Table 3.

Summary of themes derived from the studies reviewed.

Aggregate Dimensions	Second-Order Themes and First-Order Concepts	Supporting Studies
Internal factors	Motivation as a facilitator
	Drive to improve health	36–42, 45, 47
	High intrinsic motivation	38, 44, 46
	Ready to make a lifestyle change	38, 41, 42, 44
	Weight loss success	36, 38, 45–47
	Experiencing personal benefits	36–39, 41, 47, 48
	Following a structured plan	40, 45–48
	Self-determination	36, 38, 41
	Involvement in a research study	36, 37, 39, 41, 47
	External motivation (e.g., family)	36, 37, 40, 49
	Loss of motivation as a barrier
	Lack of external accountability/supervision	42, 44, 46, 48
	Slower weight loss	39, 48
	Ambivalence around concrete strategies	38, 41, 45
	Weight loss no longer a priority	36, 45, 46
	Self-efficacy as a facilitator
	Utilising behaviour regulation strategies	37–39, 41, 44
	Increased perceived self-efficacy	39, 41, 42, 45, 49
	Improved behaviour awareness	40, 42
	Setting clear goals	40, 45, 46–48
	Self-monitoring	42, 45
	Acquiring new knowledge	37, 40, 42
	Low self-efficacy as a barrier
	Lack of self-regulation	36, 37, 39, 40, 44
	Low self-confidence	36, 37, 39, 44
Programme factors	Acceptability of diet/programme as a facilitator
	Convenience of diet/programme	39, 41, 47–49
	Programme tools/education facilitated adherence	40, 47, 48
	Flexible restraint	40, 43
	Unacceptability of diet/programme as a barrier
	Lack of variety/boredom	36, 39, 46–48
	Difficulties transitioning to real food	39, 48
	Too expensive	36, 37, 40, 46
	Did not match taste preferences	37, 39, 46
	Role of study staff as a facilitator
	Personalised support	36, 38, 39, 42, 47
	Accountability	36, 39, 40, 44, 45, 47, 48
	Trust in/rapport with healthcare professional	38, 40, 42, 43, 46–49
Social factors	Strong social support as a facilitator
	Group support/shared experience	39–41
	Supportive spouse/family/friends/colleagues	43, 45–47
	Poor social support as a barrier
	Unsupportive spouse/family/friends/colleagues	41, 44, 46
	Social expectations/pressures	40, 41, 44, 46
	Loss of group support	36, 41, 44
Environmental factors	External factors as a barrier
	Obesogenic environment	38, 39
	Reduced physical activity opportunities	36, 49
	Reduced capacity to overcome barriers	38, 42, 43, 49