One Size Does Not Fit All: Complexity of Lifestyle Interventions in Primary Care T2D Prevention – Supporting Weight Loss and Weight Loss Maintenance

Abstract

Type 2 Diabetes (T2D) is a growing public health problem with potentially severe consequences for those affected. An unhealthy diet leading to being overweight combined with a sedentary lifestyle is considered a significant risk factor in the development of T2D. Changes in lifestyle, especially in diet and physical activity behaviors enabling sustained weight loss, can support T2D prevention. Changing lifestyle behaviors can, however, be challenging. Many individuals perceive intervention attendance and adherence as challenging. Behavioral interventions in T2D prevention are complex due to multiple interactions between intervention components and participants. This chapter discusses intervention complexity, mechanisms, and social-cognitive characteristics in T2D prevention interventions aiming for sustained weight loss. Social-cognitive factors refer to diverse attributes that may influence the success of behavior change. Here, self-efficacy, goal attainment, and participants’ sex and socioeconomic status are discussed. Challenges and potential solutions in designing and delivering T2D prevention interventions in primary care are reflected.

1. Introduction

T2D is a significant public health issue that can have severe consequences for those affected [1].

This chapter discusses the complexity of interventions for T2D prevention through lifestyle changes. It explores how the complexity of the interventions can affect their effectiveness. Additionally, this chapter discusses social-cognitive factors that can impact behavior change and intervention outcomes. Social-cognitive factors discussed in this chapter include self-efficacy, goal attainment, and participants’ sex and socioeconomic status. Research has shown that lifestyle change interventions can effectively prevent T2D [2, 3]. However, it is essential to note that these interventions may also increase health inequalities [4, 5]. This is because women and individuals with higher socioeconomic status are often overrepresented among participants, even though men, ethnic minorities, and those from lower socioeconomic backgrounds have a higher risk of T2D and would benefit significantly from lifestyle interventions [4, 6, 7, 8]. Therefore, it is essential to ensure that T2D prevention programs are accessible to all individuals, regardless of background. Finally, this chapter reflects on the challenges of designing and delivering T2D prevention interventions to achieve sustained weight loss in primary care and potential solutions.

2. T2D and prevention

T2D is a growing public health concern, with an estimated global prevalence of 6.1% [1, 9]. This is expected to double by 2050 [1, 9]. A combination of reduced insulin secretion and increased insulin resistance causes T2D. The development of T2D is preceded by prediabetes, an intermediate stage between normal glucose metabolism and T2D [10, 11]. T2D is a chronic condition that worsens over time, leading to physical damage and poorer health outcomes [12]. Over time, T2D can have serious consequences, including lasting damage to the cardiovascular and nervous systems. Individuals with T2D are at an increased risk of nerve impairments, including loss of feeling in extremities like feet due to nerve damage. They also have an increased risk of cardiovascular incidents such as stroke due to damage to the cardiovascular system [13]. Consequently, T2D is associated with higher societal and individual costs and lower quality of life among those affected [9, 14]. Therefore, prevention of T2D in primary care is essential to improve individual and population-level health [14, 15].

The primary risk factors for developing T2D include being overweight or obese, along with a sedentary lifestyle. In particular, an unhealthy diet that leads to overweight and obesity, combined with a lack of physical activity, is considered to be a key factor that increases the risk of developing T2D [2, 16]. However, the risk of developing and the progression of T2D can be modified through preventive lifestyle interventions. Research has shown that lifestyle interventions can potentially change the course of T2D by slowing, stopping, or even reversing the disease progression [17, 18, 19, 20]. Several studies have suggested that sustained weight loss can have potential benefits in preventing T2D. Consequently, lifestyle interventions are commonly recommended in the prevention of T2D. These interventions focus on achieving and maintaining a healthy weight through diet and physical activity changes [2, 21, 22, 23]. However, despite the benefits, many people find sustained weight loss challenging [2, 21, 24].

