Similarly, to two previous studies, most individuals in the current sample remained within 1.15% of their weight from SV to BV [1,2]. However, a much smaller percentage of participants gained weight pretreatment compared to all previous findings (16% versus 23%, 29.7%, and 48.9%) [1,2,3]. Importantly, only West and colleagues (2011), like the current protocol, required dietary and exercise self-monitoring before BV. Participants in West and colleagues (2011) experienced weight gain at a more similar rate (23%) [2] as this study (16%), suggesting that self-monitoring between SV and BV, perhaps, protected some individuals from experiencing significant weight gain.
The current study had fewer days, on average, during the pretreatment period compared to the previous studies (M = 14.6 versus 39.4, 42.7, and 50) [1,2,3]. Because there was a shorter window between SV to BV due to individual randomization, perhaps, fewer participants had the opportunity to gain weight. And, not surprisingly, fewer days between SV and BV was associated with weight stability. However, only one previous study found a similar association between weight change and pretreatment length of time [3]. Yet, despite the short time window in the current study, almost half (40.5%) of individuals still experienced significant weight fluctuations. Current results are an extension of previous findings [1,2,3], suggesting that some participants start to make significant behavioral changes during pretreatment period of weight loss interventions and other participants may use the time between SV and BV to indulge in foods that they believe will be restricted once they begin the intervention. Thus, recommending that participants continue to engage in self-regulation behaviors (e.g., self-monitoring, self-weighing) beyond the potential behavioral run-in might provide support to those more vulnerable to early weight gains.
For example, individuals identified or classified as African American and Other race were more likely to gain weight during the pretreatment period compared to those identified as Caucasian, in this racially and ethnically diverse sample (i.e., 20% African American, 15% Other races; 23% Hispanic/Latino). This racial difference was contrary to all previous findings suggesting no demographic differences in pretreatment changes [1,2,3], even in the previous sample that was predominately Black [3]. Although there were no racial differences in the impact of these gains on eventual treatment outcome, future weight loss interventions might need to account for both SV and BV starting weights when examining racial differences in treatment efficacy, particularly if these findings are replicated in future research.
Consistent with two previous studies [1,3], pretreatment weight change was related to treatment outcomes when weight loss success was measured starting with the screening visit. In the current study, those who lost pretreatment weight were more likely to lose weight from SV to 4-months. However, the current study observed outcomes over a longer time compared to previous studies [1-3] and found that pretreatment weight change was not independently related to outcomes at 12-months when starting from either SV or BV weights. These findings indicate that pretreatment weight changes may be more influential to success earlier in treatment, especially when the pretreatment period is included when measuring treatment outcomes.
However, in the current study, sociodemographic differences influenced the relationship between the pretreatment period and outcomes. Among individuals who gained weight pretreatment, younger adults were more vulnerable to less weight loss compared to older individuals. Importantly, younger personnel in the current sample were also less likely to be retained for data collection, as well as experienced less weight loss overall [6]. It may be that weight gain before an intervention is more predictive of poor outcomes for younger participants. Perhaps, young adults are more likely to feel discouraged after experiencing pretreatment gains and could benefit from intervention support during this period [1]. Notably, these age group differences might be unique given that this sample was slightly younger than previous samples [1,2,3], since unfortunately, behavioral weight loss trials often underrepresent individuals between 18-35 years of age [8,9].
Surprisingly, pretreatment weight change was not related to most weight loss behaviors within the intervention (i.e., self-weighing, dietary, or exercise self-monitoring frequency), dissimilarly from past findings [2]. However, pretreatment weight loss was associated with replacing a higher frequency of meals and snacks with low calorie and fat alternatives. Findings indicate that perhaps, pretreatment behaviors are not predictive of engagement with all intervention protocol.
The potential limits to generalizability in the current sample of active duty military personnel should be acknowledged. This sample has access to additional weight loss resources (e.g., free fitness centers, healthcare) as well as participates in annually required fitness tests. Although the prevalence of overweight and obesity in the U.S. military is high (60.8%) [10], the current sample had lower starting weights compared to previous studies [6]. Yet, enrollment in this setting facilitated the inclusion of a younger and more racially, ethnically, and gender diverse sample compared to previous weight loss research [8,9,11]. Finally, although there was no difference in pretreatment weight change and later randomization to either the CI or SP condition, distribution of pretreatment weight change categories might not have been perfectly randomized across the two treatment conditions [3].