In what has been described as a “myth-busting” study, Sydney researchers have shown that strength training is just as effective as aerobics or cardio workouts at reducing body fat.
“A lot of people think that if you want to lose weight, you need to go out and run,” said senior author of the study Dr Mandy Hagstrom, exercise physiologist and senior lecturer at UNSW Medicine & Health.
“But our findings show that even when strength training is done on its own, it still causes a favourable loss of body fat without having to consciously diet or go running.”
The study found that you can lose around 1.4 per cent of your entire body fat through strength training alone, “which is similar to how much we might lose through cardio or aerobics”.
Why is it only now that we know this?
Previous studies tended to have small sample sizes – the number of participants – “which made it difficult to find statistically significant results, especially as many bodies can respond differently to exercise programs”.
The other problem is that many studies used inaccurate measuring tools such as bioelectrical impedance or scales, which failed to differentiate fat mass (the weight of all your fat) from lean mass (the weight of everything else).
The researchers addressed these issues by pooling the findings from 58 research papers that used highly accurate forms of body fat measurement, notably body scans such as MRI or CT, to investigate the outcomes from strength training programs.
The studies included 3000 participants, none of whom had any previous weight training experience.
“It can be really difficult to discern whether there’s an effect or not based on one study alone,” Dr Hagstrom said.
“But when we add all of these studies together, we effectively create one large study, and can get a much clearer idea of what’s going on.”
The strength training programs differed between the studies, but the participants worked out for roughly 45 to 60 minutes each session for an average of 2.7 times per week.
The programs lasted for about five months.
The team found that, on average, the participants lost 1.4 per cent of their total body fat after their training programs, which equated to roughly half a kilo in fat mass for most participants.
The bathroom scales fool our perceptions
When we’re trying to lose fat, we tend to rely on the bathroom scales – and gauge our progress by our body weight.
This fails to differentiate fat mass from everything else, such as water, bones, organs and muscles.
“More often than not, we don’t gain any muscle mass when we do aerobic training,” Dr Hagstrom said.
“We improve our cardiorespiratory fitness, gain other health and functional benefits, and can lose body fat.”
But when we strength train, we gain muscle mass and lose body fat, “so the number on the scales won’t look as low as it would after aerobics training, especially as muscle weighs more than fat”.