2.1.2. Study Procedures
eating behavior, hunger and fullness
BLIND
In this randomized crossover study, the familiarization trial and main experimental trials were conducted from January to March 2023. There were three trials: a familiarization trial and two main experimental trials. Each experimental trial, including the familiarization trial, was conducted at least 7 days apart. All trials were conducted at lunchtime (12.00–13.00 h), with the time standardized for each participant.In the familiarization trial, participants ate a lunch test meal of ramen noodles with chopsticks and a regular spoon to familiarize themselves with the laboratory environment. In the subsequent two main experimental trials, the participants ate for lunch ramen with chopsticks and a regular spoon (hereinafter referred to as the regular spoon condition) and with chopsticks and a perforated spoon (hereinafter referred to as the perforated spoon condition) in random order. Participants were randomly allocated to two groups using a random number generator to adjust for order effects. To blind participants to the true aim of the study, we conducted the experiment without informing them of the purpose of the study because informing them of the purpose and content before the start of the experiment may change their eating behavior. The authors who conducted the experiments and measured the results were not blinded.Participants, including those in the familiarization trial, were asked to refrain from moderate or strenuous exercise and to not consume alcohol from the day before the study until the time of the study, and to spend time as usual. On the day of the main experimental trials, the participants were instructed to replicate the breakfast and morning activity patterns on the day of the familiarization trial. Some participants habitually ate breakfast every day, while others did not. Therefore, participants were instructed that their morning routine should be the same as that on the familiarization trial day, including eating breakfast. Those who ate breakfast on the day of the familiarization trial were instructed to eat breakfast before the two main tests. Participants were instructed to eat breakfast as usual, without any instructions on what to eat. Those not accustomed to eating breakfast were asked to participate in the study without eating breakfast.The familiarization and main experimental trials were conducted in a room with a separate eating area where the participants could not see what others were eating. Before being offered the test meal and drinking water, participants responded to questions about their appetite (hunger and fullness) and how they spent the morning (e.g., breakfast intake, snacking, and physical activity). Participants were given standardized instructions to “eat ramen as usual.” No instructions were given on how to use the spoon. After the meal, participants were asked about their subjective appetites. They were instructed to remain in the study room until they responded to the questions regarding their subjective appetite after meals.