Short-term outcomes of the digital combined lifestyle intervention CooL-MiGuide: a descriptive case series study

Background

The objective of this study is to investigate the changes over time in anthropometrics, behaviours and health perceptions over eight months of participation in the Combined Lifestyle Intervention (CLI) CooL-MiGuide. This intervention is a digital version of the Coaching on Lifestyle (CooL) intervention with the add-on of a digital platform and an app. Longitudinal data were collected between January 2022 and December 2023 from adults, mainly in the South-Western area of the Netherlands. All participants met the inclusion criteria for the CLI, which include being obese (Body Mass Index (BMI) > 30) or being overweight (25 < BMI < 30) with comorbidity and/or increased waist circumference; and being sufficiently motivated. We collected comprehensive data at baseline (T0) and after eight months of participation (T1) on anthropometrics, control and support, physical activity, diet attentiveness, alcohol consumption, smoking, perceived fitness, sleep and stress. Changes over time were analyzed using paired t-tests comparing T1 to baseline and effect sizes were calculated using Cohen’s d.

Results

The results indicate positive changes after eight months in anthropometrics, sedentary time, diet attentiveness, sleep, stress, fitness, and perceived health of in total 129 participants. The largest effect sizes were observed for weight (Cohen’s d = 0.62, average weight loss of 3.82 kg), perceived health (Cohen’s d = 0.58) and perceived fitness of the participants when waking up and during daytime (Cohen’s d = 0.41 and 0.52 respectively).

Conclusions

CooL-MiGuide participants exhibited improvements in perceived health and weight. The digital version of CooL can be a valuable alternative for people who prefer to participate from a location of their choice.

Trial registration

Dutch Trial Register NTRNL6061 (13-01-2017). Registered at Overview of Medical Research in the Netherlands (OMON), via https://www.onderzoekmetmensen.nl/.

In 2022, 50.2% of Dutch adults aged 18 years and older were overweight and 15.1% were obese [1]. Obesity is classified as a disease according to the World Health Organisation and the Dutch Health council [2, 3] for which an integrated approach, including physical activity and nutrition, is indicated as proper treatment [4, 5].

A Combined Lifestyle Intervention (CLI), eligible for reimbursement from standard health care in the Netherlands, is a health intervention designed for individuals with overweight or obesity, guiding them towards a healthier lifestyle. The term ‘combined’ refers to the fact that several lifestyle topics are included covering at least physical activity, healthy diet and/or behavioural change [5]. Complementary to these topics, sleep and stress are considered essential themes of the treatment of obesity and included in the CLI [6,7,8].The timespan of a CLI is two years usually offering both group and individual sessions [9].

Since January 2019, Combined Lifestyle Interventions (CLIs) have been part of basic health insurance in the Netherlands, making them standard care for eligible individuals (those who are obese with a BMI > 30 or overweight with a BMI between 25 and 30) combined with comorbidity and/or increased waist circumference; and sufficiently motivated).

The Coaching on Lifestyle intervention (CooL) is one of six CLIs approved and accredited by the Dutch Institute for Public Health and Environment (in Dutch: Rijksinstituut voor Volksgezondheid en Milieu) for effectively facilitating weight reduction.

Ehealth is denoted a priority and enabling factor for efficient, affordable and sustainable health care [10]. The Dutch ehealth monitor shows widespread use of ehealth in the Netherlands but this use mainly concerns patient portals and e-consultations [11] - digital CLIs are still in their infancy. Previous research on digitalized weight interventions show that they can be a viable and cost-effective alternative [12] providing outcomes comparable to face-to-face interventions [13, 14] thereby supporting easy access and convenience for both coaches and participants [15]. Important focus points for digital interventions are coverage by health insurance [11] as well as tailored content and human contact [13, 14].

Typically, CooL is offered face-to-face, but a digital version of CooL was a previously planned development, noted in earlier CooL-research [16]. In digital mode, CooL was expected to both benefit coaches and participants in easy access and convenience [15] whereas similar results of the digital intervention where to be expected compared to CooL delivered in physical mode [17, 18]. The COVID-19 pandemic necessitated a preliminary shift to digital delivery [16], thereby accelerating the planned development of a digital version of CooL. As a result, CooL-MiGuide was launched during the pandemic and continued afterwards at the request of CooL-referrers, care groups and CooL-participants. From the perspective of participants, the digital version of CooL is user-friendly, less time consuming and appeals to certain groups such as those providing informal care or childcare, less mobile individuals or those with irregular work hours or locations) [19].

