The aim of this study is to implement an exploratory pilot trial of "My Meal Mate" (MMM), a smartphone application developed to facilitate weight loss, assessing its feasibility and acceptability. Overweight and obese adults will be recruited from large employers within the local area. The trial will aim to recruit a sample size of 135 which is a pragmatic decision based on randomizing 45 people to each arm. Participants will be randomized to one of three groups. The researchers have developed a smartphone application for weight loss called "My Meal Mate" (MMM) which incorporates a large branded food and drink database. MMM was developed using focus group data collected from potential system users and by benchmarking with similar commercially available diet tracking applications. One group will receive a smartphone with the MMM app downloaded on it, one group will receive access to an online food diary and one group will be given a paper food diary. Participants will be asked to set a goal for weight loss and self-monitor their food intake and activity using their allocated study equipment. Participants will be weighed at the beginning of the trial, at 6 weeks and at 6 months. Feasibility and acceptability outcomes will be assessed.

Inclusion Criteria:

• Aged 18-65
• BMI equal to or greater than 27 kg/m2
• Willing to commit the necessary time and effort to the study,
• Employed by a large employer in Leeds (and expects to continue to be employed there for the next 12 months),
• Able to read and write in English,
• Able to access the internet,
• Willing to be randomised to one of three groups.

Exclusion Criteria:

• Pregnant, planning a pregnancy within next 12 months, lactating
• Has had surgery for weight loss
• Taking the medication sertraline (due to associations with weight gain)
• Taking anti-obesity medications or medications for diabetes