Primary prevention of T2D refers to efforts to prevent the risk factors for developing T2D from emerging, thus reducing the likelihood of developing T2D [25]. This type of prevention is often aimed at the population level, including health education and campaigns targeting the population more widely [25]. Here, prevention is used to refer to secondary and tertiary prevention among high-risk populations such as those with prediabetes (secondary prevention) or those already diagnosed with T2D (tertiary prevention) [25, 26]. Individuals with prediabetes have a high risk of progressing to T2D, while those with diagnosed T2D are at increased risk of adverse health outcomes. Individuals with prediabetes or T2D are vulnerable to disease progression and have a higher likelihood of gradually worsening health outcomes [25, 26]. This chapter discusses lifestyle interventions for those with prediabetes or T2D, encouraging weight loss and maintenance to slow, stop, or reverse the disease progression [17, 18, 19, 20].

Although lifestyle interventions have significant potential in preventing T2D, certain limitations may constrain their efficacy. There are certain limitations that can affect the outcome of an intervention. These limitations arise due to self-selection by attendees and participants leaving the intervention before its completion [21, 27]. However, despite these challenges, complex and multidisciplinary lifestyle interventions have shown promise in supporting sustained weight loss for T2D prevention in primary care and are considered a cost-effective approach [1, 27, 28]. Effective design and delivery of T2D prevention programs based on lifestyle changes requires evidence-based and theory-based information for public and primary healthcare providers [29, 30]. In addition, since the effectiveness of lifestyle interventions in the real world often falls short of the efficacy observed in trial conditions [31], primary care providers require knowledge about intervention pathways, that is, how the intervention produces the desired outcomes and how the characteristics of the target population may interact with the intervention pathways and outcomes [32].

3. Complexity in behavioral lifestyle interventions in T2D prevention

Complexity in behavioral lifestyle interventions refers to the various components of an intervention and the interactions between and within these components, which ultimately shape the outcomes of the intervention [33, 34]. Intervention components include techniques utilized to modify behaviors, the targeted population, the location of the intervention, personal factors, intensity, formats such as individual or group interventions, and time of day [33, 34]. The interactions within and between these intervention components can be either anticipated or unforeseen, but they all play a role in determining the intervention’s outcomes [33, 34]. For instance, an anticipated interaction between intervention components could be the relationship between the selected intervention location and the target population. Locations with easy access to public and private transportation will be more accessible to a larger group of individuals within the target population than remote locations that are primarily accessible by private means of transportation. On the other hand, unforeseen interactions may refer to unexpected participant group dynamics that either facilitate or hinder the achievement of the intervention’s outcomes. An example of intervention complexity is shown in Figure 1.

Figure 1.

Example of complexity in behavioral T2D prevention intervention. Adapted from [30, 34, 35, 36].

Developing a healthier and sustainable diet and physical activity habits is crucial in preventing T2D [2]. However, creating new health behaviors can be challenging. Therefore, behavioral intervention for T2D prevention is complex, involving multiple interconnected components that can affect the desired outcomes [30, 34]. Like other complex healthcare interventions, preventive interventions for T2D must consider the complexity within and between the intervention, social structures, and environment in which the behavior change occurs [37, 38, 39]. It can be a daunting task trying to make sense of this complexity while designing preventive T2D interventions. Therefore, it has been suggested that identifying and describing effective and adaptable behavior change techniques (BCTs) and intervention mechanisms [40, 41, 42] could improve the design and delivery of behavioral interventions for T2D prevention [30, 43]. Intervention mechanisms refer to the processes through which the BCTs deployed in an intervention are expected to impact the targeted behaviors [27]. In other words, intervention mechanisms describe how the selected BCTs (e.g., knowledge) are expected to impact behavioral determinants (e.g., beliefs about ability) that affect the performance of specific behaviors, which, in turn, influence the likelihood of performing a behavior such as physical activity [43].

