The study aims to investigate body-weight and behavioural trajectories, as well as their underlying individual, social, and environmental determinants from University to early working life. The study employs mHealth approaches in the form of a smartphone app and smart wearables to collect health behaviour and related information to answer the following research questions:

1. To what extend do health behaviours (activity, diet, and sleep), body weight, and mental well-being change during the transition from university to early working life?
2. What is the relationship between health behaviours and mental well-being, and how does it differ at different stages of the transition from University to early working life?
3. What are the determinants of physical activity, healthy eating and sleep in university students and young working adults?
4. Do these determinants differ at different stages of the student to work life transition?
5. If so, how do these differences in these determinants relate to changes in health behaviours, weight status, and mental well-being?

This is a prospective cohort study. The study period for each participant is 2 years. Participants are required to download the study's smartphone app and wear the assigned smartwatch to collect various information (including step counts and sleep time). Physical measurements are taken in person at baseline, 12 months and 24 months visits. These measurements include height, weight, waist circumference, resting heart rate and blood pressure.

Questionnaires administered at baseline, 12 months and 24 months include:

• Demographics (age, gender, religion, socio-economic status, education level)
• Personality
• Dietary intake and habits
• Physical activity, sedentary behavior and screen time
• Active and passive transport use
• Smoking habit
• Sleep quality
• Mental health and wellness
• Medical history
• Women's health-related

Participants will also receive occasional surveys sent to their smartphone through the study app. These surveys will include questions about sleep, diet, technology use, binge drinking, smoking, physical activities and/or emotions.

Inclusion Criteria:

• Full time National University of Singapore students (undergraduate and postgraduate)
• Singapore Citizen or Permanent Resident;
• Has a Singapore registered mobile number• Owns a mobile phone with operating system that is compatible with the study app (iOS 10 or Android 7 and above);
• Able to make the upfront deposit of $20 and able to set up the Direct Debit Authorization (DDA) for possible deductions by HPB;
• Able to understand the study procedure during the informed consent taking process.

Exclusion Criteria:

• Students who will be overseas for more than 6 weeks per trip during the study period (e.g. involved in overseas exchange/internship programmes or stationed overseas) or travelling frequently;
• Students who are not able to set up the DDA via online method will be excluded;
• Students who has worked in a full-time position for more than a year previously;
• Pregnant women will be excluded only at the point of recruitment.

This is a cohort of National University of Singapore (NUS) (undergraduate and postgraduate) students.