The search strategy identified 7980 records which were first screened by abstract and title; 472 articles were included for full-text screening, of which 25 articles were included (Fig. 1).

Flowchart for the screening and selection of studies

The study characteristics of the 25 included studies can be found in Table 1 (see Appendix S3 for additional information).

In total 572 HCPs were interviewed of which 42.7% were GPs, 29.4% practice nurses, 2.5% practice assistants, 7.9% dieticians and 0.52% physiotherapists [6, 21, 22]. Other studies also included health care directors and program managers [23], locality leaders [24] and health coaches (17.0%) [25] next to HCPs only. In most studies the participants were women [6, 21, 24, 26,27,28,29,30,31,32,33,34,35,36,37], though many studies did not report the sex of the participants [22, 23, 38,39,40,41].

Twenty of the included studies collected data by semi-structured individual interviews which were performed face-to-face or via telephone [21,22,23,24,25, 27,28,29,30,31, 34,35,36, 38,39,40,41,42,43], five studies conducted focus-group interviews [6, 26, 33, 37, 44], and one study combined questionnaire outcomes with interviews [32].

The interventions included weight management programs [21, 23, 32,33,34] including dietary and/or physical activity changes [6, 22, 24, 25, 28], addressing psychological health [31, 40], eHealth interventions including online guidance by HCPs [27, 41,42,43], and newly developed combined lifestyle interventions [36, 38, 39, 44]. Some interventions required a referral by GPs [26, 29, 30, 35, 37].

Most of the interventions focused on adults with overweight or obesity [6, 21, 22, 24,25,26,27,28, 31,32,33, 35,36,37, 40, 43, 44], six interventions were meant for children and their family [23, 30, 34, 38, 39, 41] and one focused on adolescents [29].

Total scores ranged from 6 to 10 with an average of 8.2 ± 1.0 (see Table 2). Most studies did not fulfil the criteria to report the relationship between the researcher and the participants (n = 17), did not clearly explain their recruitment strategy (n = 11) or insufficiently explained the data analysis (n = 10).

After thematic synthesis, 382 codes were identified and assigned to 323 marked quotations. These codes were grouped into seven themes, divided between barriers and facilitators. The seven main themes identified were logistical challenges to implement the intervention, intervention characteristics, support, patient-related factors, provider-related factors, financial resources and effectiveness of the intervention. The themes and codes with corresponding quotes are presented in Table 3.

Logistical challenges were mentioned as barrier for the implementation of lifestyle interventions in primary care by 16 studies [21, 22, 24, 26, 30,31,32,33, 35, 36, 38, 41,42,43,44]. The main challenges reported by HCPs were lack of time to provide the intervention, additional workload for HCPs and lack of staff available to provide the intervention. Lack of facilities such as no available room in practice and poor or no internet connection to provide online guidance were reported as barrier mainly by GPs and practice nurses.

Characteristics of the intervention were mentioned by 23 studies, of which 17 studies reported certain intervention characteristics as barriers [6, 23, 24, 26,27,28, 30, 32, 34,35,36,37,38,39, 41,42,43] and 18 reported facilitators [