How Many Reps Should I Do While Strength Training to Lose Weight?

Although strength training is great for building a strong and healthy body, there's no secret number of reps you should do to lose weight. You'll get the best results by incorporating your strength-training workouts into a multifaceted weight loss program that includes cardio and diet.

Even though there's no magic number of reps and sets for fat loss, there is some solid data about how many reps and sets you should do to build strength and endurance in your muscles. The Department of Health and Human Services (HHS) advises that for most people, one to three sets of eight to 12 repetitions is enough.

There is a little more to consider: You should be doing those one to three sets for all your major muscle groups (chest, back, arms, legs and core), and for optimal results you should work each of those major muscle groups twice a week, giving each muscle group at least one full rest day (or to put it another way, 48 full hours between workouts) before you work it again — more if you're still sore from the last workout.

Why can't you create a weight loss program with nothing but strength training? Two reasons: First, because your muscles need time to rest and recover before you strength-train them again, it's difficult to create enough exercise volume to really spur your weight loss through strength training alone.

Second, those HHS guidelines also recommend doing at least 150 minutes of moderate-intensity aerobic activity per week, or 75 minutes of vigorous-intensity aerobic activity. That's to maintain your health — but all that exercise will also help burn calories and speed your weight loss journey along the path to success.

The HHS also says you can get even more health benefits by doing more aerobic activity during the week. And because your muscles don't need the same type of recovery time between cardio workouts as they do between strength-training workouts, you can pile up the volume of your aerobic workouts in a way you can't manage with strength training.

There are a couple of caveats to keep in mind, though. Doing too much, too soon can leave you overly sore, discouraged or even injured — all of which can set you back on your weight loss journey instead of moving forward. The key is to start slowly and work your way up in workout frequency, duration and intensity as your body adapts to the new challenges you're giving it.

Finally, make sure you aren't overdoing it. Even the most determined exerciser needs to take a break and rest sometimes; your body needs the time to rebuild and recharge. A good general rule is to take at least one rest day per week (sometimes more if you're starting out), and be alert for signs of overtraining that can include sleep and mood disturbances, nagging fatigue and injuries, loss of appetite and things just generally seeming harder than they should.

Read more: A Full-Body Weightlifting Workout for Weight Loss

There are two ways that strength training can benefit your weight loss journey. The first is by burning calories. According to estimates from Harvard Health Publishing, a "general" half-hour weightlifting workout can burn from 90 to 133 calories, depending on your body weight. Crank that up to a vigorous intensity and you'll burn about twice as much — 180 to 266 calories in half an hour.

Aside from exercise intensity, one of the biggest factors that affects your calorie burn is your body weight. In general, the more you weigh, the more calories you'll burn. With that in mind, it's helpful to note that the highest body weight included in those Harvard estimates is 185 pounds — so if you weigh more than that, you might burn even more calories as you strength train.

Why do those calorie-burn estimates matter? It's because even though there are many complex — and not entirely understood — factors at play, the easiest way to estimate your weight loss is by equating a calorie deficit of 3,500 calories to 1 pound of fat loss. In other words, for every 3,500 calories you burn beyond what you consume, you lose about a pound of body fat.

Even though lifting weights doesn't typically burn as many calories as intense cardiovascular workouts like running, every little bit counts when you're working up to a calorie deficit, and doing two or three vigorous weight-training workouts per week can make a significant contribution toward your goal.

And if you start doing weight-training splits — alternating which muscle groups you work on which days, so you can spend more time in the weight room — you can squeeze even more weight training workouts into the week.

But wait — there's a second way that weight training benefits your weight loss efforts. As you build muscle, you also boost your resting metabolism, which means you burn more calories — and potentially increase your calorie deficit — simply by existing.

Expert estimates of exactly how much the added muscle affects your metabolism vary; one of the most authoritative comes from exercise physiologists at the University of New Mexico, who explain that muscle tissue is about four times more metabolically active than fat tissue.

Read more: How Fast Can You Lose Weight by Weightlifting?

There's no question that strength training can help your weight loss efforts along. But as an analysis published in a July 2012 issue of Current Sports Medicine Reports explains, the benefits of strength training extend far beyond fat loss.

Just a few of the other benefits you stand to gain include improvements in your resting blood pressure, cholesterol and triglycerides; greater bone density; less pain from chronic conditions such as arthritis and fibromyalgia; sharper cognitive abilities; reduced visceral fat and inflammation markers; and improved insulin sensitivity.

Add to that the very tangible benefit of having the strength and endurance to make everyday tasks feel easier — whether that means running through an obstacle course, playing with your grandkids, carrying a bag of books or climbing a flight of stairs — and it's hard to find any reasons not to make strength training a regular part of your weight loss program.

When you think of lifting weights for fat loss, you might imagine hefting dumbbells or barbells in your gym's weight room — and as long as you use proper form, that's a great way to build strength and work out. You can also strength-train using your own body weight for resistance, with exercises such as push-ups, pull-ups, squats and lunges.

But these "conventional" ways of strength training are just the start of your options. If you enjoy working out in a group environment, you can participate in strength-intensive boot camp, circuit training or body sculpting classes. You can even use some yoga styles as strength training.

For a real calorie-burning boost, try kettlebells. According to a small study commissioned by the American Council on Exercise and published in the January/February 2010 issue of its newsletter, 10 subjects who participated in an intense kettlebell workout burned at least 20.2 calories per minute — the equivalent of running a six-minute mile.