Until now, no research has been done on the effectiveness of CooL-MiGuide. Our hypothesis was that CooL-MiGuide results in similar changes as the physical CooL-intervention [17, 18]. This hypothesis was based on the fact that important preconditions for effective digital interventions were covered in CooL- MiGuide. First, by means of the structured set-up and content of CooL-MiGuide [17], similar to the frequently studied CooL intervention. Second, by frequent contact moments including personalized feedback [20]. Third, by a high degree of feedback on personal behaviour and progress [21]. In addition, the participants of CooL-MiGuide deliberately choose to participate in the digital variant as it best fits their needs.

The objective of this study is to investigate the effect of a digital version of CooL on the changes over time in anthropometrics, behaviours and health perceptions after eight months of participation. Clarity on these changes over time is needed to support the inclusion of CooL-MiGuide in basic healthcare in the Netherlands besides the nationwide implemented regular CooL-intervention.

CooL

CooL aims to enhance perceived quality of life, healthier eating habits, more physical activity, less sedentary behaviour, attention for high quality sleep and relaxation, leading to positive physical outcomes such as weight loss, and a decrease in waist circumference. The program’s monitoring focuses on perceived health and weight as the primary outcomes.

The theoretical rationale behind CooL is based on the Environmental Research framework for weight Gain prevention [22] and rooted in the intervention-specific CooL Logic Model. The CooL Logic Model has been translated into end goals on skills and insights that participants gain after the two-year CooL-intervention and into a set of essential active elements that need to be ensured by the CooL-coaches in implementation. Via OSF a short description in Dutch is available on the end goals and essential active elements of CooL (https://doi.org/10.17605/OSF.IO/FER7T).

CooL consists of an intake session (1 h), an eight-month behavioural change phase (phase 1) and a sixteen-month follow-up phase (phase 2). The intervention includes individual sessions and 16 group sessions (1.5 h each), all led by the same coach. Both phases feature eight group sessions with phase 1 having a higher session density than phase 2. An indication of the planning of the group and individual sessions over the timespan of two years is displayed in Fig. 1.

Indication of group and individual sessions in CooL-intervention

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CooL-coaches are trained and licensed professionals who guide participants in taking responsibility for their personal lifestyle changes by addressing motivation, personal objectives and behaviour change. Participants are encouraged and supported to become more self-directed and manage their health-related behaviours by identifying, planning, and implementing personal health actions. The primary goal of CooL is to coach participants to achieve and maintain a healthier lifestyle tailored to their individual needs and goals. An overview of the content of CooL per phase is available as supplementary material (Additional File 1). In addition, a detailed description of the CooL-intervention and data collection method is available in the protocol [23].

CooL-MiGuide: a digital version of CooL

CooL-MiGuide is a digital version of the CooL-intervention pursuing the same aims as CooL. In CooL-MiGuide, all sessions are offered in digital modus (videoconferencing) and participants can make use of a supporting MiGuide-app and MiGuide-portal offering synchronous and asynchronous communication options with the CooL-coach and other group members, facilitating and stimulating mutual contact. In addition, the MiGuide-portal provides additional sources of information that are easily and at any time accessible, whereas the MiGuide-app provides participant specific information and challenges.

For CooL-MiGuide, additional inclusion criteria apply, e.g., participants must be digitally skilled, master the Dutch language and be in possession of a smartphone and laptop, tablet or computer. Participants that apply for CooL-MiGuide but do not meet these additional inclusion criteria, as noticed by both participant and staff during the introductory phone call, are referred back to their general practitioner for participation in CooL (with face-to-face sessions) or other suitable care.

The working elements of CooL-MiGuide are for the major part similar to CooL. The similarities and differences in working elements between both versions have been thoroughly investigated and are elaborated in detail [24]. The CooL-MiGuide coach pays specific attention to working elements that may differ from the physical mode of the intervention, mainly related to the interaction between coach and participant(s) and among participants, i.e., experiential learning, mutual connection, and cooperation. Additionally, the regional connection of CooL-MiGuide and local health and welfare organizations, as well as the connection with local sport facilities requires extra attention. On the other hand, CooL-MiGuide offers additional working elements compared to CooL, by offering additional cues to action (via prompts, invitations to challenges, the use of behavioural diaries and self-measurements in the MiGuide-app and MiGuide-portal), more (digital) contact moments and more flexibility through participation from a location of choice (e.g. home, workplace).

