Research Spotlight: Can strength training help you lose weight?

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A recent study in PLOS Medicine, researchers in the US discovered that as little as 1-2 hours of resistance exercise per week was strongly associated with a reduced risk of obesity. In fact, those who completed resistance training were 20 per cent to 30 per cent less likely to become obese over time than people who do not, regardless of whether they also completed aerobic exercise.

2 in 3 Australian adults, or around 12.5 million indiviuals, are either overweight or obese. According to the Australian Institute of Health and Welfare, 8.4% of the total burden of disease was due to overweight and obesity and it is projected that by 2025 around 83% of Australian men and 75% of women aged 20 years and over will be overweight or obese.

While we know that modest weight loss (approx 5% of body weight) is associated with significant improvements in health, unfortunately around 50% of individuals who lose more than 5% of their body weight keep it off for more than 5 years. This highlights the difficulty in losing weight overtime and the importance of preventing obesity in the first place.

There is currently a strong evidence that aerobic exercise, such as running and swimming, helps to prevent obesity. However, there has been far less research into the relationship between resistance exercise and the risk of developing obesity. Researchers at the University of Iowa sought to determine what effect resistance exercise had on preventing obesity, after accounting for participating in aerobic exercise.

Researchers gained access to information from the Aerobics Center Longitudinal Study which recorded exercise and health data from over 15,000 individuals across 18 years. The Iowa researchers analysed nearly 12,000 individuals without obesity and followed their exercise participation over 6 years. They not only measured participants BMI to determine obesity, they also looked at waist circumference and body fat percentage.

From the group of 12,000 individuals, only 29% performed resistance exercise consistently across the 6 years. However, researchers found those who did participate in resistance exercise at least 2 days per week had reduced their risk of developing obesity by 18% (when measuring BMI), 30% (when measuring waist circumference) and 30% when measuring body fat percentage.

These benefits remained even when adjusting for gender, age, smoking status, alcohol consumption and certain health conditions.

What makes this study even more interesting is that these benefits were seen even for those who did little to no aerobic exercise. The study showed that aerobic and resistance exercise together had the lowest risk of developing obesity, however those who participated in only resistance exercise had a lower risk of developing obesity than those who only participated in aerobic exercise.

This study notes that there is still little research into exactly how resistance exercise helps to prevent obesity, however we know that resistance exercise increases basal metabolic rate for up to 24 hours after an exercise and that resistance exercise may stimulate muscle hypertrophy, which has been found to cause reductions in fat mass.

Overall, the study shows that while aerobic exercise is beneficial in helping to prevent unnecessary weight gain, resistance exercise is crucial in helping to prevent obesity as we age.

Brellenthin AG, Lee DC, Bennie JA, Sui X, Blair SN. Resistance exercise, alone and in combination with aerobic exercise, and obesity in Dallas, Texas, US: A prospective cohort study. PLoS Med. 2021 Jun 23;18(6):e1003687. doi: 10.1371/journal.pmed.1003687. PMID: 34161329; PMCID: PMC8266085.