Both groups will be asked to ensure that they consume at least two servings (330 ml) of their elected beverages dependent on condition (NNS vs. water). All beverages will be picked by participants (from a permitted range) and then delivered to them in bi-weekly batches using an online delivery-style system. Primary study visits for body weight, waist circumference, hip circumference, sagittal diameter, and blood pressure assessments will be carried out at various stages throughout the trial. Initial assessments will be at baseline (week -2), monthly over the weight loss period (weeks 4, 8 and 12), monthly over the assisted weight maintenance period (weeks 16, 20, 24, 28, 32, 36, 40, 44 and 48) and at a 1 year post assisted weight maintenance visit with Subset 2 additionally providing body composition (DXA) scans at baseline, at the end of the weight loss period, at the end of the assisted weight maintenance period and at a 1 year post assisted weight maintenance visit. During the weight loss phase, participants will meet in groups (10-12 participants) with a dietician-trained researcher every week (12 visits) followed by monthly meetings during the assisted weight maintenance phase (9 visits). Participants will additionally be asked to complete a series of questionnaires throughout the intervention period and complete a series of diet diaries (3-day diet diaries and food frequency questionnaires; FFQs) to assess compliance throughout the trial. Furthermore, empty product packaging (labels or bottles) will be collected as an additional compliance measure. The probe days to be completed by Subset 1 will involve participants attending the Study Centre at various times over an 8-hour day period for 3 meals (breakfast, lunch and dinner) and 1 drink (NNS, sugar sweetened beverage (SSB) or water) for a total of 15 sessions. Adverse events and concomitant medicine will be registered continuously throughout the study in relevant forms. For each participant, the total study duration is 100 weeks (not including recruitment and screening) and includes a total of 39 visits (with additional visits for Subsets 1 and 2).