Effect of dose of behavioral weight loss treatment on glycemic control in adults with prediabetes

OBJECTIVE: This study examined the effects of three doses of behavioral weight loss treatment, compared with a nutrition education control group, on changes in glycemic control in individuals with obesity and prediabetes. RESEARCH DESIGN AND METHODS: The study included 287 adults (77% female, 81% White; mean (SD) age=54.1 (10.5) years, body mass index=36.3 (3.9) kg/m(2), and hemoglobin A1c (HbA1c)=5.9 (0.2%)). Participants were randomized to one of three behavioral treatment doses (high=24 sessions, moderate=16 sessions, or low=8 sessions) or to an education group (control=8 sessions). Changes in HbA1c, fasting glucose, and body weight were assessed from baseline to 6 months. RESULTS: Mean (99.2% credible interval (CI)) reductions in HbA1c were 0.11% (0.07% to 0.16%), 0.08% (0.03% to 0.13%), 0.03% (–0.01% to 0.07%), and 0.02% (–0.02% to 0.07%), for the high, moderate, low, and control conditions, respectively. Mean (CI) reductions in fasting blood glucose were 0.26 mmol/L (0.14 to 0.39), 0.09 mmol/L (0 to 0.19), 0.01 mmol/L (–0.07 to 0.09), and 0.04 mmol/L (–0.03 to 0.12) for the high, moderate, low, and control conditions, respectively. The high-dose treatment produced significantly greater reductions in HbA1c and fasting blood glucose than the low-dose and control conditions (posterior probabilities (pp)<0.001); no other significant between-group differences were observed. Mean (CI) reductions in body weight were 10.91 kg (9.30 to 12.64), 10.08 kg (8.38 to 11.72), 6.35 kg (5.19 to 7.69), and 3.82 kg (3.04 to 4.54) for the high, moderate, low, and control conditions, respectively. All between-group differences in 6-month weight change were significant (pps<0.001) except for the high-dose versus moderate-dose comparison. CONCLUSION: For adults with obesity and prediabetes a high dose of behavioral treatment involving 24 sessions over 6 months may be needed to optimize improvements in glycemic control. TRIAL REGISTRATION NUMBER: NCT00912652.