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Want to Lower Your Body Fat Percentage? Lift Weights

On average, bi-weekly strength training sessions reduce body fat by 1.4 percent.

Key points

  • Cardio workouts burn fewer calories than once thought; aerobic exercise isn't necessarily the best way to burn fat or lose weight.
  • Resistance training and strength-building exercises boost metabolism, burn fat, and optimize body composition.
  • A recent review and meta-analysis found that strength training alone (without cardio) can lower body fat by 1.4 percent.
jertam2020/Shutterstock
Source: jertam2020/Shutterstock

A new systematic review and meta-analysis by researchers from the University of New South Wales in Australia report that full-body strength training workouts are an effective way to reduce body fat percentages, lower overall body fat mass, and optimize body composition. These findings (Wewege et al., 2021) were published on September 18 in the peer-reviewed journal Sports Medicine.

"A lot of people think that if you want to lose weight, you need to go out and run, but our findings show that even when strength training is done on its own, it still causes a favorable loss of body fat without having to consciously diet or go running," senior author Mandy Hagstrom of UNSW said in a news release.

She also notes that "the best approach for people who are aiming to lose fat is still to stick to eating nutritiously and having an exercise routine that includes both aerobic-cardio and strength training." Hagstrom also emphasizes the importance of creating a weekly workout routine that includes activities you enjoy. Her take-home advice: "Do what exercise you want to do and what you're most likely to stick to."

Strength Training Can Lower Body Fat Percentages

This review of 58 different research papers found that, on average, pumping iron for roughly 45-60 minutes two-three times per week (2.7 was the average) resulted in a 1.4 percent reduction in body fat over the course of about five months. Taken together, the studies included in this meta-analysis involved 3,000 study participants who did not have previous experience lifting weights or doing resistance training exercises at the gym.

These findings dovetail with another recent metabolism study (Careau et al., 2021) that found that trying to burn calories by increasing levels of cardiorespiratory activity and aerobic exercise may result in diminishing returns on energy expenditure due to compensatory responses that lead to a 28 percent drop in metabolic rate after a cardio workout.

Basically, this study found that for every 100 calories you might think you're burning on a treadmill, at the end of the day, you've only burned 72 kcal. As Vincent Careau of the University of Ottawa and co-authors explain:

"The ever-growing and diversifying range of fat loss plans and fads reflects the reality, well known to researchers, that prescribed exercise programs for weight reduction rarely result in substantive or long-term changes in body mass. The few national guidelines that have been published converge on the recommendation of a 500–600 kcal/day deficit through exercising and dieting to instigate fat loss. These guidelines are general for the population and do not factor in the variation in energy compensation exhibited by people with different levels of fat mass, as demonstrated in the current study."

Nancy Mure/Pixabay
Source: Nancy Mure/Pixabay

Bathroom Scales Can Be Deceiving and Dispiriting

Full-body resistance training builds lean muscle mass, which weighs more than fat. Lifting weights also increases bone density, which makes your internal skeleton heavier.

Therefore, if you stick with a regular strength training regimen, the numbers you see on a bathroom scale may not go down significantly because these digits don't reflect shifts in body composition or changes in your body fat percentage.

"More often than not, we don't gain any muscle mass when we do aerobic training," Hagstrom notes. "For example, many people focus on the number they see on the scale—that is, their total body weight. But this figure doesn't differentiate fat mass from everything else that makes up the body, like water, bones, and muscles."

"Resistance training does so many fantastic things to the body that other forms of exercise don't, like improving bone mineral density, lean mass, and muscle quality. Now, we know it also gives you a benefit we previously thought only came from aerobics," Hagstrom concludes. "If you're strength training and want to change how your body looks, then you don't want to focus on the number on the scale too much because it won't show you all your results. Instead, think about your whole body composition, like how your clothes fit and how your body will start to feel and move differently."

References

Michael A. Wewege, Imtiaz Desai, Cameron Honey, Brandon Coorie, Matthew D. Jones, Briana K. Clifford, Hayley B. Leake & Amanda D. Hagstrom. "The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat: A Systematic Review and Meta-Analysis." Sports Medicine (First published: September 18, 2021) DOI: 10.1007/s40279-021-01562-2

Vincent Careau et al. "Energy Compensation and Adiposity in Humans." Current Biology (First available online: August 27, 2021) DOI: 10.1016/j.cub.2021.08.016

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