The goals for participants randomized to lifestyle were to achieve and maintain a weight reduction of at least 7% of initial body weight through diet and physical activity of moderate intensity, such as brisk
walking, for at least 150-min per week. A 16-session core curriculum (given approximately weekly in individual participant sessions) and subsequent individual sessions (usuallymonthly) and group sessions with case managers were designed to reinforce the behavioral changes. The medication interventions (metformin and placebo) were initiated at a dose of 850 mg taken orally once a day. At 1 month, the dose was increased to 850-mgtwice daily.Adherence was reinforced during individual quarterly visits with casemanagers. Standard lifestyle
recommendations were provided to all groups through written information and an annual 20- to 30-min individual session that emphasized the importance of a healthy lifestyle. Mean follow-up at the end of the DPP was 3.2 years. For the purposes of this analysis, we assumed that all subjects were enrolled in the DPP for exactly 3 years.
DPP/DPPOS bridge. At the end of the DPP in July 2001, masked treatment was discontinued and each participant had a 1-h debriefing and closure visit during which he or she was informed of the main DPP results. In light of the proven benefits of lifestyle, all participants were offered a group-implemented 16-session lifestyle intervention between January and July 2002. Forty percent of lifestyle, fifty-eight percent
of metformin, and fifty-seven percent of placebo participants attended at least one session (11). Each session lasted 1 h and was taught by one staff member. Participants received reminders for the sessions and the full packet of course materials. The original lifestyle group was offered additional lifestyle
support and was not encouraged to take metformin.
The original metformin group was encouraged to continue metformin and to participate in the group lifestyle intervention. Those randomized to placebo stopped placebo and were encouraged to participate
in the group lifestyle intervention. For the purposes of this analysis, we assumed that year 4 represented the DPP/DPPOS bridge.
DPPOS maintenance. The DPPOS maintenance phase started in September 2002. All active participants were eligible for continued follow-up, and 2,766 of 3,150 (88%) enrolled (4). These included 910 from lifestyle, 924 from metformin, and 932 from placebo. During the DPPOS, the group lifestyle intervention was implemented as the Healthy Lifestyle Program (HELP) for all participants. HELP reinforced the original weight loss and physical activity goals and focused on current topics in nutrition, physical activity, stress management, and diabetes prevention. HELP consisted of four quarterly 1-h group visits. All participants received a reminder for HELP sessions. Although all participants were invited to attend all HELP sessions, many chose to attend fewer.