Subsets Subset 1 - Appetite Probe Days A voluntary subset of randomly selected participants (n=116) will be invited to participate in the appetite probe day sessions to assess changes in appetite response to caloric and non-caloric beverages (water, NNS and caloric beverages; CB). These probe days will be measured at baseline (Visits 2a, 2b & 2c; weeks -2 to 0), at the start of the weight loss programme (Visits 3a, 3b and 3c; weeks 1 to 2), at the end of the weight loss period (Visits 13a, 13b and 13c; weeks 11 to 12) at the end of the assisted weight maintenance period (Visits 24a, 24b, 24c; weeks 47 to 48) and at the end of the 1 year post assisted weight maintenance period (Visits 38a, 38b, & 38c). These sessions will be scheduled a minimum of 3 days after one another (minimum completion of 2 weeks) and must all be completed within a maximum of 3 weeks. At each point one probe day will examine the response to a caloric beverage (ie a sugar sweetened beverage; SSB) and then the second and third the response to NNS and water (the order of all three drinks will be counterbalanced across participants and probe days). These will be provided after breakfast and 1 hour before lunch (approximately 12pm). Compensation will then be tracked at an ad libitum test lunch and an evening meal. Participants will be blinded to the study condition (no information will be provided about the drinks during the probe days) however the sensory characteristics of the beverages may be evident. Cognitive and sensory cues cannot be matched but are important determinants of real world appetite responses.