Table 5.

Key barriers, themes and quotes (n 25)

COM-B	TDF	Sub-theme	Quote
Physical opportunity	Environmental context	1.Time 2.Food environment at work/canteen 3.Budget 4.Treats in for kids.	“For me it is time, by the time you get home from work, and maybe have done overtime, you couldn’t be bothered” (male 40, further education, FG1: P1) “There is nothing healthy in a canteen” (male 50, higher education, FG2: P10) “I am on my own here with 4 kids, so budget is definitely a factor.” (female 40, low education, I: P18) “There are always buns, biscuits in the cupboards, for visitors and kids.” (female 48, further education, I: P20)
Reflective motivation	Belief about capabilities	1.Convenience 2.Taste preference 3.Mindset	“Kids don’t want healthy stuff, so sometimes I have convenience stuff to make it easier for me” (female 40, low education, I: P17) “I think if I was going to change my diet, I would have to be in the right frame of mind” (male 51, low education, I: P13) “There is stuff there I won’t eat and that is that” (male 51, further education, FG2:P7)
Psychological capability	Knowledge	1.Lack knowledge of MIND diet and foods	“If you don’t know what is healthy for your brain, you won’t eat that way” (male 40, further education, FG1: P2) “Well probably mainly cos I didn’t know it would have any benefit on my brain”. (Female 45, low education, I: P23)
Psychological capability	Memory, attention and decision process	1.Alcohol 2.Tired 3.Holidays	“If I had a drank alcohol at the weekend, it would take Tuesday or Wednesday to get over it, and I wouldn’t want to eat this food” (female 40, higher education, FG1: P3) “Well ye know, if I have been out all day with the kids and I am tired, and I haven’t the slow cooker on, there’ll be a fast food takeaway then, and that’s the reality of it”. (female 40, higher education, I: P17) “And like holidays like Christmas, you just eat for the sake of it.” (female 41, higher education, FG1: P4)
Psychological capability	Behaviour regulation	1.Lack of monitoring of food consumption	“No, I don’t, and sure, when I go to weight watchers, I don’t even do it” (female 41, low education, I: P16) “No, but trying to be very aware of it, you know, but not recording it”. (female 40, low education, I: P14)
Physical capability	Skills	1.Lack cooking skills	“I couldn’t cook that, if you handed me all the ingredients, I would be like, what am I doing with it” (male 51, further education, FG2: P7) “No, I wouldn’t be confident, I can cook basic meals, but I am not very versatile with those foods on that diet”. (male 55, low education, I: P21).

COM-B, Capability, Opportunity, Motivation, Behaviour; TDF, Theoretical Domains Framework; FG1, focus group 1; FG2, focus group 2; I, interview; P, participant.