Improved identification of the BCTs that are best suited to impact defined behavioral determinants has facilitated the identification of intervention mechanisms and thus enhanced the design of behavioral interventions [44], including those in the prevention of T2D. As described above, behavioral mechanisms explain how selected BCTs are expected to facilitate changes in behavioral determinants. For example, a BCT, such as increasing skills, can facilitate improved self-efficacy, which, in turn, facilitates changes in behaviors, such as physical activity, that lead to desired outcomes such as sustained weight loss [43]. In behavioral lifestyle interventions, self-efficacy is seen as a central behavioral determinant that describes individuals’ beliefs about their ability to perform goal-related behaviors and overcome obstacles [45, 46]. A behavioral mechanism explains how skills training, BCT can improve self-efficacy, increasing the probability of engaging in physical activity. Therefore, improving physical activity skills is expected to increase the likelihood of performing physical activities. This, in turn, supports weight loss in T2D prevention interventions [43, 44]. However, despite carefully planned intervention mechanisms, unexpected interactions between the deployed BCTs and the participating individuals may create unforeseen mechanisms that hinder or facilitate achieving the intended outcomes [43, 47].

In the prevention of T2D, a combination of physical activity and dietary changes that result in sustained weight loss is crucial [48]. Many behavioral interventions for T2D prevention encourage participants to alter their behaviors to promote a healthier diet and physical activity, leading to sustained weight loss [21]. However, despite weight loss benefits, many intervention participants struggle to achieve long-term weight loss [49, 50]. It is suggested that using an intervention theory, which involves planning intervention mechanisms based on behavioral theories, can improve the transparency and effectiveness of interventions [30, 51]. However, even though the existing behavior change theories can provide a framework for theory-based behavioral mechanisms in T2D prevention, a clear theoretical framework is often not articulated at the intervention design stage, which can hinder later evaluation of intervention effectiveness ([32], e.g., [52, 53, 54]).

4. Research to practice transfer of preventive T2D lifestyle interventions

T2D prevention often occurs in primary care, where primary care providers are responsible for designing and delivering preventive interventions. However, primary care providers may have limited expertise in adapting complex behavioral intervention research in primary healthcare practice [43, 55]. Researchers are not commonly involved in designing and delivering T2D behavioral interventions within local primary healthcare systems [56]. Primary care practitioners are left to infer research results for practical use. Therefore, it is crucial to have readily available information about effective intervention mechanisms and BCTs that can be efficiently utilized in practice. Without this information, research to practice transfer in T2D prevention may be significantly hindered, as primary care practitioners may struggle to adapt research into practical behavioral interventions within local primary care systems [57, 58, 59]. This is why the importance of intervention theory is highlighted, as it can provide clear and easily accessible information about effective intervention features [34]. It is common for behavioral interventions to perform better in experimental settings than when applied in everyday healthcare environments due to the challenges practitioners face in interpreting and replicating research into practice [31].

5. Social-cognitive attributes in preventive T2D lifestyle interventions

Social-cognitive attributes refer to individual characteristics such as age, educational achievement, employment status, family situation, intentions, beliefs about consequences, and self-efficacy. These attributes vary among individuals, over time, and in different situations and can impact the success of T2D prevention interventions [60, 61]. T2D risk is not equally distributed among different demographics. People with male sex, non-Caucasian ethnicity, and lower socioeconomic status are at a higher risk of experiencing adverse consequences from T2D. Unfortunately, these characteristics are associated with a lower likelihood of intervention enrolment and a higher likelihood of intervention cessation in T2D lifestyle interventions [4, 5, 8, 62, 63]. This presents a challenge for designing T2D prevention interventions. It requires addressing cognitive factors like self-efficacy and social support during behavior modification and considering characteristics such as age and sex that can influence behavior modification [54, 61].

