Among women randomized to an Atkins weight-loss diet, positive 6-month outcome realizations regarding perceived improvements in physical shape and appearance predicted less weight regain during a 6–12 month follow-up, after controlling for baseline outcome expectations and the interaction between expectations and realizations. The result mirrors research highlighting the importance of realizations for long-term health behavior change success (Brassington, et al., 2002
; Finch, et al., 2005
; Neff & King, 1995
; Wilcox, et al., 2006
Neither baseline expectations nor the interaction (i.e., discrepancy) between expectations and realizations predicted regain in the Atkins group. The former is consistent with previous research (Ames, et al., 2005
). The interaction’s failure to predict regain runs counter to theories suggesting that discrepancies between inflated expectations and subsequent dissatisfaction lead to poor long-term outcomes (Polivy & Herman, 2002
; Rothman, 2000
), although the finding is consistent with one study in which discrepancies did not predict long-term exercise adherence (Sears & Stanton, 2001
). Atkins participants reported improvements in shape and appearance that were close to their expectations, particularly relative to other diet groups; it is possible that this narrower range of expectation-realization discrepancies impacted the results. Alternatively, current theories—though intuitively appealing—may overemphasize outcome expectations and discrepancies in shaping behavior.
A descriptive analysis revealed three distinct patterns of 6–12 month regain based on Atkins participants’ initial weight losses from baseline to 6 months and 6-month outcome realizations. First, those who initially lost larger amounts of weight and reported positive realizations regained very little from 6–12 months, an ideal combination. Second, regardless of realizations, participants who initially lost smaller amounts of weight tended to gain weight from 6–12 months. Initial lack of weight loss appeared to increase the risk for subsequent gain, consistent with recent findings that a “slow start” to weight loss is associated with worse long-term maintenance (Nackers, Ross, & Perri, 2010
). Third, the extremely few participants who initially lost larger amounts of weight and yet reported negative realizations regained considerable weight. Though small, this may represent another group at high risk.
Limitations to this study include its applicability only to the generally successful Atkins diet group (Gardner, et al., 2007
). Smaller weight loss ranges may have restricted the detection of patterns in the remaining groups. Generalizability also is limited by the predominantly middle-aged, well-educated female sample, and replication in larger samples is indicated. Lastly, restricted sample sizes precluded examination of whether outcome expectation domains of greatest perceived importance differed by ethnicity, leaving room for future research.
This study’s strengths include its prospective design, evaluation of a popular “real-world” diet, focus on the domain of physical shape and appearance judged important by participants, and pre-planned, novel test of outcome expectations, realizations, and their interaction when predicting weight regain. Future research should determine the mechanisms through which realizations impact regain. For example, it is possible that positive realizations lead to long-term weight loss by fostering adherence to weight control behaviors, including dietary, physical activity, and self-monitoring behaviors which may contribute to success (Wing & Phelan, 2005
). (Of note, greater adherence to prescribed dietary restrictions was associated with greater 12-month weight loss in this trial (Alhassan, Kim, Bersamin, King, & Gardner, 2008
).) Conversely, negative realizations—even when initial weight loss is objectively “successful”—may lead to regain through abandonment of weight control behaviors. While acknowledging the difficulty of altering realizations (Jeffery, Linde, Finch, Rothman, & King, 2006
), experimental research is needed to determine whether improving the perceived benefits of weight loss could improve adherence, and subsequently, long-term weight outcomes. Our descriptive results also suggest that inadequate initial weight loss is a potential predictor of regain. Additional prospective research to identify subgroups at high risk for regain offers opportunities to better tailor interventions and improve long-term success.