Table 3.

Nonparticipation questionnaire summary (n=69).

Questionnaire items		Value, n (%)
Age range (years)
	<20	13 (19)
	20-29	36 (52)
	30-39	11 (16)
	40-49	5 (7)
	50-59	2 (3)
	Prefer not to answer	2 (3)
Sex
	Female	51 (74)
	Male	18 (26)
	Other	0 (0)
Reasons did not take part
	Not available during the study session times	30 (43)
	Data privacy concerns around Amazon collecting information on my diet	9 (13)
	Data privacy concerns around researchers collecting information on my diet	3 (4)
	Concerns that Alexa will inadvertently listen to other conversations	9 (13)
	I do not eat or drink during my working hours	3 (4)
	Picking up and returning the device was inconvenient	5 (7)
	Other reasona	21 (30)
Has a voice-controlled device
	No	35 (51)
	Yes, but it is used by others, not me	10 (14)
	Yes, and I use it	24 (35)
Happy to use a voice-controlled system (eg, Alexa) at home for research in the future
	Yes	42 (61)
	No	13 (19)
	Not sure	14 (20)
Happy to use a voice-controlled system (eg, Alexa) on a wearable device such as a smart watch for research
	Yes	39 (57)
	No	18 (26)
	Not sure	12 (17)

^aParticipants who stated “other” were able to complete a free-text response; these are summarized in Section S4 in Multimedia Appendix 1. A summary of all items in the nonparticipation questionnaire is provided in Table S4 in Multimedia Appendix 1.