Encouraging attendance and adherence to interventions is crucial to ensure the best possible chances of achieving the intended outcomes [35, 46]. Different social-cognitive factors may be involved in individuals’ decisions to attend an intervention and later adhere to it. These factors may include fear of T2D consequences and increased self-efficacy to cope with lifestyle changes. Interactions between the diverse factors and intervention components mean that the same social-cognitive factors may directly and indirectly influence intervention success [34, 64, 65]. Intervention design should consider strategies that encourage enrollment and reduce cessation, both influenced by social-cognitive characteristics [8, 35].

Here, the focus is on how social-cognitive factors, BCTs, and behavioral mechanisms influence participants’ engagement in T2D lifestyle interventions and success in achieving sustained weight loss. In this regard, factors such as mood and stress, which may also affect the success of the intervention, are not discussed here [65, 66, 67, 68]. Furthermore, this chapter does not aim to provide an in-depth analysis of the various social-cognitive factors, BCTs, or intervention mechanisms as described in different behavior change models and theories ( [69], e.g., [70, 71, 72]). Instead, this chapter discusses social-cognitive variables of self-efficacy, goal achievement, and participants’ sex and socioeconomic status.

5.1 Self-efficacy in preventive T2D lifestyle interventions

Self-efficacy is considered one of the key mechanisms in behavior change due to its role in regulating feelings, thinking, and, ultimately, behaviors [69]. In various theoretical models, such as the Theory of Planned Behavior [73], the Social Cognitive Theory [74], or the Transtheoretical Model (TTM) [75], self-efficacy has a central role. Self-efficacy refers to an individual’s belief in their ability to overcome obstacles while striving toward their goals [54]. Various studies have shown that self-efficacy plays a significant role in achieving and maintaining weight loss [45]. Higher levels of self-efficacy have been linked to increased physical activity in T2D prevention interventions, leading to better weight loss outcomes [47, 76]. Building new lifestyle habits is easier with strong self-efficacy [22, 74]. Therefore, T2D prevention interventions typically aim to improve self-efficacy to develop and maintain healthier physical activity and diet behaviors, thus increasing the likelihood of successful weight loss outcomes [21, 43]. Figure 2 presents an intervention mechanism with self-efficacy as an example.

Figure 2.

Overview of an intervention mechanism targeting physical activity behaviors. Adapted from [34, 44].

It is important to note that self-efficacy is not a single concept. In lifestyle change interventions, it can be differentiated between action and coping self-efficacy [54]. Action self-efficacy refers to the willingness to initiate new behaviors, while coping self-efficacy pertains to maintaining new behaviors despite challenges and setbacks [54, 77]. During the initial stages of lifestyle interventions, action self-efficacy is more important as it enables individuals to form new behaviors. Conversely, coping self-efficacy is central to maintaining newly formed behaviors despite challenges such as work and family commitments [78].

Many behavioral interventions in T2D prevention face challenges in retaining participants [2, 35, 79], especially those with family and work commitments [78, 80]. This often leads to missed opportunities for individuals to receive support in achieving their intervention goals, such as sustained weight loss [78]. Improving self-efficacy is essential in addressing this issue and ensuring that intervention participants maintain new behaviors despite challenges and barriers until they become habits [80]. However, influencing behaviors through self-efficacy may be challenging as research has suggested that for many intervention participants, self-efficacy is already high initially, leaving limited room for improvement [76, 81].

Moreover, high self-efficacy at the start of an intervention does not necessarily translate to success in achieving behavioral goals, such as weight loss [47, 76]. Instead, accessing the support offered by an intervention appears to moderate success in weight loss and weight loss maintenance. Regular intervention attendance has been linked to better weight loss outcomes, not necessarily by increasing self-efficacy [78, 82, 83], but by taking advantage of the support provided by the intervention [76].

