We have seen that exercise has a small but meaningful impact on body size in participants wishing to lose weight. A recent systematic review and meta-analysis (Jayedi et al. 2024) looked at the relationship between exercise and Body Mass Index (BMI), waist circumference and body fat. The researchers restricted their analysis to randomised controlled studies (RCTs) with a minimum duration of eight weeks and supervised aerobic exercise.
The researchers included data from 116 studies with 6,880 participants from around the world. All the participants were obese or overweight. The reduction in body weight was linear as exercise duration increased up to 300 minutes per week. Similar relationships were seen for waist circumference and body fat. A minimum of 150 minutes of exercise per week was required to make clinically significantly changes.
It was found that each 30 minute period of exercise per week over an 8-24 week follow-up period was associated with a reduction in body weight of 0.52Kg, a reduction in waist circumference of 0.56 cm and a lower body fat percentage (-0.37%).
This review focused purely on exercise and it is a limitation of the base data that the researchers were not able to consider whether changes in diet played a role alongside the aerobic exercise programme.
Jayedi A, Soltani S, Emadi A, Zargar MS, Najafi A. Aerobic Exercise and Weight Loss in Adults: A Systematic Review and Dose-Response Meta-Analysis. JAMA Netw Open. 2024 Dec 2;7(12):e2452185. doi: 10.1001/jamanetworkopen.2024.52185. PMID: 39724371; PMCID: PMC11672165.