Bariatric surgery is the most effective intervention for morbid obesity, however, up to 30% of post-bariatric surgery patients have suboptimal weight loss outcomes. The aim of this dissertation was to investigate the impact of controllable environmental factors (i.e., typical plate size) on weight loss success in a post-bariatric sample.

In a large (n= 487) online survey of patients at least 1 year after surgery, participants answered questions which assessed controllable environmental factors including the location of meals at home, the frequency of dining out, the size of dishware and serving utensils, and the visibility, accessibility, and packaging for different types of snacks. Based on these questions, we developed a weight loss likelihood success (WLLS) scale, which was a numerical score representing total risk-decreasing factors minus risk-increasing factors and we examined this score's relationship with weight loss success.

The results suggest that those who had suboptimal weight outcomes reported significantly higher tendencies to have previously identified risk-increasing factors than those who had successful weight outcomes. These risk-increasing factors included having sweet and salty snacks visible on the counter (X 2=5.16(1), p=0.016), eating off dinner-size versus salad-size plates (X2=4.1(1), p=0.028), eating snack foods from large packages (X2=9.6(1), p=0.001), eating potato chips/salty snacks more frequently (t(485)=3.2, p=.002), eating meals in rooms besides the kitchen and dining room more frequently ( t(485)=-4.06, p < 0.001), and dining out more frequently (t(215)=2.7, p=0.007). Subjects with suboptimal weight loss outcomes also reported significantly less risk-decreasing factors than those who had successful weight outcomes. These included having visible fresh fruit on the counter ( X2=11.1(1), p=0.001), leaving food on one's plate more frequently t(485)=-2.5, p=0.013), and eating fruit as an afternoon snack more frequently (t(279)=-3.27, p=0.001). When examining total risk-increasing and risk-decreasing factors and the WLLS, those who experienced successful weight loss had significantly less risk-increasing factors (t(480)= 5.41, p < .001), significantly more risk-decreasing factors t(485)=-5.44, p < .001), and significantly higher WLLS scores (r=.26, n=482, p<.001). The environmental factors examined here are controllable by bariatric patients and many appear to affect post-bariatric patient's success with weight loss.