Promote Weight Loss in Obese Peripheral Artery Disease (PAD) Patients to Prevent Mobility Loss

Inclusion criteria are a) presence of PAD; b) BMI\> 25 kg/m2; c) Age \>= 18. The diagnosis of PAD will be based on the following. First, an ankle brachial index (ABI) value \<= 0.90, which is a well-accepted standard for diagnosing PAD. People with a toe brachial index of \<=0.70, performed at the study visit, will be eligible. Second, people with an ABI of \>0.90 and \<=1.00 who experience a 20% or greater drop in ABI in either leg after the heel-rise test will also be included. Third, potential participants with an ABI \> 0.90 who provide vascular laboratory evidence or angiographic evidence of PAD will be included. Prior vascular laboratory evidence consists of objective evidence of PAD including toe brachial index (TBI) \< 0.70, Duplex measure showing 70% stenosis or greater, a post-exercise ABI drop in either leg of 20% or greater, or ABI values \<= 0.90. Angiographic evidence of PAD consists of a stenosis of 70% or greater in a lower extremity artery. Fourth, people with a history of lower extremity revascularization who do not meet the criterion above and have an ABI \> 0.90 with a 20% or higher drop in ABI after an exercise test will be eligible if they have symptomatic PAD. Symptomatic PAD will be defined as leg symptoms associated with exertion that resolved within 10 minutes of rest. The presence of symptomatic PAD will be determined based on the claudication questionnaire, the six-minute walk, or principal investigator interview/discussion with the potential participant. The post-exercise ABI drop will be measured by obtaining an ABI, having the participant exercise, and then immediately repeating the ABI. The exercise may consist of either the six-minute walk test or the heel-rise test. The heel-rise test consists of 50 heel rises at a rate of one per second. From the beginning of the trial until early 2023, we used the BMI inclusion criterion of \> 28 kg/m2 because overweight and obesity are defined as a BMI of 25 to 29 kg/m2 and \> 30 kg/m2, respectively, and because in our PAD cohorts, those with BMI \> 28 kg/m2 have significantly greater functional impairment and faster functional decline than those with BMI of 20-28 kg/m2. In order to increase the rate of recruitment, on 1/19/2022, investigators reduced the BMI inclusion criterion to \> 25 kg/ m2. People with BMI above 25 are overweight or obese and therefore are expected to benefit from the healthy lifestyle intervention. Exclusion Criteria: 1. Above or below knee amputation, critical limb ischemia, or wheelchair confinement. 2. Walking is limited by a condition other than PAD. 3. Failure to complete the study run-in, defined as not entering at least 800 Kcal of consumed calories per day for at least five days during the 14-day run-in\*. 4. Major surgery, coronary or leg revascularization in the past 3 months or anticipated in the next year. 5. Experienced a heart attack or stroke in the past 3 months. 6. Major medical illness including lung disease requiring oxygen or life-threatening illness, Parkinson's disease, a life-threatening illness with life expectancy less than six months, or cancer requiring treatment in the previous two years. \[NOTE: potential participants may still qualify if they have had treatment for an early stage cancer in the past two years and the prognosis is excellent. 7. Mini-Mental Status Examination (MMSE) score \< 23, dementia and substance abuse. Potential participants with an MMSE score of less than 23 may be eligible if the principal investigator determines that their lower score is due to reasons other than poor cognition. Other potential reasons for lower scores include poor literacy or that English is not their first language. 8. History of being treated for new onset or an acute episode of schizophrenia or psychosis in the past 6 months. 9. Hospitalization for a psychiatric disorder in the past 6 months. 10. BMI \> 45 kg/m2 11. History of a significant eating disorder that has been active within the past 5 years or any weight loss treatment in the past 6 months. Weight loss treatment includes weight watchers, any history of weight loss surgery, and using weight loss medications now or in the past six months. 12. Weight gain or loss of more than 25 pounds in the past six months 13. Potential participants unwilling/unable to use a smart phone and unwilling to attend weekly study sessions. 14. Excessive alcohol use, defined as \>14 drinks/week in men and \> 10 alcoholic drinks/week in women. 15. Current ulcer on bottom of foot 16. Current participation in supervised treadmill exercise, participation in supervised treadmill exercise in the past three months, or planning to participate in supervised treadmill exercise in the next year 17. Increase in angina or angina at rest. Potential participants may become eligible following an abnormal baseline treadmill stress test if they have evidence of an absence of coronary ischemia based on testing with their own physician. 18. Non-English speaking 19. Visual impairment that limits walking ability 20. Currently walking regularly for exercise at a level comparable to the amount of exercise prescribed in the intervention 21. Participation in or completion of a clinical trial in the previous three months. \[NOTE: after completing a stem cell or gene therapy intervention, participants will become eligible after the final study follow-up visit of the stem cell or gene therapy study so long as at least six months have passed since the final intervention administration. After completing a supplement or drug therapy (other than stem cell or gene therapy), participants will be eligible after the final study follow-up visit as long as at least three months have passed since the final intervention of the trial.\] 22. In addition to the above criteria, investigator discretion will be used to determine if the trial is unsafe or not a good fit for the potential participant * The run-in will also be used to assist participants with learning the app. However, they must demonstrate ability to enter at least 800 Kcal per day for at least five days of the run-in.