CooL-MiGuide complies with high quality and privacy standards by being certified in NEN 7510 and ISO 27001.

Study design and population

Since CooL is part of regular health care for eligible individuals, using a control group with no treatment would be unethical as it would mean withholding standard care. Therefore, a descriptive case series study is the most suitable research design in the current Dutch context.

CooL-MiGuide was launched during the COVID-19 pandemic, when temporary changes to CLI-regulations, allowed CooL to be offered digitally as well as face-to-face [25]. Both delivery modes continued post-pandemic, which makes it possible to look simultaneously at outcomes of both delivery modes of CooL.

Participants, all Dutch-speaking adults living in the Netherlands, were enrolled from January 2022 until December 2023, at various locations mainly in the (South-)Western Netherlands.

Power

The average effect size on the change in perceived health and weight in prior CooL-related research (0.52 and 0.56 respectively [16, 26]was used as input for the power analysis. Based on d = 0.52 for a difference between two dependent means, a two-tailed t-test with an alpha of 0.05, and a minimal power of 0.80, the minimal required sample size is 32 participants.

Data collection

For CooL-MiGuide-participants the same questionnaire used for CooL- participants, was administered. A printable version of the CooL Questionnaire is available via OSF in English and Dutch (https://doi.org/10.17605/OSF.IO/FER7T).

The collected outcome measures included the categories anthropometrics, control and support, physical activity, diet attentiveness, alcohol use and smoking, perceived fitness, sleep and stress.

Due to the online format of CooL-MiGuide, participants measured their own anthropometrics (i.e. body weight and waist circumference) following instructions provided by the CooL-coach on how to perform both measurements accurately. The use of the MiGuide-application encourages participants to take additional anthropometric measurements between sessions to monitor their progress.

Control and support were assessed by items covering self-mastery and social support and by using Likert response scales [27]. The constructs on physical activity, diet and perceived fitness were defined in cooperation with the Dutch Association of Lifestyle coaches (BLCN) with the objective to map behavioural change with a minimum set of questions. Physical activity was recorded in sitting minutes per day, differentiating between the least and most active days and in physical active minutes. Diet attentiveness was measured by items covering attentiveness of meal composition, food quantity and consumption and was also measured using Likert response scales. Alcohol use and smoking were quantified based on reported consumption. Perceived fitness was assessed by items covering health, fitness upon waking, daytime fitness and stress impact on daily functioning and by using Likert response scales. Sleep was evaluated with a shortened version of the PSQI-questionnaire [28] while stress was measured with the Dutch version of the Perceived Stress Scale [29]. Detailed descriptions of the questionnaire and anthropometric measurements are available in the protocol [23].

Data collection for CooL-MiGuide from all participants is centrally organised, thereby preventing bias in the selection of participants with positive changes only. It takes place at three points during the intervention: at the beginning of the intervention, during the intake (T0); after 8 months at the completion of phase 1 of the intervention (T1); and after 24 months at the end of the intervention (T2). A total of 807 adults started with CooL-MiGuide between January 2022 and December 2023, the timeframe used for data collection. In total 210 adults completed phase 1 of CooL-MiGuide before 2024 of which 129 adults returned the T0 and T1 questionnaires, resulting in a response rate of 61%. This response rate could have been potentially much larger as we had to use a strict cut-off date for data inclusion, enforced by a rigid deadline for delivering (primary) results needed for the accreditation process of CooL-MiGuide for inclusion in basic healthcare. A flow chart of the data collection is presented in Fig. 2.

All participants met the inclusion criteria for a CLI, except one (n = 1, 0.78%) whose BMI and waist circumference at baseline were below the inclusion threshold, likely due to lifestyle changes between application and the start of CooL. However, since the waist circumference of this participant was above the threshold at referral, this case was included.

Data from T2 were not yet available at the time of analysis and are not presented in this article.

