise, including resistance training, is essential for general health, weight loss, and weight maintenance, but don’t forget that diet is No. 1 when it comes to weight loss. Research shows that a combination of diet and exercise is the way to go for sustaining it. “Pay attention to your diet to better reveal your shape and use strength training to improve that shape,” Tuminello says. Besides, the benefits of a healthy diet and daily exercise go way beyond just weight loss. So rather than getting hung up on numbers—especially if it’s causing you to obsess and step on the scale every single day—ditch the weigh-ins and focus on how your clothes fit and how you feel. Your mental health will thank you.