Water/aqua aerobics for 10 or more weeks at a time can trim waist size and aid weight loss, finds a pooled data analysis of the available evidence, published in the open access journal BMJ Open.

This type of exercise is particularly effective in overweight/obese women and the over 45s, the analysis indicates.

Global estimates for 2022 indicate that more than 43% of adults worldwide were overweight, and that 504 million women and 374 million men were obese, note the researchers, adding that obesity contributes to an estimated 2.8 million deaths every year.

The buoyancy of water helps reduce joint injuries commonly associated with land based exercise in those who are overweight or obese, explain the researchers. And while water/aqua aerobics are recommended for weight loss in this group, it’s not clear exactly what impact this type of exercise has on body composition, especially central obesity.

To find out, the researchers scoured research databases, looking for relevant studies published up to the end of 2021 that compared water/aqua aerobics with other types of exercise or nothing in adults who were overweight or obese, defined as a BMI of at least 30.

The results of 10 clinical trials in which the 286 participants (age range 20 to 70) were randomly assigned to an intervention were included in the pooled data analysis. The trials were carried out in Malaysia, Brazil, India, the USA, and the Netherlands. 

The types of water exercises included aerobics, zumba, yoga, and jogging, for periods of between 6 and 12 weeks across all included trials. Exercise frequency was mostly twice or three times a week, with most sessions lasting 60 minutes.

The analysis revealed that water/aqua aerobics was effective at reducing overall weight by an average of nearly 3 kilos and trimming waist circumference by 3 cm in participants who were obese or overweight.

A total of 10 studies including 286 obese or overweight individuals were included in this work and did not further differentiate between obese or overweight individuals.

But participating in water/aqua aerobics wasn’t associated with a reduction in BMI, percentage body fat, fat tissue, the midriff bulge (waist to hip ratio) or hip circumference.

Further detailed analysis of the results showed that exercise periods lasting more than 10 weeks (12 weeks) significantly reduced body weight by more than 3 kilos and waist circumference by nearly 3 cm in women and those aged 45 and older.

The results of this study only indicate that water aerobics have an effect on reducing waist circumference in both men and women, and further research is needed to determine whether they can be reduced to the normal waist circumference values for adult men and women.

There was little evidence of any impact on the body composition of men-although few men were included in the trials-nor those younger than 45.

The quality of evidence for each outcome was evaluated using the GRADE system, which rates the certainty of evidence in systematic reviews and other evidence syntheses. 

This indicated that the quality of evidence was moderate for body weight and waist circumference; low for BMI, lean mass, fat mass, waist to hip ratio and hip circumference; and very low for percentage body fat, primarily due to the small number of participants in whom this was assessed and that the design and methodology of the included studies varied considerably.

And the researchers acknowledge various limitations to their findings. Only studies published in English were considered and some included short (6 weeks) intervention periods and/or small numbers of participants.

But they suggest that, “the moderate certainty of evidence for [body weight] and [waist circumference] supports the use of [water aerobics] as an effective intervention for reducing overall body weight and central obesity, which are critical factors in managing obesity-related health risks.”

And they conclude: “Future research should aim to address these limitations by conducting larger, well-designed [randomised controlled trials] with standardised methodologies and diverse populations. Additionally, investigating the long-term effects of [water aerobics] and comparing its efficacy with other exercise modalities will provide valuable insights.”