Flowchart of the data collection CooL-MiGuide

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Analyses

Variables were recoded according to the validated questionnaires methodology to facilitate the interpretation of outcomes (i.e., direction of effect sizes). We conducted an exploratory factor analysis and calculated McDonald’s omega to assess the internal structure of the constructs using R software [30]. These analyses supported summarizing the constructs by their item score means. Descriptive analyses (e.g., means, standard deviations) were performed for all items and constructs. Changes in outcome measures over time were analysed using paired t-tests (T1 versus T0). Effect sizes were calculated using Cohen’s d based on the standard deviation of the change scores. Outcomes were interpreted following Lipsey’s guidelines: an effect size smaller than or equal to 0.32 is considered small, 0.33 to 0.55 is considered medium and 0.56 or above is considered large [31]. Effect sizes are presented such that positive values indicate change in the desired direction while negative values indicate change in the undesired direction.

The target for the CLI (including CooL and CooL-MiGuide) to be deemed successful, is a 5% weight loss after the two-year intervention, as established by the Dutch Healthcare Institute (Dutch: Zorginstituut) based on guidelines from the Dutch Institute for Quality in Health Care (Dutch: Centraal Begeleidingsorgaan) and the National Institute for Health and Care Excellence [5]. This study covers only the first eight months of CooL-MiGuide, with 16 months remaining to achieve further weight loss. We categorized weight change outcomes into: 5% or more weight loss, 0 to 5% weight loss, weight stabilization, or weight gain.

Ethics

This study was conducted in accordance with the guidelines of the Declaration of Helsinki, submitted to and approved by the Research Ethics Committee of the Faculty of Health, Medicine and Life Sciences of Maastricht University (FHML-REC/2019/073). All participants were given the opportunity to ask questions or report any safety issues or concerns. They provided written informed consent, before starting with CooL, allowing their anonymised personal data to be used for research purposes.

In the results section all outcomes are presented beginning with the demographics of the participants (Table 1), followed by outcome measurements (Table 2), including mean values, standard deviations, intervals for changes in outcomes, and effect sizes.

Demographics

Data were collected from all CooL-participants as CooL is part of basic healthcare. A total of 129 adults started with CooL-MiGuide between Februrary 2022 and May 2023, the timeframe used for data collection. These participants completed phase 1 of CooL-MiGuide before 2024 and returned the T0 and T1 questionnaires. The amount of missing data varied per item and time of measurement (range 0.8–8.5%).

Most participants were female, had a Dutch background and lived with a partner with or without children. Additionally, most participants were employed and had an intermediate level of education (Table 1).

Anthropometrics

Weight, BMI and waist circumference all showed a decrease after eight months (T1) compared to baseline (T0). The average BMI of the participants was 36.6 at baseline and decreased by 1.3 BMI-points at T1. The average weight loss was 3.8 kg at T1, corresponding to a 3.5% average weight loss per participant after eight months. 28% of the participants lost over 5% of their body weight by T1, 52% of the participants showed weight stabilization or up to 5% weight loss, whereas 17% of the participants showed weight gain at T1 compared to T0 with 3% missing data. The average waist circumference decreased from 115.5 cm at T0 to 113.3 cm at T1. The change in waist circumference demonstrated a small effect size (Cohen’s d = 0.28) at T1, while weight and BMI showed large effect sizes at T1 (0.62 and 0.63 respectively).

Control and support

Self-mastery and social support showed no changes at T1 compared to baseline.

Physical activity

Sedentary time decreased at T1 for both the least and most active days of the week: participants sat on average 40 min less on the least active days and 46 min less on the most active days, compared to baseline. The effect size for sedentary time was small (between 0.23 and 0.31). The average daily active minutes showed no changes at T1 compared to baseline.

Diet attentiveness, alcohol and smoking

Over time, participants showed an increase in attentiveness to meal composition, awareness of food quantities and attentiveness when consuming food. The effect sizes for these items were medium (0.36, 0.37 and 0.34 respectively) when comparing baseline to T1.

At T1, 74% of participants indicated a healthier or much healthier eating pattern, 25% indicated no change and 1% ate less healthy compared to baseline. Alcohol consumption and smoking showed no change at T1 compared to baseline, although the number of smokers decreased from eight to six between baseline and T1.

Perceived fitness

The indicators for perceived fitness -perceived health, feeling fit when waking up, feeling fit during the day and the impact of stress on daily functioning- all showed improvements. The effect size was small for the impact of stress on daily functioning (0.23), medium for feeling fit when waking up and during the day (0.41 and 0.52, respectively) and large for perceived health (0.58).

Sleep and stress

Both constructs sleep and stress showed improvements at T1 compared to baseline, with small effect sizes (0.27 and 0.22, respectively) in the desired direction.

