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Science Long-Term Study Suggests You Really Can Prevent Weight Gain Through Strength Training

Recent research indicates that resistance training, either on its own or combined with aerobic exercise, can be a boon for body composition goals.

woman strength training on Tonal to illustrate the benefits of strength training.
  • Previously, weight-loss advice has implied that you can only see fat loss or prevent weight gain through diet, but new research challenges that assumption.
  • Although the biggest benefits were seen with the blend of aerobic exercise and resistance training, participants also reported benefits with resistance training alone.
  • Strength training seems to be especially good for fat burning, thanks to the way you continue to draw down fat stores during muscle recovery.

A well-worn bit of advice is that you gain muscle in the gym, but lose fat in the kitchen—implying that although exercise has a breadth of benefits (which is so very true), it’s not as potent for weight gain prevention or body composition changes as people might think. But a new study in the journal PLOS Medicine is challenging that assumption.

Researchers looked at nearly 12,000 healthy adults between the ages of 18 to 89 who had a body mass index under 30 (which is considered obese) at the study’s starting point. Participants were followed for an average of six years as they reported how often they performed resistance training and aerobic exercise and shared their body mass index, waist circumference, and body fat percentage along the way. 

Those who regularly did both types of exercise tended to be the most successful at keeping weight controlled, but the resistance-training-only participants had a nearly 30-percent reduced risk of obesity. That group also tended to have an edge when it came to maintaining body fat percentage over the years.

That’s not surprising, considering the way resistance training works, says trainer Rocky Snyder, CSCS, author of Return to Center: Strength Training to Realign the Body, Recover from Pain, and Achieve Optimal Performance. During a workout, muscles are taxed to the point of fatigue, and the body’s response is to repair the tissue and build more.

“This process requires a tremendous amount of energy, mostly from fat stores,” he says. “Aerobic energy requires the highest amount of fat calories during the activity, yet the repair process is not as demanding and requires less energy than recovering from resistance training.” The result is more fat burned, for longer, after a training session as muscles recover. 

Another potential benefit of strength training is that if you’re new to it, you tend to see progress fairly quickly, according to Erica Marcano, CSCS, a trainer and rehabilitation specialist. That means if your goal isn’t preventing weight gain, but losing weight instead, resistance training could also be a compelling strategy, she adds.

“Many people are happily surprised to see improvement in strength much faster than you’ll see them with cardio performance,” says Marcano. “That’s powerful from a mental and emotional standpoint as well as a physical one, because it can be the push you need to keep going when your weight-loss journey seems tough. You’ll be able to feel the changes even if you can’t quite see them yet.”

Also, if you usually do only aerobic exercise, adding resistance training can be a powerful way to avoid overuse injuries, she says. That’s because it can strengthen muscles you may not be using during cardio activities and provide greater range of motion, stability, and muscle coordination.

“Consider resistance training your best strategy for both weight management and injury prevention,” she says.