The decision to end recruitment early is based on challenges encountered in the recruitment process that have hindered progress toward study goals.

Inactivity is the fourth leading risk factor for global mortality, leading to chronic diseases. Much of the world's population is inactive, and older adults are at highest risk. Incentive-based interventions show promise for improving activity levels. The investigators propose to conduct a study to evaluate the impact of incentives on physical activity of older adults (55 and above). Half the participants will receive additional incentives for walking throughout the study. Their step count and physical/mental health will be compared to a control group. The investigators will track the physical activity of participants using Fitbits and will encourage physical activity through making meal donations on behalf of participants (prosocial incentives) and giving them gift cards that can be redeemed at local businesses (personal incentives). Physical and mental health before and after the study will also be assessed using a written survey.

Inactivity is the fourth leading risk factor for global mortality, leading to chronic diseases (e.g., heart disease, diabetes) and contributing to the obesity epidemic. Much of the world's population is inactive and older adults are at highest risk. Inactivity in older adults is linked to age-related diseases and cognitive decline. Inactivity also imposes social costs through increased medical expenses, which are already high among the growing older adult population in the US.

Incentive-based interventions have gained popularity among behavioral scientists and policymakers as a tool for improving health-related behaviors. But there are drawbacks - first, monetary incentives are often not cost-effective, and therefore scalability is limited. Second, behaviors often return to baseline when monetary incentives are removed, i.e., healthy habits are hard to maintain when incentives are limited in duration. Third, there is a concern that monetary incentives crowd out intrinsic motivation to engage in health-promoting behaviors.

In light of the limited success of incentive-based behavior change programs, the investigators propose to design and evaluate alternative incentives that address these challenges of scalability, habit formation and crowd-out. The investigators will aim to encourage physical activity through alternative incentives - by making a meal donations on behalf of participants (prosocial incentives) and give participants monetary incentives (personal incentives). Both types of incentives have underpinnings in behavioral economics.

Meal donations harness prosocial preferences, which may be more powerful and less likely to reduce intrinsic motivation than equivalent monetary incentives.

The overall aim is to evaluate the impact of alternative incentives on step count of older adults in the short-term and long-term. Exploratory analysis will also evaluate the impact on physical and mental health. The investigators will recruit 200 older adults and randomize half of them to receive additional prosocial and personal incentives for their walking behavior. The other half will not receive these incentives. The investigators will track step count of these two groups for 8 weeks using a Fitbit device. Under the treatment functionality, participants accrue a meal donation and a point for Feeding America for each day that they meet the step goal.

The investigators plan to recruit older adults ages 55 and above at grocery stores and other locations around San Diego, CA. Recruitment will be on a rolling basis. PI Samek has recruited participants at grocery stores in prior studies, hence the investigators believe this is feasible. Participation will be limited to individuals who own a smart phone (61% of older adults in the US own a smart phone, and the investigators expect this number to grow as the population ages). Studies have shown that older adults are open to using app-based technologies, for example older adults are accepting of mindfulness apps.

The research team will be given access to participants' Fitbit data through Fitabase, a research platform that collects data from internet connected consumer activity devices. The investigators identified 7,500 steps as an appropriate goal as studies show older adults walk 4,000 steps on average. For the treatment group, meals will be donated by the research team to Feeding America for each day they meet the step goal of 7,500 steps. They will also receive money for each day they meet the step goal of 7,500 steps a day, for up to 5 days a week. The control group will not receive these incentives for their walking behavior, but their daily step count data will be collected.

Participants will receive a Fitbit upon enrollment. The investigators will collect their physical activity data for 1 week, as their baseline physical activity. After 1 week, individuals who on average less than 6000 per day, will be randomized to the treatment group, which receives the incentives for 4 weeks, or to a control group which does not.

The investigators will also collect follow up data for 1 weeks.

Individuals who on average walk more than 6000 steps per day during the 1 week baseline period will be dropped from the study.

Inclusion Criteria

• 55 years old or older
• own a smartphone
• can walk independently
• how often they walked outside their home or yard for fun or exercise in the past week - Never, Seldom (1-2 days), Sometimes (3-4 days), or Often (5-7 days)? They can participate if they respond never or seldom.

Exclusion Criteria

• below 55 years
• do not own a smartphone
• unable to walk independently
• how often they walked outside their home or yard for fun or exercise in the past week
• Never, Seldom (1-2 days), Sometimes (3-4 days), or Often (5-7 days)? They can not participate if they respond sometimes or often.