Aerobic exercise linked to reduced belly, body fat among those with obesity

Key takeaways:

• Increasing duration of aerobic exercise reduced body weight, waist size and body fat.
• Weekly aerobic exercise surpassing 150 minutes may be needed to achieve significant reductions, researchers said.

Aerobic exercise has been linked to reductions in several measures of body fat, including body weight and waist circumference, a systematic review and meta-analysis in JAMA Network Open found.

The findings add to data from previous studies on the extensive health benefits of aerobic exercise, which has also been tied to improvements in depression among adults with cancer and sleep following a concussion.

According to Ahmad Jayedi, PhD, a postdoctoral research associate at Imperial College London, and colleagues, evaluating the possible dose-response links between aerobic exercise and adiposity markers “is of clinical and public health importance because it can determine how body weight, waist size, and fat change with increasing aerobic training dose, thereby contributing to providing useful information needed for decision-making.”

In the analysis, the researchers assessed 116 randomized clinical trials that had aerobic exercise intervention durations of at least 8 weeks and involved 6,880 participants (mean age, 46 years; 61% women) with overweight or obesity.

Changes in waist circumference, body weight and body fat served as the study’s primary outcomes, while secondary outcomes included changes in medication use, adverse events and health-related quality of life.

Jayedi and colleagues found that every 30 minutes of aerobic exercise a week corresponded with a:

• 0.52 kg reduction in body weight (95% CI, 0.61 to 0.44);
• 0.56 cm reduction in waist circumference (95% CI, 0.67 to 0.45); and
• 0.37% reduction in body fat percentage (95% CI, 0.43% to 0.31%).

This evidence ranged from moderate to high certainty.

Every 30 minutes of aerobic exercise per week was also associated with decreases in areas of visceral (mean difference [MD] = 1.6 cm²; 95% CI, 2.12 to 1.07) and subcutaneous (MD = 1.37 cm²; 95% CI, 1.82 to 0.92) adipose tissues.

Waist circumference and body weight decreased monotonically or linearly in association with 150 to 300 minutes of aerobic exercise per week at varying intensities.

For example, researchers reported reductions in weight loss of 2.79 kg (95% CI, 3.29 to 2.29) and 4.19 kg (95% CI, 5.98 to 2.41) at 150 and 300 minutes of aerobic exercise a week, respectively, along with decreases in waist circumference of 4.21 cm (95% CI, 6.85 to 1.58) at 300 minutes per week of aerobic exercise at moderate intensity and 5.34 cm (95% CI, 9.05 to 1.63) at 300 minutes per week of aerobic exercise at moderate to vigorous intensity.

The analysis showed the largest decrease in body fat percentage at 150 minutes of aerobic exercise a week (MD = 2.08%; 95% CI, 2.47% to 1.69%), with similar findings observed for body fat mass.

The researchers pointed out that aerobic exercise further modestly increased physical (standardized MD = 1.69 standard deviation [SD]; 95% CI, 1.18-2.2) and mental (standardized MD = 0.74 SD; 95% CI, 0.29-1.19) quality of life, but this evidence was of low certainty.

Aerobic exercise additionally increased mild to moderate adverse events, which were usually musculoskeletal symptoms, and was not tied to changes in medication use.

Jayedi and colleagues noted that only two studies had intervention durations longer than 48 weeks, which “raises concerns about the association of aerobic exercise with weight loss beyond 1 year.”

Ultimately, “aerobic training exceeding 150 minutes per week at moderate intensity or greater may be needed to achieve associations with clinically important reductions,” they concluded.