Understanding the Impact of a Weight Loss Program: the roles of reach, retention, and effectiveness

Abstract

The objective of this paper is to demonstrate potential problems of relying on intention to treat analyses when initial reach is not accounted for. Archival data from seven worksites (n=10,513 employees) that completed a weight loss program was used to determine (a) the effectiveness of the program at the end of three and six months of participation, (b) the reach of the program into the eligible employee population, and (c) the proportion of the targeted employee population that ultimately benefited from the program and the degree to which they benefited (i.e., effectiveness that accounts for reach and retention). Intention to treat analyses using baseline value carried forward for participants lost to attrition revealed that participants lost a significant (p<.01), yet modest, 2.1 lbs of weight at 3 and 2.4 lbs of weight at 6 months of participation. Follow-up analyses were conducted to determine the overall proportion of the workforce that benefited (i.e., lost weight) at 6 months. Of the 1607 participants who were retained at 6 months, 1088 were successful in losing weight and lost, on average 9.4 pounds (95% CI: 8.8 to 9.9 pounds), a clinically significant 4.4% of initial body weight. Thus, 10.1% of the total employee population benefited from the weight loss program and lost a clinically relevant amount of weight. The findings of this study indicate that presenting reach by effectiveness data to the employers could help them in making more sophisticated decisions while choosing a commercial weight loss program for their employees when compared to traditional intention to treat analyses.