In a recent episode of our new WH podcast Just As Well, co-host Gemma Atkinson asked her personal trainer Elliott Upton about the worst training misinformation he’s heard. His answer? ‘That weight training makes women bigger. It drives me mad. It’s still alive even after 30, 40 years. It drives me crazy because it just isn’t true.’

And now, there is a huge new study to back him up. In a systematic review (when researchers gather and assess existing studies on something) and meta-analysis (when the data from those studies is analysed), published in the Journal of the International Society of Sports Nutrition, researchers compared the effects of resistance training, aerobic training and concurrent training (combining the two) on body mass and body fat loss in metabolically healthy individuals.

Related StoryWhat did the study find?

Analysing a total of 31 studies, researchers found that while aerobic training and concurrent training led to greater absolute fat loss on average, strength training performed just as well in lowering body fat percentage (the proportion of fat relative to total body weight).

Body fat percentage is generally considered a more accurate indicator of health than BMI (body mass index) because it reflects the actual amount of fat in the body and distinguishes between fat and muscle mass, which BMI does not.

Visually, your body fat percentage, which is not just about weight, but body composition, contributes to how lean you are. So, typically, if you’ve got a low proportion of body fat relative to lean mass (eg, muscle), you’ll be leaner.

In studies where training volume and intensity were the same across different exercise types, the researchers actually also found that fat loss outcomes were similar.

So, why can muscle growth help support fat loss? Well, firstly, to grow muscle, you’re using more energy to build that muscle. But, with more muscle growth, you’re also increasing your resting metabolic rate, which means you burn more calories throughout the day at rest. In other words, because muscle tissue is more metabolically active (requires more energy to maintain) than fat tissue, your body burns more calories even when it’s not doing anything.

Equally, then, if you lose muscle, your body burns fewer calories overall, and it’s harder to lose fat.

When performing cardio for fat loss (as part of an approved and sustainable weight loss plan), it works mainly through causing a greater deficit. That’s why approved, sustainable fat loss plans focus on diet as much as exercise, accounting for how they work together.

Similarly, it’s why elite athletes have to focus so much on fuelling to ensure they aren’t in a deficit to avoid unwanted fat and muscle loss.

Indeed, this study also found resistance training to be more effective at preserving lean muscle mass than aerobic training, reinforcing the importance of including strength training in any well-rounded exercise plan. Runners, we’re looking at you.

What does this mean for us?

Returning to Elliott’s comment on the pod, weight training is not about getting massive bodybuilding biceps (unless you want to), it’s about supporting good overall health, fitness and longevity.

In the same way the study highlights this, it also challenges the long-held myth that doing loads of cardio will promote quick fat loss and is the gold standard for getting lean.

That’s certainly not to tell you to cut back on cardio (which is vital for heart health), but rather, it shows how fitness is a bigger picture – and one that is supported by different types of training. Like with diet and nutrition, diversity is key.

Related StoryThe bottom line

While this was an extensive and rigorous study, as is the case with many meta-analyses, some of the studies examined varied in design, methods, and populations studied, potentially affecting some results.

However, while more research is needed to strengthen (no pun intended) the researchers’ evidence base, a strong case for diversifying your training remains.

Yes, cardio is great, but adding strength training to your routine can help you build a more holistic and long-term approach to health, fitness and longevity.

Related StoriesHeadshot of Hannah Bradfield

Hannah Bradfield is a Senior Nutrition Writer across Women’s Health UK and Men’s Health UK. An NCTJ-accredited journalist, Hannah graduated from Loughborough University with a BA in English and Sport Science and an MA in Media and Cultural Analysis. 

She has been covering sports, health and fitness for the last five years and has created content for outlets including BBC Sport, BBC Sounds, Runner’s World and Stylist. She especially enjoys interviewing those working within the community to improve access to sport, exercise and wellness. Hannah is a 2024 John Schofield Trust Fellow and was also named a 2022 Rising Star in Journalism by The Printing Charity. 

A keen runner, Hannah was firmly a sprinter growing up (also dabbling in long jump) but has since transitioned to longer-distance running. While 10K is her favoured race distance, she loves running or volunteering at parkrun every Saturday, followed, of course, by pastries. She’s always looking for fun new runs and races to do and brunch spots to try.