Table 1 Definitions of “perceptions on diet and fluid recommendations” variables

Perception [31] on whether renal diet is important

Data collected on a 5-point Likert scale of “1 = highly important; 2 = very important; 3 = moderately important; 4 = a little important; and 5 = not important” and a binary variable computed as “1 and 2 = 1” coded as “it is important” and “3–5 = 0” coded as “not so important”

Motivation [31] for following recommended diet

Data collected on a 7-point Likert scale of “1 = because I fully understand that my kidney condition requires to watch my diet; 2 = because watching my diet is important for my health; 3 = because a medical professional (doctor, nurse, or dietician) told me to do so; 4 = because I got sick after eating certain food that I was not supposed to eat; 5 = because I was hospitalized after eating certain food that I was not supposed to; 6 = I do not think watching my diet is important to me; 7 = other (specify): __.” A binary variable computed as “1 and 2 = 1” coded as “perceived health benefits (important for health and kidneys)” and “3–7 = 0” coded as “other reasons (counseling, hospitalization)”

Perception [31] on whether limiting fluid intake is important

Data collected on a 5-point Likert scale of “1 = highly important, 2 = very important, 3 = moderately important, 4 = a little important, and 5 = not important” and a binary variable computed as “1 and 2 = 1” coded as “it is important” and “3–5 = 0” coded as “not so important”

Motivation for limiting fluid intake

Data collected on a 7-point Likert scale of “1 = because I fully understand that my kidney condition requires to watch my diet; 2 = because watching my diet is important for my health; 3 = because a medical professional (doctor, nurse, or dietician) told me to do so; 4 = because I got sick after eating certain food that I was not supposed to eat; 5 = because I was hospitalized after eating certain food that I was not supposed to; 6 = I do not think watching my diet is important to me; 7 = other (specify): __.” A binary variable computed as “1 and 2 = 1” coded as “perceived health benefits (important for health and kidneys)” and “3–7 = 0” coded as “other reasons (counseling hospitalization)”

Perception to weight measurement

Data was collected on a 5-point Likert scale of “1 = highly important, 2 = very important, 3 = moderately important, 4 = a little important, and 5 = not important” and a Binary variable computed as “1 and 2 = 1” coded as “it is important” and “3–5 = 0” coded as “not so important”

Difficulty in watching diet intake

This was assessed as either “presence” and coded as “1” or “absence” and coded as “0” of difficulties in following diet recommendations.

Diet fits with other ways of eating [31, 33]

This was defined as the “flexibility of the diet to fit in with usual dietary habits” of the participants. This variable was assessed on a 9-point Likert scale of 1 = it fits in with my usual way of eating, 2 = it seems to contradict what I thought was healthy, 3 = it is difficult to combine with the rest of the family, 4 = it makes it difficult to eat out, 5 = it combines easily with other dietary advice I have been given, 6 = it is more expensive than my usual way of eating, 7 = I seem to have to eat more than I want, 8 = there are lots of foods I can no longer eat, 9 = I do not need to make any changes.” A Binary variable was computed as “1, 5, and 9 = 1,” coded as “yes diet is flexible” and “2, 3, 4, 6, 7, and 8 = 0,” coded as “diet is not flexible” and does not fit in with other eating habits.