INTRODUCTION: In pregnancy, people with obesity or excess adiposity are prone to excess gestational weight gain (GWG) and have the highest risks for multiple maternal morbidities. Epidemiological studies suggest that the lowest incidence of adverse maternal and infant outcomes occurs with GWG lower than current recommendations (<
5 kg) and with gestational weight maintenance, resulting in fat mass loss, in those with obesity. Data from randomised clinical trials are needed to evaluate the efficacy of a fat mass loss intervention on pregnancy outcomes. The objective of this proof-of-principle randomised controlled trial is to test the effect of a gestational fat mass loss intervention in pregnant individuals with obesity on changes in weight, fat mass and cardiometabolic disease risk factors. METHODS AND ANALYSIS: In this two-site randomised parallel group, 100 women (30% black
30% Hispanic) with pre-existing obesity (31.0≤body mass index≤55.0 kg/m ETHICS AND DISSEMINATION: The trial has been approved by the Pennington Biomedical Research Center Institutional Review Board, is monitored by an independent data and safety monitoring board and will be conducted in agreement with the Declaration of Helsinki. All results, positive, negative and inconclusive, will be disseminated at national and/or international scientific meetings and in peer-reviewed scientific journals. TRIAL REGISTRATION NUMBER: NCT04731688.