Motivation for diet and exercise management ... - Wiley Online Library

EMPIRICAL STUDIES

doi: 10.1111/j.1471-6712.2011.00884.x

Motivation for diet and exercise management among adults with type 2 diabetes Bjørg Oftedal RNT, Msc (PhD student)1, Edvin Bru Dr Philos (Professor)1,2 and Bjørg Karlsen RNT, MSc, PhD (Associate Professor)1 1

Department of Health Studies, Faculty of Social Sciences, University of Stavanger, Stavanger, Norway and 2Centre for Behavioural Research, University of Stavanger, Stavanger, Norway

Scand J Caring Sci; 2011; 25; 735–744 Motivation for diet and exercise management among adults with type 2 diabetes Aim: The aim of this study was to investigate diet and exercise management and how indicators of intrinsic motivation such as ability expectations and values are associated with diet and exercise management among adults with type 2 diabetes. Background: Motivational problems are probably one of the main reasons for poor diabetes management. However, the mechanisms involved in the motivation for adequate selfmanagement are still unclear. Design and methods: A cross-sectional design including a postal questionnaire that investigated diet and exercise management as well as intrinsic motivational factors such as ability expectations and values related to these behaviours was used to collect the data. A sample comprising 425 adults with type 2 diabetes aged between 30 and 70 completed the questionnaire. Results: Reported diet management was more in accordance with recommendations than reported exercise management. Yet results indicated equally high ability

Introduction Type 2 diabetes is a growing public health problem worldwide. At present, it is estimated that 285 million people suffer from diabetes, believed to be primarily a consequence of an ageing population, increased obesity and physical inactivity (1). Type 2 diabetes involves a complex, lifelong process requiring a large degree of selfmanagement on the part of the individual. Self-management refers to behaviours that include diet, exercise, blood

Correspondence to: Bjørg Oftedal, Department of Health studies, Faculty of Social Sciences, University of Stavanger, N-4036 Stavanger, Norway. E-mail: [email protected]

expectations and positive values for exercise and diet management. Moreover, results demonstrated that ability expectations and values explained more variance in exercise (21.6%) than in diet management (7.6%). Conclusions: The modest association between intrinsic motivational factors and diet management may imply that there are important extrinsic factors that play a significant role in determining dietary behaviour. The combination of lower exercise activity than recommended and high ability expectations and values for such activity may reflect that subjective exercise norms are formed individually in accordance with what most people recognise as the appropriate level of physical activity. Finally, results may indicate that there is potential for improving exercise management by stimulating intrinsic motivation as well as by more clearly communicating recommendations for such management. Keywords: ability expectations, adults, healthcare practitioners, motivation, type 2 diabetes, quantitative research, values. Submitted 12 April 2010, Accepted 21 December 2010

glucose monitoring and possibly the use of medication aimed at achieving adequate metabolic control and preventing long-term complications such as coronary heart disease, stroke, blindness, kidney failure and amputation (2, 3). As previous studies have found that diet and exercise management are especially difficult to attain and maintain (4–6), we selected these aspects for our study. A recent Norwegian survey demonstrated that only 7% of adults with diabetes achieved optimal metabolic control necessary for preventing complications (7, 8). Similar results have also been found in other countries (9). Previous research has suggested that motivational problems are probably one of the main reasons for poor diabetes management (10, 11). Although motivation has been found to be critical for self-management, only few studies have explicitly focused on this topic (12, 13). However, some studies have indicated that individuals who are primarily

Ó 2011 The Authors Scandinavian Journal of Caring Sciences Ó 2011 Nordic College of Caring Science

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motivated by external factors (i.e. external rewards) have less chance of attaining a healthy diet and maintaining physical activity, than those whose motivation is mainly intrinsic (14–16) (i.e. performing activities) because it is inherently satisfying or related to basic human needs. See e.g. Deci & Ryan (17). However, the mechanisms involved in motivation for adequate self-management are still unclear, and this study seeks to investigate how indicators of intrinsic motivational such as ability expectations and values are related to diet and exercise management among adults with type 2 diabetes.

