Brief Summary: Alcohol use disorder (AUD) is a significant and costly public health problem that affects one-third of the U.S. population in their lifetime. Specifically, unhealthy alcohol use is common among persons living with HIV (PLWH) and increases the risk of developing negative outcomes. Antiretroviral therapy (ART) has shown increasing life expectancy and decreased HIV-related deaths, leading to a growing older adult HIV population. Yet, HIV accelerates the aging process and increases the risk for numerous chronic health conditions that compromise physical and mental health functioning and quality of life. Thus, PLWH continue to have shorter life expectancies relative to the general population and these multimorbidities explain this increased risk. In this context, unhealthy alcohol use among PLWH can further increase the risk for negative outcomes.

Physical activity (PA) interventions can be used as an effective way to address unhealthy alcohol use among PLWH. Previous PA interventions have shown low generalizability and high loss to follow-up. Therefore, an intervention that is home-based, including lifestyle physical activity (LPA) with mobile health-delivered components is designed following the physical activity (PA) paradigm.

Participants in this randomized controlled trial will be assigned to one of two study arms -- either the LPA or Fitbit Only intervention - both lasting 12-weeks. Both study arms will utilize a Fitbit to track daily step counts.

In addition to utilizing a Fitbit, the LPA arm will receive 7 LPA sessions with a trained interventionist to assist in adding LPA to the participant's routine.

The Fitbit only arm will receive only brief check-in phone calls and only related to assisting with any Fitbit functioning issues.

Follow-up assessments will take place at 3 and 6 months.

Primary Aims - Physical Activity and Drinking Outcomes

To test the efficacy of a 12-week LPA intervention among low-active, PLWH engaged in unhealthy drinking. Participants will be randomly assigned to either: (a) LPA or (b) Fitbit Only control condition. Relative to Fitbit Only, the investigators hypothesize that:

1. LPA will demonstrate decreases in unhealthy drinking (i.e., drinks/week) end-of-treatment (EOT) and 3 months later (i.e., 6-month follow-up).
2. LPA will demonstrate higher objective-determined physical activity engagement (i.e., steps/day) at the EOT and at the 6-month follow-up.

Secondary Aims - Physical and Mental Health Functioning Outcomes Relative to Fitbit Only or LPA will result in decreased negative affect and sedentary behavior (i.e., minutes spent sitting/day), heavy drinking days, alcohol-related problems, and increases in adaptive coping, PA self-efficacy, PA motivation, and physical/mental functioning at EOT and 6-month follow-ups.

Tertiary Aims - Examining Mechanisms

1. Decreases in negative affect and increases in adaptive coping during the intervention period will mediate the relationship between LPA and drinking outcomes at the 6-month follow-up
2. Increases in PA self-efficacy and motivation will mediate the effect of LPA on PA engagement
3. Utilizing Ecological momentary assessment (EMA) and Fitbit data, we hypothesize higher negative affect and urges to drink earlier in the day is more likely to increase the likelihood of engaging in bouts of PA later in the day at EOT, relative to baseline, and among persons randomized to LPA versus Fitbit Only.

Inclusion Criteria:

• Have the ability to confirm HIV diagnosis either through visual evidence of ART medication or medical record
• Engaged in unhealthy drinking, defined as: >7 drinks for women / > 14 drinks for men per week OR ≥ 3 drinks for women / ≥4 drinks for men on one occasion in the past month.
• Have a smartphone
• Considered low active: 150 minutes or less of average weekly physical activity
• Lives in the USA
• Has a U.S. mailing address

Exclusion Criteria:

• History of bipolar, schizophrenia, schizoaffective disorder or mania per self report.
• History of withdrawal-related seizures or delirium tremens per self report.
• Current non-pharmacological treatment for alcohol use disorder.
• Unable to provide one or more individuals for follow up contact.
• Current DSM-5 diagnosis of anorexia or bulimia nervosa per self report.
• Marked organic impairment according to responses to the diagnostic assessments
• Physical or medical problems that would not allow safe participation in a program of moderate intensity PA
• Individual who is unwilling to provide their sex at birth
• Limited or non-readers