This is the first study on CooL fully offered in digital mode in combination with the MiGuide-app and MiGuide-platform. The results of CooL-MiGuide show positive changes in self-reported anthropometrics, behaviours (sedentary time, diet attentiveness) and perceptions (sleep, stress, fitness, and health) of the participants after eight months. Largest effect sizes were found on weight/BMI, and perceived health. Medium effect sizes were found on diet attentiveness and perceived fitness.

The set-up, approach and content of CooL is adopted in CooL-MiGuide, ensuring a similar intervention, enabling comparison on delivery mode. When comparing CooL-MiGuide with earlier research on CooL, a notably similar pattern in outcomes is visible: small to medium effect sizes in behaviours and awareness, and relatively large effect sizes in weight and perceived health [16, 32].

When comparing the outcomes of CooL and CooL-MiGuide to similar interventions in other countries, it is noticed that both CooL and CooL-MiGuide show positive results in all lifestyle domains addressed, whereas the majority of other interventions show changes over time in only a few areas (for example diet or physical activity) [33].

Matching the CooL-MiGuide outcomes to international research, the CooL-MiGuide results look promising showing weight loss that is equal in terms of effect size or larger than comparable interventions [13]. This is in line with our expectations as CooL-MiGuide meets the preconditions for effective digital interventions such as a structured set-up and evidence-based content (similar to CooL) [17], frequent (human) feedback loops, and the combination of personal coaching and content in line with personal needs [14, 20, 21].

Attention is needed for long(er) term behavioural maintenance and the prevention of drop-outs in CooL-MiGuide [17], as generating and continuing engagement might be more challenging in a digital environment [21]. The aspect of social support though, considered a strong driver for behaviour modification, is often under strain in an environment without physical interaction [21], but sufficiently covered in CooL-MiGuide. Further research could shed light on this interesting topic.

The effect size concerning waist circumference (0.28) is smaller than the effect size concerning weight (0.62) and is also smaller compared to earlier research on CooL [16, 32]. Preferably, waist circumference measurements are done by professionals, as is the case for CooL, since these measurements require a strict protocol, training and repeated measurements [34]. Measuring waist circumference accurately on an occasional basis by non-professionals is challenging. For CooL-MiGuide these measurements were carried out by participants themselves, potentially creating a larger margin of error. Still, a change can be detected, as demonstrated by the outcomes of CooL-MiGuide, but is simply more difficult to capture (i.e., reduced sensitivity). The weight measurements, done by the participants themselves on ordinary home equipment, generate lower reliability as well, but potential deviations in the equipment are unlikely within the timeframe of eight months.

CooL-MiGuide-participants reported to have reduced their sedentary time and felt more fit when waking up and during the day, whereas on physical activity (PA) no effect was visible. The results, a decrease in sedentary time and limited or no effect on PA, the latter in combination with large confidence intervals, are in line with earlier research on CooL [16]. Requesting input on minimum bouts of PA of 10 min, as well as the general perception of PA (i.e., being intensive) might raise barriers for registration. However, the decrease in sedentary time is already promising, as sedentary time is likely to be displaced by light intensive activity, generating a positive impact on health [35]. A finding that seems to be supported in this study by the improved outcomes on all constructs of perceived fitness for CooL-MiGuide-participants.

The CooL-MiGuide-sample, compared to previous studies on CooL, shows a similar gender distribution, but contains more participants with a non-Dutch background, more participants who are single, with a job and participants with an intermediate-level of education. Participants with a lower level of education are less represented. A process evaluation on the CooL-MiGuide-implementation in June 2023 showed that as much as 92% of the applicants for CooL-MiGuide effectively started with the intervention [19]. Reasons for not starting were mostly independent of the delivery mode of CooL-MiGuide (insufficient knowledge of Dutch language, dislike for group sessions, no motivation for intensive program) and partly related to the digital version (disliking digital interventions). However, research on a larger number of participants is needed to shed light on the sociological differences between participants attracted by the different delivery modes of CooL. Thereby keeping in mind that not all eligible individuals will be able or willing to join a digital intervention, emphasizing the importance of the continuing availability of the physical CooL-intervention [36].

The complementary offering of CooL-MiGuide might positively impact the motivation of the participants. Providing participants with a choice between a physical or digital delivery mode, contributes to the perception of self-control and autonomy and assures a better fit with the participants needs and wishes thereby preventing dropout and enhancing motivation to participate.

