Think only aerobic exercise burns fat? Think again! A new systematic review and meta-analysis out of the University of South Wales suggests that this isn’t necessarily the case.
In fact, strength training is just as effective as aerobic exercise when it comes to shedding unwanted body weight.
The study shows that we can lose around 1.4% of our entire body fat through strength training alone, which is very close to how much we can lose through cardio or aerobics.
Strength training and fat loss
“A lot of people think that if you want to lose weight, you need to go out and run,” says Dr Mandy Hagstrom, exercise physiologist and one of the senior authors of the study.
“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 link between strength training and fat loss has been largely unclear up to this point. Studies have investigated this link in the past, but their sample sizes have tended to be small, reducing their validity.
“It can be really difficult to discern whether there’s an effect or not based on one study alone,” adds Dr Hagstrom. “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.”
Dr Hagstrom and the research team brought together 58 research papers that used highly accurate forms of body fat measurement (such as DEXA body scans, which can distinguish fat from lean mass) to measure the results of strength training programs. These studies included about 3000 participants, none of whom had any previous strength training experience.
As we might expect, the programs differed between the studies, but all of the 3000 participants worked out for roughly 45-60 minutes each session, for an average of 2.7 times per week. The programs lasted for about five months.
Why do so many people think aerobic training is the way to go when it comes to losing fat?
Part of the reason is because many people aren’t measuring their weight loss correctly.
If all you do is focus on the number on the scale, this can be extremely misleading. Importantly, the number doesn’t tell you the composition of your body (i.e. how much fat, how much water, how much bone, how much lean tissue).
“More often than not, we don’t gain any muscle mass when we do aerobic training,” says Dr Hagstrom. “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.”
To ensure that they took body composition changes properly into account, the research team focused on measuring how much the total body fat percentage changed after strength training programs.
“A lot of fitness recommendations come from studies that use inaccurate measurement tools, like bioelectrical impedance or scales,” says Dr Hagstrom.
“But the most accurate and reliable way of assessing body fat is through DEXA, MRI or CT scans. They can compartmentalise the body and separate fat mass from lean tissue.”
Although their study didn’t show the effects of other variables like exercise duration, frequency, intensity, or set volume, the team are now hoping to investigate whether changing these variables can change the amount of fat loss.
Strength training and long-term weight loss
We’ve already written at length about how strength training is a much better way to ensure long-term health and fitness than exhausting cardio sessions.
In the article linked above, we wrote:
Although cardiovascular exercise will burn more calories in the short-term than weights-based exercise, strength training helps to retain muscle mass in the face of aging, which appears to be the crucial factor in this long-term study. After the age of 30, muscle mass gradually decreases, reducing the body’s basal metabolic rate – its basic daily energy need – thereby making it easier to put on weight as time passes. Cardiovascular exercise does little to build muscle, and in excess can actually lead to muscle loss.
A long-term study of 10,000 men showed that older men who performed resistance exercise stayed in much better shape than those who performed cardio.
The researchers used longitudinal data on more than 10,000 healthy men for a period between 1996 and 2008, charting how the men’s waist measurements had changed over those 12 years. All of the participants in the study were between 40 and 75 when the study first began.
“Because aging is associated with the loss of skeletal muscle mass, relying on body weight is insufficient for the study of healthy aging”, stated the lead author of the study. “Measuring waist circumference is a better indicator of healthy body composition among older adults.”
The men were divided up according to the amount of aerobic exercise they did, and then according to the amount of strength training they did.
The results clearly show that those who also did strength training saw a much greater decrease in relative waist circumference, with the result for those performing more than 25 minutes a day being especially striking. The relative waist circumference change was actually most for those who performed 25 minutes a day of strength training but did not adhere to the aerobic-exercise recommendations.
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