5.2 Goal achievement in preventive T2D lifestyle interventions

Personal goals, such as achieving sustained weight loss, can be beneficial in increasing intervention attendance and achieving intervention objectives. Unrealistic goals can cause psychological distress and hinder progress [71]. Successful participation in a behavioral T2D prevention intervention that supports weight loss and weight loss maintenance necessitates accepting these intervention goals [84]. While goal setting is an effective BCT, unattainable goals can be distressing [44, 71, 85]. The distress caused by unattainable goals can lead to disengagement from goals, resulting in worse weight loss outcomes [71]. Engaging and disengaging from goals is called the adaptive self-regulation of goal adjustment, which enables lessening the impacts of unattainable goals [86, 87]. In the first phase, individuals disengage from an unattainable goal by withdrawing their efforts and commitment. In the second phase, individuals re-engage their efforts toward goal attainment elsewhere, such as in work or family pursuits [86].

Individuals often start a T2D prevention intervention with the personal goal of achieving weight loss and weight maintenance targets as specified in the intervention. However, failing to achieve these goals is not uncommon [11, 88]. In such cases, the ability to disengage from unattainable goals is self-protective and lessens emotional distress [86, 87]. However, this can hinder weight loss and weight maintenance efforts. Primary care professionals delivering the interventions must consider whether weight loss and weight maintenance goals are realistically achievable for the individuals. Instead of disengaging, adapting goals may be more beneficial, even if the magnitude of the goals is lesser than initially aimed.

While the ability for goal adjustment has been associated with improved health outcomes, ceasing efforts toward a goal without re-engaging with a new goal can lead to lower mental well-being [71, 87]. This situation can cause unfavorable health consequences [67, 88], whether for individuals’ physical or psychological health. Tendency to goal adjustment does not appear to be associated with an individual’s sex. However, those with higher Body Mass Index (BMI) at the start of a T2D prevention intervention, as well as those from ethnic minority backgrounds, may be at greater risk of disengaging from goals when unsure of their ability to achieve the intervention goals [89].

The examples of self-efficacy [69] and goal adjustment [71] demonstrate the complex interconnectivity of mechanisms of behavior change in the prevention of T2D. Therefore, it is essential to carefully consider the target populations, aims, and intervention mechanisms when designing and delivering preventive interventions in primary care to optimize weight loss outcomes [90]. While it may not be practical to create separate weight loss and maintenance interventions for every individual, interventions should still be designed to anticipate and respond to the needs of individuals, particularly those at higher risk of struggling with the demands of the intervention [91, 92].

5.3 Socioeconomic status and sex in preventive T2D lifestyle interventions

A self-selection bias may influence the decision to participate in a lifestyle-based T2D prevention intervention. In other words, those with higher self-efficacy regarding the expected lifestyle changes are more likely to enroll. Despite the expected ability to cope with the intervention challenges, many participants who have decided to enroll still require support to complete the intervention [54, 93]. Numerous studies have investigated how factors such as socioeconomic status and participants’ sex impact decisions to participate in type 2 prevention interventions. For instance, individuals belonging to an ethnic minority group and those having a lower socioeconomic background are at a higher risk of developing T2D. However, they may be underrepresented in preventive interventions [5, 35, 94]. Those who are younger have a lower degree of education, higher BMI, lower self-efficacy, or are unemployed are likelier to stop attending lifestyle interventions [35, 62, 95, 96]. This suggests that lifestyle interventions may need to focus on promoting attendance and adherence, particularly for individuals with the characteristics identified above, as part of diabetes type 2 prevention efforts. It appears important to consider ways to support participation among at-risk populations, especially those with lower socioeconomic status, when designing and implementing T2D prevention interventions [97, 98, 99].