Background Understanding why people act and think as they do constitute two fundamental research questions in general human motivation theory (18). This study is inspired by the expectancy-value theory developed by Eccles & Wigfield (19), which posits that individuals’ expectations and values are important determinants of their intrinsic motivation. Eccles (20) refined and extended the theoretical foundation of McClelland (21) and Atkinson (22) to include a broader array of psychological and social–cultural perspectives. Because theories within the expectancyvalue tradition are commonly used to explain health behaviours (23), we consider that this theory provides a valuable basis for the present research. According to Eccles (20), expectancy reflects a construct of both ability beliefs (individual’s evaluation of their competence in different areas) and expectancies of success (individual’s beliefs about how well they will do on an upcoming task). Theoretically, distinctions between ability beliefs and expectancies can be drawn, but empirically these two concepts are often strongly related (20). In this context, expectations refer to an individual’s beliefs about his/her ability to perform necessary diet and exercise management (ability expectations). It has been suggested that individuals are more motivated to seek challenging tasks (e.g. balancing diet and exercise) when they believe that they are capable of accomplishing them (24). Related constructs are prominent in other motivational models, in particular Bandura’s self-efficacy theory (25). The concept of self-efficacy has been widely used in the self-management research on chronic diseases (26) and has been consistently found to be associated with better self-management among people with type 2 diabetes (27–30). In contrast to ability expectations, values have played a less central role in research about self-management motivation among adults with type 2 diabetes. Values concern incentives or reasons for performing the activity, and the motivational potential is partly governed by what people consider important (19). For example, it may be assumed that when diabetes management is valued, individuals will devote more time to both planning and performing selfmanagement. However, values are influenced by different

components such as perceived utility and cost, which can affect behaviour (19). Utility is determined by the importance of a task in relation to current and future goals. For instance, people with type 2 diabetes exercise, because they wish to prevent long-term complications. The cost component is characterised as the negative aspect of engaging in a task. In our study, the cost component will be referred to as negative values related to diet and exercise management. Research among people with type 2 diabetes has suggested that the most frequent negative aspects of self-management are negative physical reactions, time constraints, lack of financial resources and performing tasks that they do not like (4, 5, 31, 32). However, Eccles & Wigfield (19) indicate that there is a link between expectancies and values. With regard to diabetes management, it can be assumed that individuals with a high level of belief about their ability to engage in exercise also value performing physical activities. On the other hand, if physical activity is perceived as too costly, the individual’s belief about being successful in diabetes management may decrease. In summary, although there is some research on expectancy beliefs in the form of perceived self-efficacy in type 2 diabetes, values have been somewhat neglected in both theoretical and empirical works on motivation for self-management. To date, we have been unable to find research that combines expectations of the ability to perform necessary management and values related to these behaviours among people with type 2 diabetes. This study is therefore unique because it examines how intrinsic motivational factors such as expectations and values are related to necessary diet and exercise management among adults with type 2 diabetes.

Aim The aim of this study was to investigate diet and exercise management and how indicators of intrinsic motivation such as ability expectations and values are associated with diet and exercise management among adults with type 2 diabetes.

Methods Design The study has a cross-sectional design and was conducted as the first step in a longitudinal, prospective survey. The data were collected in September/October 2008 by means of a postal questionnaire.

Data collection A total of 689 adults with type 2 diabetes aged between 30 and 70 were invited to participate in the study. The


Motivation for diet and exercise management participants were recruited from (i) seven general practitioners (GPs) in one large municipality as well as in some smaller ones in the south-western part of Norway and (ii) members of the Norwegian Diabetes Association. The second group recruited from the Norwegian Diabetes Association was selected from five Norwegian counties, strategically selected to represent cultural variations between Norwegian regions and settlement patterns (urban vs. rural). The sampling procedure was designed to give people with type 2 diabetes in the different subsamples an equal opportunity to be recruited to the study. Inclusion criteria were adults with type 2 diabetes who were aged between 30 and 70 and willing and able to complete a questionnaire written in Norwegian.

