Effects of exercise with or without a hypocaloric diet on intermuscular and intramuscular fat: a systematic review

Background: Intermuscular (InterMAT) and intramuscular (IntraMAT) adipose tissues are key contributors to skeletal muscle function and metabolic health. Objective: In this systematic review, we aimed to investigate the impact of different types of exercise with or without a hypocaloric diet on reducing InterMAT and IntraMAT in various muscle tissues. Method: A literature search was performed via PubMed, Cochrane Library, Scopus, and Web of Science from inception until February 2025. Eligible RCTs examined the effects of exercise compared to control in adults > 18 years. A narrative synthesis was employed with a registered protocol at CRD42024511531. Results: Nineteen RCTs were included in the systematic review. Resistance and aerobic exercise alongside a hypocaloric diet displayed inconsistent results in reducing thigh InterMAT. Under non-hypocaloric conditions there were consistently no alterations of InterMAT and IntraMAT irrespective of muscle tissue. When concurrent exercise was followed, no statistically significant changes were observed with or without a hypocaloric diet on thigh InterMAT and IntraMAT. Results were overall lacking in regards to resistance or aerobic exercise and IntraMAT due to the low number of studies. Conclusion: There is potential in reducing thigh InterMAT following resistance or aerobic exercise combined with a hypocaloric diet, although inconsistencies among studies were presented. However, irrespective of exercise type, under non-hypocaloric conditions no benefits were conferred on InterMAT and IntraMAT of any muscle tissue. Further research is warranted to determine the effects of different exercise intensities employing an adequate dietary and hypocaloric control on skeletal muscle InterMAT and particularly IntraMAT.