It is recognized that attributes such as socioeconomic status can be estimated using different methodologies (e.g., [100]). However, the highest degree attained is often used to measure an individual’s socioeconomic status [101, 102, 103]. Socioeconomic status is a multidimensional concept encompassing occupation, education, and lifetime income [103, 104]. Education level is important to social and health inequalities in T2D prevention [8, 99]. It is essential that individuals from at-risk populations with lower socioeconomic status can benefit just as much from T2D prevention interventions as those with higher socioeconomic status. However, individuals with lower SES may face more limited resources that make it challenging to participate in preventive interventions [99, 103, 104]. Limited resources can include time, money, and health literacy. Health literacy refers to the knowledge and understanding of the role of lifestyle changes in the prevention of T2D. Therefore, the design and delivery of preventive interventions should ensure that individuals with lower socioeconomic status will not be excluded, potentially increasing their risk of experiencing worse health outcomes [63, 103, 105].

While women with higher educational attainment, that is, higher socioeconomic status, tend to be overrepresented in T2D lifestyle interventions, it is important to note that participant’s sex may not be associated with intervention attrition after a decision to participate is reached [8, 27]. Being a man with a lower degree of education is considered a risk factor for less favorable intervention outcomes in T2D prevention [4, 106, 107]. However, studies have also implied that women with a higher degree of education may also experience less favorable intervention outcomes [47, 78]. Overall, the degree of education and sex can moderate the relationship between individual participants and intervention outcomes, but the pathways are complex [4, 63]. Although women with higher socioeconomic status may be overrepresented in lifestyle interventions to prevent T2D, there are indications that higher socioeconomic status may be counterproductive for women. In particular, women with a university education and family responsibilities may be at risk for suboptimal intervention outcomes [8, 78]. This is especially true when women experience insufficient family support for their weight loss efforts [78].

6. Discussion

Preventive interventions have demonstrated potential in improving health outcomes among individuals with prediabetes or T2D [3]. However, despite the benefits of lifestyle changes in T2D prevention, interventions may experience challenges in attracting and retaining participants [35]. The design and delivery of primary care interventions are often challenging due to difficulties in adapting experimental intervention designs into primary care practice [57, 58], impacting the intervention’s effectiveness in everyday practice. The adaptation process can be further hindered by the complexity of the intervention when there is a lack of clarity on how the intervention causes the observed outcomes, that is, what the intervention mechanisms are [30, 34]. Without a well-founded understanding of intervention components and pathways, primary care providers may encounter difficulties in adapting experimental intervention designs to local primary care systems. These challenges may arise from interactions with different intervention components [30]. Different intervention components can, for example, unexpectedly interact with participants and ultimately affect the outcomes.

Furthermore, clearly formulated intervention mechanisms are needed to lessen challenges in designing and delivering behavioral interventions. A lack of clearly formulated intervention mechanisms may lead to uncertainty about how desired outcomes should be achieved [34, 44]. This also hinders the replication of the intervention into other contexts [34]. Primary care providers may have limited resources to interpret various intervention mechanisms from research studies. This places the responsibility on researchers to provide a clear presentation of intervention mechanisms, which is crucial for effectively adapting complex behavioral interventions for practice [108].

Designing and delivering weight loss interventions for T2D prevention could be improved by enhancing the multidisciplinary approach and partnerships between primary healthcare practice and research [109, 110]. Partnerships between primary care and research institutions may cover research initiatives and research to practice transfer collaborations [57, 110]. Additionally, as sustained weight loss in T2D prevention can be difficult, participants may benefit from involvement in and access to a multidisciplinary team of healthcare professionals during intervention delivery.

To ensure that as many as possible may benefit from lifestyle T2D intervention, it may be necessary to use different approaches to encourage at-risk groups to participate and encourage continuing participation. Individual attributes like the participant’s sex and socioeconomic status can affect the success of weight loss and weight loss maintenance for T2D prevention. However, by considering the mechanisms of behavior change and intervention and participant characteristics, it is possible to design interventions that are more likely to attract participation and encourage successful outcomes. Decisions to participate result from complex interactions between intervention components, individuals, and context variables [30, 111]. In other words, effective intervention design in primary healthcare requires considering which intervention is appropriate for whom and under what circumstances [112].