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Background: Time-restricted eating (TRE) has been suggested to be a simple, feasible, and effective dietary strategy for individuals with overweight or obesity. We aimed to investigate the effects of 3 months of 10-h per-day TRE and 3 months of follow-up on bodyweight and cardiometabolic risk factors in individuals at high risk of type 2 diabetes., Methods: This was a single-centre, parallel, superiority, open-label randomised controlled clinical trial conducted at Steno Diabetes Center Copenhagen (Denmark). The inclusion criteria were age 30-70 years with either overweight (ie, BMI ≥25 kg/m 2 ) and concomitant prediabetes (ie, glycated haemoglobin [HbA 1c ] 39-47 mmol/mol) or obesity (ie, BMI ≥30 kg/m 2 ) with or without prediabetes and a habitual self-reported eating window (eating and drinking [except for water]) of 12 h per day or more every day and of 14 h per day or more at least 1 day per week. Individuals were randomly assigned 1:1 to 3 months of habitual living (hereafter referred to as the control group) or TRE, which was a self-selected 10-h per-day eating window placed between 0600 h and 2000 h. Randomisation was done in blocks varying in size and was open for participants and research staff, but outcome assessors were masked during statistical analyses. The randomisation list was generated by an external statistician. The primary outcome was change in bodyweight, assessed after 3 months (12 weeks) of the intervention and after 3 months (13 weeks) of follow-up. Adverse events were reported and registered at study visits or if participants contacted study staff to report events between visits. This trial is registered on ClinicalTrials.gov (NCT03854656)., Findings: Between March 12, 2019, and March 2, 2022, 100 participants (66 [66%] were female and 34 [34%] were male; median age 59 years [IQR 52-65]) were enrolled and randomly assigned (50 to each group). Of those 100, 46 (92%) in the TRE group and 46 (92%) in the control group completed the intervention period. After 3 months of the intervention, there was no difference in bodyweight between the TRE group and the control group (-0·8 kg, 95% CI -1·7 to 0·2; p=0·099). Being in the TRE group was not associated with a lower bodyweight compared with the control group after subsequent 3-month follow-up (-0·2 kg, -1·6 to 1·2). In the per-protocol analysis, participants who completed the intervention in the TRE group lost 1·0 kg (-1·9 to -0·0; p=0·040) bodyweight compared with the control group after 3 months of intervention, which was not maintained after the 3-month follow-up period (-0·4 kg, -1·8 to 1·0). During the trial and follow-up period, one participant in the TRE group reported a severe adverse event: development of a subcutaneous nodule and pain when the arm was in use. This side-effect was evaluated to be related to the trial procedures., Interpretation: 3 months of 10-h per-day TRE did not lead to clinically relevant effects on bodyweight in middle-aged to older individuals at high risk of type 2 diabetes., Funding: Novo Nordisk Foundation, Aalborg University, Helsefonden, and Innovation Fund Denmark., Competing Interests: Declaration of interests JSQ has received funding for this study from the Novo Nordisk Foundation, Innovation Foundation, and Aalborg University; for other studies from Novo Nordisk; and travel grants from American Diabetes Association, European Association for the Study of Obesity, and Trygfonden Center for Physical Activity Research. HEP is currently employed by Novo Nordisk and is co-investigator on a project partly funded by the Novo Nordisk Foundation and Innovation Fund Denmark. SP is the author of the books The Circadian Code and The Circadian Diabetes Code, which advocate for time-restricted eating. DV is currently employed by Novo Nordisk and has received research grants from Bayer, Sanofi Aventis, Novo Nordisk, and Boehringer Ingelheim and holds shares in Novo Nordisk. SST has received research grants for a study drug and lecture fees from Novo Nordisk. KKBC is currently employed by Novo Nordisk; holds shares in Novo Nordisk; and was co-investigator on this project, for which her salary was covered by a grant from the Novo Nordisk Foundation. MEN has received research grants from Bayer. NJWA has received research grants from Novo Nordisk and Mercodia and has received speaker fees and fees as a member of the advisory board from Merck, Guidepoint, and Boehringer Ingelheim. JJH has received research grants from Novo Nordisk Foundation, Arla Foods, and European Research Council; consulting fees from Alphasights, Arix Bioscience, Eli Lilly, Structure Therapeutics USA, Zealand Pharma, Alcimed, Google Ventures Management, MSD Danmark, and Novo Nordisk; and support for presentations from Eli Lilly, Zealand Pharma, Novo Nordisk, and the Mayo Clinic. MEJ holds shares in Novo Nordisk. JS holds shares in Novo Nordisk. KF is currently employed by Novo Nordisk and has received research grants from Novo Nordisk, Unilever, and AstraZeneca and holds shares in Novo Nordisk and ChemoMetec. MMJ received funding from the Danish Association for the Study of Obesity; is a co-investigator on a project funded by Novo Nordisk; and was co-investigator on this project, for which her salary was covered by grants from the Novo Nordisk Foundation and Aalborg University. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.)