Group Size Is Not a Determinant of Weight Loss Goal

CHICAGO—Group size is not independently associated with the achievement of 5% weight loss or the 7% weight loss goal in high-risk adults participating in a diabetes prevention program, researchers reported at the 73rd Scientific Sessions of the American Diabetes Association.

“Intensive lifestyle intervention weight loss goals can be achieved as effectively with large groups as small groups in adults at high risk for cardiovascular disease and type 2 diabetes,” said Sarah Brokaw, MPH, program manager at the Division of Chronic Disease Prevention and Control at the Montana Department of Public Health and Human Services in Helena.

Her team conducted a study to assess if group size is associated with weight loss goal among 841 individuals who participated in an adapted Diabetes Prevention Program (DPP).  The smaller groups had fewer than 16 participants, whereas the larger groups had 16 or more participants.

The National Institutes of Health (NIH) and Finnish DPP studies demonstrated that the incidence of type 2 diabetes in high-risk adults can be significantly decreased through lifestyle modification, Brokaw pointed out. While the landmark clinical trials delivered the DPP intervention to participants in a one-on-one format, translation studies have shown that the intervention can be effectively delivered in a group setting with similar weight loss outcomes at significantly lower cost per participant.

Several prior studies that have translated the DPP have reported a range in group size. One such study reported a mean of four participants, while others have reported as many as 34 participants.

Until the present study, investigators had not examined the optimal group size to deliver DPP or even if group size affects achievement of weight loss targets.

 The Montana study included adults 841 patients aged 18 and older with a body mass index (BMI) of 25 kg/m2 or greater and one or more of the following risk factors for cardiovascular disease and type 2 diabetes: a diagnosis of prediabetes, impaired glucose tolerance, or impaired fasting glucose; hemoglobin A1C of 5.7% to 6.4%; high blood pressure; dyslipidemia (triglycerides above 150 mg/dL, low-density lipoprotein cholesterol below 40 mg/dL for men and below 50 mg/dL for women); and a history of gestational diabetes or had given birth to a baby weighing more than nine pounds.

The median group size was 16 participants. The mean age of participants was 53.4 years, and 82% of them were female. The mean number of core sessions attended was 13, and 36% of participants achieved the 7% weight loss goal.

Overall, the study found no significant differences in mean weight loss among participants in the smaller groups (5.1 kg) compared with the larger groups (5.8 kg). A similar proportion of participants in the smaller and larger groups achieved the 7% weight loss goal (33% and 39%, respectively).

Analyses adjusting for age, sex, baseline BMI, achievement of the physical activity goal, number of weeks self-monitoring fat intake, and group size showed that only two factors were independently associated with achievement of the weight loss goal: frequency of self-monitoring of fat intake and achievement of the physical activity goal. Group size was not independently associated with achievement of the 7% weight loss goal.

Brokaw cautioned that the analysis did not adjust for demographic characteristics such as household income or psychosocial characteristics such as depression. The DPP, however, found that these variables were not independently associated with weight loss outcomes.

In addition, self-monitored dietary fat and physical activity were used, which introduces the potential for self-report bias and recall bias.

“The overall findings from this translation study indicate that weight loss outcomes similar to the NIH DPP can be achieved in practice and that group size is not associated with participant weight loss outcomes,” Brokaw said.

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