Objective: To examine changes in eating behaviors and physical activity, as well as predictors of weight loss success, in obese adults who participated in a 2-year behavioral weight loss intervention conducted in a primary care setting.
Design: A longitudinal, randomized controlled, multisite trial.
Subjects: Three hundred ninety obese (body mass index, 30-50 kg m(-2)) adults, ≥ 21 years, in the Philadelphia region.
Methods: Participants were assigned to one of three interventions: (1) Usual Care (quarterly primary care provider (PCP) visits that included education on diet and exercise); (2) Brief Lifestyle Counseling (quarterly PCP visits plus monthly lifestyle counseling (LC) sessions about behavioral weight control); or (3) Enhanced Brief LC (the previous intervention with a choice of meal replacements or weight loss medication).
Results: At month 24, participants in both Brief LC and Enhanced Brief LC reported significantly greater improvements in mean (± s.e.) dietary restraint than those in Usual Care (4.4 ± 0.5, 4.8 ± 0.5 and 2.8 ± 0.5, respectively; both P-values ≤ 0.016). The percentage of calories from fat, along with fruit and vegetable consumption, did not differ significantly among the three groups. At month 24, both the Brief LC and Enhanced Brief LC groups reported significantly greater increases than usual care in energy expenditure (kcal per week) from moderately vigorous activity (+593.4 ± 175.9, +415.4 ± 179.6 and -70.4 ± 185.5 kcal per week, respectively; both P-values ≤ 0.037). The strongest predictor of weight loss at month 6 (partial R(2)=33.4%, P<0.0001) and at month 24 (partial R(2)=19.3%, P<0.001) was food records completed during the first 6 months. Participants who achieved a 5% weight loss at month 6 had 4.7 times greater odds of maintaining a ≥ 5% weight loss at month 24.
Conclusions: A behavioral weight loss intervention delivered in a primary care setting can result in significant weight loss, with corresponding improvements in eating restraint and energy expenditure. Moreover, completion of food records, along with weight loss at month 6, is a strong predictor of long-term weight loss.