Effects of high-intensity interval training on body composition, cardiorespiratory fitness, and selected lipid outcomes in adult women with overweight or obesity: a systematic review and meta-analysis

Figures

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  Figure 1. PRISMA 2020 flow diagram of the study selection process.

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  Figure 2. Traffic-light plot of study-level RoB 2 judgements for the included randomized controlled trials.

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  Figure 3. Distribution of study-level RoB 2 judgements across the included randomized controlled trials.

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  Figure 4. Forest plot of the effects of HIIT on body weight. Squares represent study-specific effect estimates, with the size of each square proportional to the study weight. Horizontal lines indicate 95% confidence intervals (CIs). The diamond represents the pooled effect estimate, and its width indicates the 95% CI. Effect sizes are expressed as Hedges’ g and were pooled using a random-effects restricted maximum likelihood (REML) model. Negative values favor HIIT for body weight reduction.

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  Figure 5. Bubble plots of the univariable meta-regression analyses for body weight. Panels show the associations between the effect size for body weight and age, baseline BMI, intervention duration, and training frequency. Each dot represents an individual effect size, and the shaded area indicates the 95% confidence interval (CI) around the fitted regression line. Effect sizes are expressed as Hedges’ g. The fitted lines suggest no clear evidence that age, baseline BMI, intervention duration, or training frequency was associated with the effect size of HIIT on body weight in the present analysis.

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  Figure 6. Forest plot of the effects of HIIT on body mass index. Squares represent study-specific effect estimates, with the size of each square proportional to the study weight. Horizontal lines indicate 95% confidence intervals (CIs). The diamond represents the pooled effect estimate, and its width indicates the 95% CI. Effect sizes are expressed as Hedges’ g and were pooled using a random-effects restricted maximum likelihood (REML) model. Negative values favor HIIT for reducing body mass index.

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  Figure 7. Bubble plots of the univariable meta-regression analyses for body mass index. Panels show the study-level associations between the BMI effect estimates and mean participant age, baseline BMI, intervention duration, and training frequency. Each dot represents an individual effect size, and the shaded area indicates the 95% confidence interval around the fitted regression line. Effect sizes are expressed as Hedges’ g. Baseline BMI and intervention duration showed statistically significant positive associations with the BMI effect estimate, whereas no clear evidence of an association was observed for mean participant age or training frequency. Because only 11 effect sizes were available and the analyses were based on study-level characteristics, these findings should be regarded as exploratory and should not be interpreted as causal.

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  Figure 8. Forest plot of the effects of HIIT on body fat percentage. Squares represent study-specific effect estimates, with the size of each square proportional to the study weight. Horizontal lines indicate 95% confidence intervals (CIs). The diamond represents the pooled effect estimate, and its width indicates the 95% CI. Effect sizes are expressed as Hedges’ g and were pooled using a random-effects restricted maximum likelihood (REML) model. Negative values favor HIIT for reducing body fat percentage.

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  Figure 9. Bubble plots of the univariable meta-regression analyses for body fat percentage. Panels show the study-level associations between the body fat percentage effect estimates and mean participant age, baseline BMI, intervention duration, and training frequency. Each dot represents an individual effect size, and the shaded area indicates the 95% confidence interval around the fitted regression line. Effect sizes are expressed as Hedges’ g. Training frequency showed a statistically significant negative association with the body fat percentage effect estimate. No clear evidence of an association was observed for mean participant age or intervention duration, while the positive association with baseline BMI did not reach statistical significance. Because only 10 effect sizes were available and the >3 sessions/week category contained only two effect sizes, these findings should be regarded as exploratory and should not be interpreted as causal.

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  Figure 10. Forest plot of the effects of HIIT on fat mass. Squares represent study-specific effect estimates, with the size of each square proportional to the study weight. Horizontal lines indicate 95% confidence intervals (CIs). The diamond represents the pooled effect estimate, and its width indicates the 95% CI. Effect sizes are expressed as Hedges’ g and were pooled using a random-effects restricted maximum likelihood (REML) model. Negative values favor HIIT for reducing fat mass.

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  Figure 11. Bubble plots of the univariable meta-regression analyses for fat mass. Panels show the study-level associations between the fat mass effect estimates and mean participant age, baseline BMI, intervention duration, and training frequency. Each dot represents an individual effect size, and the shaded area indicates the 95% confidence interval around the fitted regression line. Effect sizes are expressed as Hedges’ g. Baseline BMI showed a statistically significant positive association with the fat mass effect estimate, whereas training frequency showed a statistically significant negative association. No clear evidence of an association was observed for mean age, and the association with intervention duration did not reach statistical significance. Because only eight effect sizes were available and the distribution of training frequency was limited, these findings should be regarded as exploratory and should not be interpreted as causal.

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  Figure 12. Forest plot of the effects of HIIT on maximal or peak oxygen uptake. Squares represent study-specific effect estimates, with the size of each square proportional to the study weight. Horizontal lines indicate 95% confidence intervals (CIs). The diamond represents the pooled effect estimate, and its width indicates the 95% CI. Effect sizes are expressed as Hedges’ g and were pooled using a random-effects restricted maximum likelihood (REML) model. Positive values favor HIIT for improving maximal or peak oxygen uptake.