The effects of detraining on body composition and cardiometabolic health: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Structured exercise interventions can significantly improve body composition and cardiometabolic health. However, a comprehensive synthesis of evidence regarding the effects of stopping training on body composition and cardiometabolic health outcomes remains lacking. OBJECTIVE: This systematic review and meta-analysis aimed to evaluate the effect of detraining after exercise on body composition and cardiometabolic health. METHODS: PubMed, Web of Science, Embase, SPORTDiscus, MEDLINE, and CINAHL were searched. Randomized controlled trials that involved an exercise and detraining phase were included. Risk of bias was assessed using Cochrane RoB2. A meta-analysis was performed to estimate effect sizes comparing pre-intervention to post-intervention and pre-intervention to post-detraining for body composition and cardiometabolic health outcomes. Subgroup analyses were stratified into short-term (≤ 2 months), medium-term (2-6 months, including 6 months), and long-term (> 6 months) intervals. RESULTS: 86 studies (n=5,670) were included. Meta-analysis indicated that after exercise withdrawal, overall reductions in Waist-to-Hip Ratio (WHR), mean arterial pressure (MAP), and fasting blood glucose (FBG) relative to baseline remained significant, and the homeostasis model assessment of insulin resistance (HOMA-IR) remained borderline significantly reduced. By detraining duration, compared with baseline, body mass, waist circumference, and maximal oxygen uptake remained significantly improved relative to baseline in the short-, medium-, and long-term subgroups; Body mass index, peak oxygen uptake, and fat mass remained significantly improved in the short- and medium-term subgroups; Systolic blood pressure remained significantly decreased in the short- and long-term subgroups; Body fat percentage remained significantly decreased in the short-term subgroup and was borderline significantly improved in the medium-term subgroup; Diastolic blood pressure, MAP, and triglycerides remained significantly improved in the short-term subgroup. High-density lipoprotein cholesterol remained significantly improved in the short-term subgroup; FBG, HOMA-IR, and fasting insulin remained significantly improved in the short-term subgroup; Fat-free mass remained significantly decreased in the medium-term subgroup; WHR, muscle mass, lean body mass, skinfold thickness, resting heart rate, and low-density lipoprotein cholesterol were no longer significant in any of the follow-up subgroups. CONCLUSIONS: Exercise-induced health benefits may not immediately return to baseline levels after detraining and may exhibit residual effects in an outcome-specific and time-dependent manner. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420251149494.