A network meta-analysis conducted in 2019 investigated what exercise prescription is optimal to improve body composition and cardiorespiratory fitness in adults living with obesity.  The authors included 45 randomised control trials of which 21, with a total of 1689 participants demonstrated a non-statistically significant improvement in cardiorespiratory fitness as assessed by an increase in absolute VO2max. The authors noted that all exercise interventions brought about an increase in absolute VO2max of between 7% and 15% with a combination of high intensity aerobic and high-load resistance exercise most likely to increase in fitness and consequently recommended this as the preferential exercise intervention to improve cardiorespiratory fitness in this population.
Additionally, a metanalysis form 2017 sought to determine the effectiveness of high intensity interval training on cardiopulmonary fitness and body composition compared to traditional high volume continuous exercise.  18 studies with 854 participants were included and results showed that in the obese population training at high intensity is a better method to improve cardiopulmonary when compared to traditional lower intensity continuous exercise. (VO2max) (MD 1.83, 95% CI 0.70, 2.96, p<0.005; I2=31%). The authors did note that the overall quality of the included studies was low. Details about the randomization process and allocation concealment were lacking in almost all studies, so the risk of bias was unclear. Only 3 studies reported a blinded assessment of the outcomes. Also in 4 studies, the number of participants was low, ranging from
12-18, with the risk of overestimation or underestimation of the effect on outcome parameters.
Furthermore, a Systematic Review from 2013 included 14 trials (a metanalysis was not undertaken due to heterogeneity of the studies).  The review reported that energy restriction plus exercise training was more effective than energy restriction alone for improving cardiovascular fitness. Adding exercise training to energy restriction for obese middle-aged and older individuals results in favourable changes to fitness and body composition.
Quality of Evidence
A-Consistent evidence from meta-analysis and systematic reviews
Strength of recommendation
1-Small but significant benefit, low risk of physical activity
Exercise interventions probably result in an improvement in cardiopulmonary fitness as assessed by VO2 max. Exercise interventions that include high intensity interval training may have a greater improvement on cardiopulmonary fitness as assessed by VO2 Max than other interventions and can be recommended unless there are compelling reasons to do otherwise.
- O’Donoghue, Grainne, et al. “What exercise prescription is optimal to improve body composition and cardiorespiratory fitness in adults living with obesity? A network meta‐analysis.” Obesity Reviews 22.2 (2021): e13137.
- Türk, Y., Theel, W., Kasteleyn, M. J., Franssen, F., Hiemstra, P. S., Rudolphus, A., Taube, C., & Braunstahl, G. J. (2017). High intensity training in obesity: a Meta-analysis. Obesity science & practice, 3(3), 258–271. https://doi.org/10.1002/osp4.109
- Miller, Clint T., et al. “The effects of exercise training in addition to energy restriction on functional capacities and body composition in obese adults during weight loss: a systematic review.” PloS one 8.11 (2013): e81692.