All adolescents, except one youth who participated but refused to give up their phone, were willing to complete the Buffet Challenge at all time points (defined as remaining in the buffet room for 30 min without their cell phone). Other challenges during administration (104 total buffets) included unavailability of specific foods (occurrences = 13), weighing error (occurrence = 2), item taken/unable to be weighed (occurrence = 2), recording error (occurrence = 1), adolescent ate prior (occurrence = 1), vegetarian food ordered in error (occurrence = 1), and standard buffet ordered instead of vegetarian (occurrence = 1). Twelve adolescents did not consume anything during the buffet (n = 6 at T1, n = 5 at T2, and n = 1 at T3); all were supplemented by parents following the task. One adolescent exhibited significant distress following the Buffet Challenge at baseline but willingly engaged in the Buffet Challenge at both future timepoints. One adolescent scraped the inside of their wrist with a plastic knife during the task (the knife was removed). An on-site psychologist met with both adolescents. The first was able to engage in coping behavior and had reduced distress. The second reported that they were attempting to “get out” of treatment and subsequently agreed to continue the assessment.

At mid-treatment, participants completing the Buffet Challenge were in Phase I (48%) or II (45%) of FBT, with 7% in Phase III. By EOT, most participants were in Phase II (57%) of FBT, with 14% in Phase I, and 29% in Phase III. Table 2 presents macronutrient and liquid consumption, with frequency and duration of eating-related behaviors shown in Table 3. The most common ED behaviors across all timepoints were staring at food, fidgeting, and inappropriate napkin use.

Associations among buffet related consumption and parent-reported ED behavior differed across maternal and paternal report (Table 5). Higher maternal ABOS scores at baseline were associated with lower caloric density consumed during the Buffet Challenge. Surprisingly, higher maternal ABOS scores at EOT were associated with a significantly greater portion fats at the EOT Buffet Challenge. We did not observe significant associations between paternal ABOS scores and buffet data at any timepoint.

Results assessing buffet variables across remission status (i.e., not remitted, partially remitted, and fully remitted) are shown in Table 4. Mid-treatment Buffet Challenge data were collected for 31 adolescents (Nfull remission = 15, Npartial remission = 13, Nnot remitted = 3). Kruskall-Wallis tests yielded a moderate, non-significant effect across groups in caloric density consumed (see Table 4), where caloric density was lowest in the not remitted group (m = 0.9, sd = 0.3), compared to those partially (m = 1.1, sd = 0.9) or fully remitted (m = 1.6, sd = 0.7) (Table 5).

For the EOT Buffet Challenge (N = 21), 13 adolescents met criteria for full remission, 6 for partial remission, and 2 were not remitted. Kruskal–Wallis tests revealed a large, non-significant effect across remission groups for caloric density (see Table 4), which was lowest in the not remitted group (m = 0.9, sd = 0.2), compared to those partially (m = 1.3, sd = 1.0), or fully remitted (m = 1.6, sd = 0.4). There was a medium, non-significant effect for non-caloric liquid consumption, which was highest in the not remitted group (m = 17.0, sd = 0.0), compared to those partially (m = 6.0, sd = 7.1), or fully remitted (m = 6.6, sd = 6.1).

Results assessing buffet variables across FBT phase (Phase I, II, and II) are shown in Table 4. At mid-treatment, we found a large, non-significant effect across FBT phase in caloric density (Table 4). Participants in Phase I consumed the lowest caloric density (m = 1.1, sd = 0.7), compared with those in Phase II and III, respectively (m = 1.5, sd = 0.8; m = 2.4, sd = 0.4). Medium, non-significant effects were observed for percent of daily intake consumed, fat intake, and carbohydrate intake. Individuals in Phase I consumed approximately 8.1% (sd = 7.5) of their daily intake, compared with 11.4% (sd = 7.6) and 22.0% (sd = 2.5) in Phase II and III, respectively. Those in Phase I had the lowest intake from fats (m = 22.1%, sd = 15.3), compared with 30.6% (sd = 17.3) and 41.1% (sd = 5.3) in Phase II and III respectively. Percent intake from carbohydrates was lowest for those in Phase I of FBT (m = 37.9%, sd = 26.2), compared with 39.2% (sd = 22.8) and 45.1% (sd = 5.4) in Phase II and III, respectively.

At EOT, medium, non-significant effects across Phase for percentage of intake from fats (see Table 4) were observed. Fat intake was lower for those in Phase I (m = 31.5%, sd = 16.0) and Phase II (m = 31.2%, sd = 14.4), compared to those in Phase III (m = 36.6%, sd = 12.1). For percent intake from carbohydrates, intake was highest for those in Phase I (m = 49.1%, sd = 18.6) compared to those in Phase II (m = 40.2%, sd = 16.7) and Phase III (m = 48.7%, sd = 10.2). For non-caloric liquid consumption, those in Phase I consumed an average of 8.3 floz (sd = 8.5), compared with 7.1 (sd = 6.9) and 7.6 (sd = 6.7) in Phase II and III, respectively.

We observed only small (caloric density and non-caloric liquid intake) and negligible non-significant effects at baseline across all variables for those who did and did not achieve early weight gain (i.e., 4lbs in the first four weeks).

We compared EOT buffet data of participants who went on to a higher level of care (N = 5) post-treatment compared to those who did not (N = 13). We observed medium, non-significant effect sizes between groups for percentage of intake from fats (Table 4), where those who were referred to a higher level of care consumed on average of 22.8% (sd = 16.1) of their meal from fats compared to an average of 33.2% for those who were not (sd = 11.0). For percentage of intake from protein, those referred to a higher level of care consumed on average of 13.3% (sd = 12.8) of their meal from proteins compared to an average of 21.6% for those who were not (sd = 9.2).