Exercise is an important tool in your weight loss arsenal, although what and how much you eat is, ultimately, more important for shedding those extra pounds of body fat. Conventional wisdom says when you want to lose body fat you should do more calorie-burning exercise, namely, cardio. A cardiovascular workout does burn calories and is good for heart health, but how does it compare to strength training for weight loss?
Losing Weight: Is Cardio or Weights More Effective?
If you measure calories burned, cardio sessions have an advantage over lifting weights, namely, it’s a calorie burner. For example, if you weigh 150 pounds, you’ll burn around 225 calories if you jog for 30 minutes. If you pick up the speed and break into a run, you burn around 350 calories over that 30 minutes. How about 30 minutes of strength training? You’ll only expend between 150 and 230 calories during a strength-training session. The precise number will depend on how heavy you’re lifting and how long you rest between sets.
If you’re considering calorie burn only, a cardio session would seem to be the best choice. But, what about high-intensity interval training, a more intense form of cardio? High-intensity interval training, or HIIT, burns calories while you’re doing it. Plus, you’ll burn some extra calories afterward due to the after-burn. In fact, research shows that high-intensity interval training blasts around 25% more total calories than a moderate-intensity cardio workout performed for the same length of time.
Still, both forms of cardio burn more calories than strength training. So, isn’t cardio the form of exercise you should focus on if you’re trying to lose body fat? Well, it doesn’t have to be “either-or.” The best workouts are balanced and include some of each form of exercise. Yet, there are some compelling reasons that strength training should figure prominently in your weight loss efforts.
Strength Training and Weight Loss
Although strength training doesn’t burn as many calories minute-by-minute as cardiovascular exercise, it builds muscle, and we know that muscle is more metabolically active, meaning that it burns more calories. The more muscle you have on your body, the more of a calorie deficit you’ll incur over the course of a day. In contrast, if you do long periods of cardio without weight training, you’ll likely lose muscle and burn fewer calories. In other words, your resting metabolic rate will slow.
The impact of having additional muscle is subtle but it counts. It’s not uncommon to hear overblown claims about how many extra calories a pound of muscle burns. For example, you may have read that each additional pound of muscle you carry on your frame burns 50 added calories over the course of a day. The reality is, depending on the source, that value is between 6 to 10 additional calories daily. The previous claims were a bit overstated, as confirmed by more recent research. But, we’ll take even a few extra calories, right?
So, the extra calories you burn when you have more muscle isn’t enormous. It’s also not clear whether strength training suppresses appetite and leads to weight loss due to reduced food intake. One study found that an intense, cardio workout on a treadmill suppressed the appetite hormones, ghrelin and peptide YY. Suppression of these hormones would lead to a reduction in appetite. In contrast, 90 minutes of weight training dialed back only one of the two appetite hormones, ghrelin and didn’t stymie it as much as a vigorous cardio workout. Based on this, vigorous cardiovascular exercise is more effective for suppressing appetite, but strength training may curb appetite to some degree as well.
Why You Still Need Strength Training
We already mentioned the small metabolic benefits you get when you have more muscle. It’s modest but can have an impact over a long period of time. However, it’s ultimately body composition that matters most, not a number on a scale. When you lose weight, you shed both body fat and muscle. Since weight training is anabolic and moderate-intensity cardio is catabolic, you expect to lose more muscle when you do cardiovascular exercise than when you strength train.
How do we know this? In a study carried out by researchers at Penn State, a group of overweight subjects lost 21 pounds through diet and exercise. They lost roughly the same amount of weight whether they did cardio or strength trained. The difference is, on average, the strength trainers lost almost exclusively body fat while the cardio group lost 6 pounds of muscle.
Ultimately, it’s not in your best interest from a health, fitness, or aesthetic perspective to lose muscle. We lose muscle as we age anyway and need to do whatever we can to preserve it so we can stay functional. Who wants to be frail? Strength training helps you preserve it and build more. Plus, strength training builds confidence and self-esteem.
Keep It Balanced
The take-home message is you need both cardio and strength training. If you’re trying to lose weight, you want to lose body fat while preserving as much muscle as possible. The two ways to do that are to strength train and consume enough protein. If you’re physically active, aim for around 1.6 grams of protein per kilogram of body weight. You need more protein to help repair the damage your muscles sustain when you do cardio or lift weights and to keep your body out of a catabolic state. Protein also helps with appetite control. You don’t have to get it all from meat and dairy, choose more plant-based foods and you’ll also benefit from the fiber plants offer.
The Bottom Line
Don’t be cardio obsessed if you’re trying to lose body fat. Do some cardio but balance it out with strength training. Training your muscles against resistance is something we all need to do, especially as we age. The biggest benefit of strength training is it will help you maintain a healthy body composition when you lose weight. So, take advantage of it!
J Strength Cond Res. 2015 Mar;29(3):779-85.
Am J Hum Biol. 2011;23(3):333-8.
Science Daily. “Exercise Suppresses Appetite By Affecting Appetite Hormones”
Women’s Health. “What’s More Important for Weight Loss: Cardio or Strength Training?”
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