It is common knowledge that if you want to build muscle, you should strength train, and if you want to reduce fat, you should do cardio- right? Not necessarily, according to a new study conducted by academics at The University of New South Wales (UNSW).
The researchers reported their findings in the journal Sports Medicine.
Indeed, the study—a comprehensive review and meta-analysis of current evidence—demonstrates that we may lose approximately 1.4 percent of our total body fat by strength training alone, which is comparable to the amount lost through cardio or aerobics.
“Many people believe that in order to reduce weight, they must go out and run,” said Dr Mandy Hagstrom, an exercise physiologist and senior lecturer at UNSW Medicine and Health.
“However, our data indicate that even when strength training is performed alone, it results in a beneficial loss of body fat without the need for intentional dieting or jogging.”
Until recently, the relationship between strength training and fat loss was unknown. Numerous studies have examined this link in the past, but their sample sizes have tended to be small—a byproduct of the fact that few people volunteer to exercise for months on end. Smaller sample sizes make it more difficult to obtain statistically meaningful findings, all the more so because diverse bodies respond differently to exercise programmes.
“It can be really difficult to determine whether or not there is an effect based on a single study,” Dr Hagstrom explained. “However, when we combine all of these research, we basically form one enormous study and gain a much clearer picture of what is happening.”
Dr Hagstrom and her colleagues analysed 58 research papers that used very accurate methods of body fat measurement (such as body scans, which can distinguish between fat and lean mass) to assess the effects of strength training regimens. The studies enrolled a total of 3000 people, none of whom had any prior experience with weight training.
While the strength training routines varied between research, participants exercised for an average of 45-60 minutes per session, 2.7 times per week. The programmes ran for around five months.
The researchers discovered that on average, participants lost 1.4% of their total body fat following their training programmes, which equaled to almost half a kilogramme of fat mass for the majority of participants.
While the findings are positive for those who enjoy lifting weights, Dr Hagstrom notes that the optimum method for persons looking to reduce fat remains to eat healthfully and maintain an activity plan that incorporates both aerobic/cardio and strength training.
However, if aerobics and cardio are not your thing, the good news is that you do not have to force yourself.
“If you want to exercise in order to alter your body composition, you have options,” Dr Hagstrom explained. “Do the activity that you enjoy and are most likely to stick with.”
A large part of the reason many people believe strength training falls short of cardio in terms of fat loss is due to inaccuracies in fat measurement.
For instance, many people get fixated on the number displayed on the scale—their entire body weight. However, this number does not distinguish fat mass from the other components of the body, such as water, bones, and muscles.
“Most of the time, aerobic exercise does not result in muscle mass gain,” Dr Hagstrom explained. “We increase our cardiorespiratory fitness, acquire additional health and functional benefits, and have the potential to shed body fat. However, because strength training increases muscle mass while decreasing body fat, the figure on the scales will not appear as low as it would after aerobics exercise, particularly because muscle weighs more than fat.”
The research team concentrated on the change in total body fat percentage—that is, the percentage of your body that is composed of fat mass—following strength training programmes. This measurement revealed that, despite the disparate numbers on the scales, fat loss appeared to be comparable to aerobics and cardio training.
“Many fitness recommendations are based on research that use erroneous measurement techniques, such as bioelectrical impedance or scales,” Dr Hagstrom explained.
Hagstrom continued, “However, the most precise and trustworthy method of determining body fat percentage is via DEXA, MRI, or CT scans. They have the ability to compartmentalise the body and distinguish fat mass from lean tissue.”
While this study did not demonstrate whether exercise time, frequency, intensity, or set volume had an effect on fat loss %, the researchers aim to investigate next whether how we strength train has an effect on how much fat we lose.
The team did a sub-analysis as part of their study to determine how different methods of fat measurement can affect a study’s conclusions.
Interestingly, research demonstrated that when more precise measurements such as body scans were employed, the overall changes in body fat were smaller.
“Using correct fat measures is critical because they provide a more realistic picture of the physical alterations that can occur,” said the study’s principal author, Mr Michael Wewege, a PhD student at UNSW and NeuRA. “Future exercise studies can benefit from these more precise body measures.”
Reframing how we measure success is relevant not only for sports scholars, but also for regular people.
“Resistance training benefits the body in ways that other forms of exercise do not, such as increasing bone mineral density, lean muscle mass, and muscle quality. Now we know it also provides a benefit previously thought to be exclusive to aerobics “Dr Hagstrom stated.
If you’re strength training and attempting to alter the appearance of your body, you don’t want to place too much emphasis on the number on the scale, as it will not reveal all of your results.
“Rather than that, consider your entire body composition, including how your clothes fit and how your body will begin to feel and move differently,” Hagstrom noted.
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