Inclusion Criteria:

• Participants must:
• * have a body mass index between 25-45 kg/m2
• * have had a knee replacement (including primary, staged or independent bilateral, or revision) \<6 months prior to baseline assessment
• * have a computer, tablet, or smartphone with active internet access to self-monitor online and/or have a device or computer compatible with Fitbit
• * completion of baseline assessment measures (height, weight, function tests, surveys, ≥4 days valid of activity monitoring, and 1 day of dietary recall)
• * be English-speaking and able to read consent and study materials written in English
• * be willing to attend 4 in-person assessments.

Exclusion Criteria:

• * have any contraindications to diet or weight loss
• * undergo simultaneous bilateral knee replacement or have a scheduled or anticipated knee replacement for the contralateral knee within the next 18 months
• * have a mobility limiting comorbidity unrelated to knee replacement (e.g. spinal stenosis, fibromyalgia, peripheral vascular disease, stroke)
• * are taking anti-obesity medications
• * are enrolled in a formal weight loss program
• * had or are planning to have bariatric/gastric/lap band surgery
• * are planning to relocate out of the Columbia or Greenville, SC areas in the next 18 months.