Plain language summary
Exercise is an effective way to improve mental and physical health and can influence weight management due to the energy expenditure. Energy balance is influenced by day-to-day variations in energy intake and expenditure. The aim of this study was to address whether water-based exercise influences energy intake, appetite, and appetite related hormones differently to land based exercise in adults. This study is a systematic review and meta-analysis of nine studies which include randomised crossover ( 7 trials), semi-random (1 trial) (water-trial was required prior to iso-energetically matched water trial) and independent group (1 trial) (used in the 12-week study) designs. Results show that post-exercise energy intake is higher after water-based exercise versus a resting control. However, there wasn’t any difference in energy intake when water-based exercise was compared with land-based exercise. Furthermore, when different water temperatures were analysed, post-exercise energy intake was higher in cold water versus neutral water. Additionally, cycling and swimming did not alter fasting plasma concentrations of appetite regulating hormones (ghrelin and leptin), insulin or total peptide YY [gut hormone] but contributed to body mass loss. Authors conclude that if body mass management is a person’s primary focus, it is important to be mindful of the tendency to eat more in the subsequent hours after water-based exercise, as energy intake may be increased when compared to a no exercise control.
Expert Review
Conflicts of interest:
None
Take Home Message:
- The only type of exercise reporting an increase in energy intake was in water-based activities, where the temperature was between 18-20• C. However, this was only when explored in comparison to a resting control. No difference was reported in energy intake when water-based exercise was compared with land-based exercise.
- Any form of exercise, whether land or water-based should be considered where appropriate to reduce the risks of sedentary behaviour.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction:
Exercise is effective for weight-management alongside other physical and mental health benefits. Changes in appetite-regulating hormones may affect energy balance, e.g. some exercise may suppress appetite, known as exercise-induced anorexia. This review evaluated differences in energy intake, appetite and appetite-related hormones in land-based versus water-based exercise.
Methods:
The meta-analysis followed PRISMA guidelines and was registered on PROSPERO. Literature searching resulted in eight studies published between 1991 and 2021, which met the inclusion criteria (water v control), 5 studies (water v land) and 2 studies (water at different temperatures). Risk of Bias was assessed using Cochrane’s Risk of Bias for randomised trials.
Results:
Data were analysed in RevMan 5.4.1 using fixed effects, generic inverse variance method on energy intake. High heterogeneity prevented analysis on appetite and appetite-related hormones. Standard deviation was inputted based on estimated values for missing data. Heterogeneity was calculated using the I2 index. Sensitivity analyses were conducted. Statistical significance was set at p<0.05 and analyses based on two-tailed Z tests.
All participants had a healthy BMI, were aged 19-39 and ranged from well-trained to non-exercisers. A single bout of water-based exercise increased ad-libitum energy intake compared to a non-exercise control (mean difference [95% CI]: 330 [118, 542] kJ, P = 0.002) but no difference was identified between water and land-based exercise (78 [-176, 334] kJ, P = 0.55). Cold water exercise (18–20 •C) increased energy intake more than neutral water (27–33 •C) temperature (719 [222, 1215] kJ; P < 0.005). One 12-week study reported cycling and swimming did not alter fasting plasma concentrations of total ghrelin, insulin, leptin or total PYY but contributed to body mass loss 87.3 (5.2) to 85.9 (5.0) kg and 88.9 (4.9) to 86.4 (4.5) kg (P < 0.05) respectively.
Conclusion:
Despite limitations, this review may provide preliminary evidence on energy intake and appetite for water-based activities. If weight management is a primary focus, then water temperature needs to be considered, particularly if sub 20•C .
Clinical practice applications:
Although this study suggests cold water exercise may cause an increase in energy intake, 95% confidence intervals for individual studies are very large so results should be interpreted cautiously. Those preferring exercise in cold water, should be encouraged, providing they are mindful of the tendency to eat more post-exercise.
It is not possible to draw any robust conclusions about the ratings of hunger in response to different types of exercise due to limited data. However, according to the review, five studies demonstrated that hunger was suppressed more than control prior at the start of water-based exercise, and during and immediately after exercise.
Considerations for future research:
Most participants were of healthy weight and physically active, however since appetite signals may be dysregulated in obesity, including all weight categories and different activity levels may generate a more comprehensive overview.
Further research recommendations include:
- Measuring the effects of water- based activities on appetite, appetite related hormones and energy intake at different time points following exercise in order to provide recommendations for effective weight management strategies and in a range of different temperatures.
- Using a ‘no exercise’ water immersion control. Evidence suggests that immersion in cold water alone may increase energy expenditure
- Evaluating the effect of a water-based activity, such as swimming performed in a ‘fasted’ and ‘non-fasted’ state to investigate the impact on appetite, appetite related hormones and energy intake.
Abstract
Single bouts of land-based exercise suppress appetite and do not typically alter energy intake in the short-term, whereas it has been suggested that water-based exercise may evoke orexigenic effects. The primary aim was to systematically review the available literature investigating the influence of water-based exercise on energy intake in adults (PROSPERO ID number CRD42022314349). PubMed, Medline, Sport-Discus, Academic Search Complete, CINAHL and Public Health Database were searched for peer-reviewed articles published in English from 1900 to May 2022. Included studies implemented a water-based exercise intervention versus a control or comparator. Risk of bias was assessed using the revised Cochrane 'Risk of bias tool for randomised trials' (RoB 2.0). We identified eight acute (same day) exercise studies which met the inclusion criteria. Meta-analysis was performed using a fixed effects generic inverse variance method on energy intake (8 studies (water versus control), 5 studies (water versus land) and 2 studies (water at two different temperatures)). Appetite and appetite-related hormones are also examined but high heterogeneity did not allow a meta-analysis of these outcome measures. We identified one chronic exercise training study which met the inclusion criteria with findings discussed narratively. Meta-analysis revealed that a single bout of exercise in water increased ad-libitum energy intake compared to a non-exercise control (mean difference [95% CI]: 330 [118, 542] kJ, P = 0.002). No difference in ad libitum energy intake was identified between water and land-based exercise (78 [-176, 334] kJ, P = 0.55). Exercising in cold water (18-20 °C) increased energy intake to a greater extent than neutral water (27-33 °C) temperature (719 [222, 1215] kJ; P < 0.005). The one eligible 12-week study did not assess whether water-based exercise influenced energy intake but did find that cycling and swimming did not alter fasting plasma concentrations of total ghrelin, insulin, leptin or total PYY but contributed to body mass loss 87.3 (5.2) to 85.9 (5.0) kg and 88.9 (4.9) to 86.4 (4.5) kg (P < 0.05) respectively. To conclude, if body mass management is a person's primary focus, they should be mindful of the tendency to eat more in the hours after a water-based exercise session, particularly when the water temperature is cold (18-20 °C).
Lifestyle medicine
Fundamental Clinical Imbalances
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Hormonal
Methodological quality
Jadad score
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Not applicable
Allocation concealment
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Not applicable