Strengths and limitations

This study has several strengths. Firstly, a broad scope of data is collected. Secondly, this ongoing research on CooL provides the opportunity to investigate an intervention in (daily) practice. Thirdly, we were able to investigate a topical and innovative adaptation of an existing evidence-based intervention which enables further testing, development, implementation and scale-up.

There are also some limitations in this study. To begin, CooL-MiGuide does not yet offer nationwide coverage though quite some regions are already in scope. Secondly, due to the digital mode of delivery, the anthropometrics are collected by self-measurement thereby generating a larger margin of error than measurements done by professionals. Thirdly, the lack of a control group limits the interpretation of the conclusions, though it still provides valuable insights on the potential of the intervention in an applied context.

Recommendations for future research

We recommend future research on CooL-MiGuide to address the following topics:

• Study on the long-term effects of the CooL-MiGuide intervention (i.e., including 24 months measurements).

• Study on the characteristics of the participants that are appealed by the digital version of CooL and participants that are not, as well as on the characteristics of participants that drop-out of CooL-MiGuide, in order to maximize digital inclusion when scaling up the intervention.

• Study on the overall dropout rates of CooL when offering the choice between physical and digital mode of CooL.

• Study on the social cohesion within a CooL-MiGuide group of participants compared to similar interventions offering face-to-face contact moments and its impact on the outcomes of the intervention.

CooL-MiGuide-participants show relevant short-term changes in the essential constructs of perceived health and weight. The digital version of CooL can be a valuable alternative to physical combined lifestyle interventions for people who prefer participation from a location of their choice.

Supplementary Information.

The datasets generated and/or analysed during the current study are not publicly available. The raw data used for the research on CooL contains privacy-sensitive information on anthropometrics, perceptions and behaviors. CooL-participants sign an informed consent in which they grant access to their (anonymized) data for research purposes concerning evaluation, effect studies and further development of the CooL-intervention. In case a request to the corresponding author matches aforementioned purposes, the request will be qualified as reasonable and access to the raw data will be provided.

BMI:

Body Mass Index

CLI:

Combined Lifestyle Intervention

CooL:

Coaching on Lifestyle

PA:

Physical activity

The authors like to thank the MiGuide Organization, CooL-MiGuide-coaches and the CooL-MiGuide-participants for their efforts to make this research possible.The continuously ongoing data collection on CooL provides comparable datasets for the various studies on CooL. As a result, there is overlap not only in the description of the intervention but also in method, approach and outcomes, leading to textual overlap, despite the use of an overarching protocol article. To avoid this overlap, ChatGPT (for IOS 1.2024.037 (19790)) was used to generate texts with similar meaning but slightly different wording.

Not applicable.

1. Nicole Philippens and Ester Janssen contributed equally to this work.

Authors and Affiliations

1. Department of Health Promotion, NUTRIM, Institute of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, the Netherlands

   Nicole Philippens, Ester Janssen & Stef Kremers

2. Department of Health Promotion, CAPHRI, Care & Public Health Research Institute, Maastricht University, Maastricht, the Netherlands

   Rik Crutzen

Contributions

Conceptualization, N.P., E.J., R.C. and S.K.; Methodology, N.P., E.J., R.C. and S.K.; Validation, R.C. and S.K.; Formal Analysis, N.P., E.J. and R.C; Investigation, N.P. and E.J.; Data Curation, N.P. and E.J.; Writing—Original Draft Preparation, N.P. and E.J.; Writing—Review and Editing R.C., and S.K.; Visualization, N.P. and E.J.; Funding Acquisition, not applicable. Both E.J. and N.P. contributed equally to the study. All authors have read and agreed to the published version of the manuscript.

Corresponding author

Correspondence to Nicole Philippens.

Ethics approval and consent to participate

This study was conducted in accordance with the guidelines of the Declaration of Helsinki, submitted to and approved by the Research Ethics Committee of the Faculty of Health, Medicine and Life Sciences of Maastricht University (FHML-REC/2019/073). All participants gave written informed consent, prior to starting with CooL, for their anonymised personal data to be used for research purposes.

Consent for publication

Not applicable.

Competing interests

Not applicable for S.K. and R.C. Both main authors (E.J. and N.P.) are co-owner of the CooL-intervention.

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