Participation in either strength training or aerobic exercise is associated with a lower prevalence of obesity, but combining both is the most effective way to reduce the likelihood of becoming obese, researchers say.
In a large survey of roughly 1.7 million US adults, those who met both aerobic and muscle-strengthening exercise guidelines — which call for ≥ 150 minutes of moderate aerobic exercise and at least two muscle-strengthening exercises per week — had a lower prevalence of obesity than those who did not.
Of interest, the survey also showed that the greater the level of obesity, the larger the benefit that was derived from combining both modalities, said lead author Jason A. Bennie, PhD, of the University of Southern Queensland Physically Active Lifestyles (USQ PALs) research group, Australia. The findings were published online in Obesity.
“I am a behavioral physical activity epidemiologist and my area of interest is in physical activity and chronic disease,” Bennie told Medscape Medical News.
“Both aerobic and muscle-strengthening exercise are recommended for obesity prevention, but it is not known which modality is most effective at the population level,” he explained.
“Most of the evidence around health is based on aerobic exercise like walking, cycling, and jogging. But in this particular study, I was interested in looking at the association between different combinations of strength training and aerobic exercise and how they affected weight,” he said.
In an accompanying editorial, Timothy S. Church, MD, PhD, Pennington Biomedical Research Center, Baton Rouge, Louisiana, notes: “This is by far the largest study to ever examine the combination of aerobic and strength training, and it provides further evidence for the value of combining the two exercise modalities.”
“Epidemiologists Like Big Data”
Bennie and colleagues say the independent and/or combined associations of moderate to vigorous physical activity (aerobic exercise) and muscle-strengthening exercise with obesity at the population level are largely unknown.
“To our knowledge, this is the first population-level study examining the associations between muscle-strengthening exercise, combined moderate to vigorous physical activity and muscle-strengthening exercise, and obesity,” they write.
Bennie and his team pooled data on 1,677,108 adults age 18 years and older from four US Behavioral Risk Factor Surveillance System (BRFSS) surveys for 2011, 2013, 2015, and 2017.
“This is a big survey which is run every year in the United States, but every second year they include a physical activity component. I pulled all the data on people’s physical activity and how this was associated with their body mass index (BMI). The reason why we chose US data is because the United States has a good surveillance system to monitor their population,” Bennie said.
And “epidemiologists like big data,” he observed.
Just over one fourth of respondents were ≥ 65 years, 51.6% were female, and most were white or Hispanic.
Over half had never smoked, and 18.6% reported “excellent” health.
To determine exercise habits, physical activities were coded as “aerobic” or “nonaerobic” using a list of 56 activities, with examples of aerobic activities including walking, jogging, tennis, and soccer. To assess strength training, participants were asked: “Do not count aerobic activities like walking, running, or bicycling. Count activities using your own body weight like yoga, sit-ups, or push-ups, and those using weight machines, free weights, or elastic bands.”
Forty percent of respondents reported they did not meet guidelines for aerobic or strength-training exercise, 9.5% met strength-training guidelines only, 30.2% met aerobic guidelines only, and 20.2% met guidelines for both.
Overall, 35.6% had a BMI of 18.5-24.9 kg/m2 (healthy weight), and 28.9% had a BMI of ≥ 30 kg/m2 (obese).
Obese respondents were further categorized into the following three classes:
Class I obesity and above (BMI ≥ 30.0 kg/m2 but < 35.0 kg/m2)
Class II obesity and above (BMI ≥ 35.0 kg/m2 but < 40.0 kg/m2)
Class III obesity and above (BMI ≥ 40.0 kg/m2)
Associations Were More Pronounced for Higher Obesity Classes
Analysis of the data showed that respondents who met both exercise guidelines had the lowest adjusted prevalence ratios (APRs) for obesity across all classes of obesity compared with those in the other exercise categories. Their APRs ranged from 0.27 to 0.50.
Interestingly, noted Bennie, the prevalence ratios (PRs) were lowest for all physical activity categories for those with Class III obesity.
Adjusted Prevalence Ratios (APRs) for Meeting Both Exercise Guidelines
| Obesity Class | APR | 95% CI |
|---|---|---|
| Class I obesity and above (BMI ≥ 30.0 kg/m2) | 0.54 | 0.53 – 0.54 |
| Class II obesity and above (BMI ≥ 35.0 kg/m2) | 0.32 | 0.31 – 0.33 |
| Class III obesity and above (BMI ≥ 40.0 kg/m2) | 0.21 | 0.20 – 0.21 |
The associations remained after adjusting for gender, socioeconomic status, education, lifestyle characteristics, and chronic health conditions, Bennie said.
“The bottom line is that it is the combination of both weight training and aerobics that is the most effective for reducing the likelihood of obesity,” he stressed.
“The real problem is that once you get into the higher levels of obesity, it is very difficult to go back into normal weight. It’s a very slippery slope. We need to help stop people from getting into those higher levels of obesity, when things really start going awry with their metabolism, their blood glucose, their depression,” he emphasized.
“While prospective studies and controlled designs are needed to better support causal evidence, this study suggests that a combination of moderate to vigorous physical activity and muscle-strengthening exercise has the most beneficial associations with overall obesity and obesity severity,” Bennie and colleagues reiterate.
Emphasize Importance of Combining Aerobic and Strength Training
In his editorial, Church notes that “while cross-sectional designs do not allow for cause-and-effect determination, this manuscript is still a valuable contribution to the literature.”
He emphasizes that BMI does not differentiate fat mass from lean muscle mass, and the fact that strength training promotes muscle mass creates the opportunity for misclassification, “yet the weight training was still found to be associated with a lower risk of obesity as defined by BMI.”
“In my experience, few individuals are aware of the strength training recommendations. This is unfortunate, as the evidence is clear that while strength training has health benefits, aerobic training has more; however, doing both is optimal,” he adds.
This study “provides further evidence of the need for emphasis on the importance of including strength training in one’s physical activity program.”
“For those individuals focused on preventive measures to promote healthy aging, the importance of combining aerobic and strength training exercise needs to be emphasized,” he concludes.
Bennie and Church have reported no relevant financial relationships.
Obesity 2020;28:224,371-378. Full text, Editorial
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