Ethical considerations The study was approved by the Norwegian Regional Committee for Medical and Health Research Ethics (No. 055.08), the Norwegian Social Science Data Services NSD and the Privacy Ombudsman for Research (No. 18770). Eligible patients attending the GPs and members of the Norwegian Diabetes Association were invited by letter to participate in the survey. Information about the study, the possibility to withdraw at any time, and the fact that confidentiality was guaranteed were included in the letter that accompanied the questionnaire. The questionnaires were returned to the researchers by post.

Instruments Dependent variables. Diet and exercise management. To cover the frequency of diet and exercise management performance, six items were selected from the 14-item Summary of Diabetes Self-Care Activities (SDSCA) developed by Toobert et al. (33). The SDSCA is a self-report measure for assessing the self-care activities of people with diabetes. The instrument has been extensively used in diabetes research and shown satisfactory reliability and validity (33). The respondents were asked about the frequency of performing diet (4 items) and exercise (2 items) management over the preceding 7 days. Examples of items are as follows: (i) ‘How many of the last 7 days have you followed a healthful eating plan?’ (ii) ‘On how many of the last 7 days did you participate in at least 30 minutes of physical activity? (Total minutes of continuous activity, including walking)’. Scores ranged from 0 to 7 points and higher scores indicated a greater frequency of performing diet and exercise management. The dimensionality of the items was tested by principal component analysis (PCA), the implementation of oblique rotation and the number of extracted components set to two. The latter was because of the fact that the six items were expected to measure two dimensions of self-management, namely diet and exercise management. This two-component solution explained

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39.5% (diet) and 20.5% (exercise) of the total variance, which had eigenvalues of 2.3 and 1.2, respectively. The item ‘On how many of the last 7 days did you eat high fat foods such as red meat or full-fat dairy products?’ yielded component loadings below 0.40 and was therefore not included in the two-component-based indexes that were computed for diet and exercise management. The index scores were calculated as mean scores across unweighted item scores. The diet and exercise subscales had a Cronbach’s alpha of 0.75 and 0.65, respectively. An a of 0.65 was considered acceptable for a two-item scale. Indicators of intrinsic motivation (independent variables). Ability expectations to perform necessary diet and exercise management were assessed by means of 12 items from the 20-item Diabetes Management Self-efficacy Scale for patients with type 2 diabetes (SE-Type 2) developed by van der Bijl et al. (34). These items are considered to cover expectations of the ability to perform diet and exercise management. The respondents are requested to indicate their ability expectations about these aspects. The items have a 5-point Likert scoring format with the following responses: ‘no, definitely not, ‘probably not’, ‘maybe yes/maybe no’, ‘yes, probably’, ‘yes, definitely’. Scores ranged from 1 to 5 and higher scores indicated greater expectations of the ability to perform necessary diet and exercise management. The dimensionality of the items was tested by a PCA, implementing oblique rotation and an eigenvalue of >1. Oblique rotation was selected because previous studies have found correlations between these types of expectations (35, 36). The principal component analysis yielded a two-component solution (see Table 1). The item ‘I think I’m able to select the right foods’ was not included in any subscale owing to its component loading of 1, was conducted to investigate the dimensionality of these items. Oblique rotation was selected because there are grounds for supposing that different kinds of management-related values will correlate (37). This component analysis yielded a


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B. Oftedal et al. Table 1 Results from principal component analyses of items assessing ability expectations to perform diet and exercise management

Factor loadings Subscale names and items

1

Diet ability expectations I think I’m able to adjust my diet when I am away from my home I think I’m able to follow my diet when I am away from home I think I’m able to follow my diet when I am on vacation I think I’m able to follow my diet when I’m at a reception/party I think I’m able to select different foods but stay within my diabetic diet I think I’m able to follow my diet most of the time I think I’m able to adjust my diet when I am under stress or tension I think I’m able to adjust my diet when I’m ill I think I’m able to select the right foods Exercise ability expectations I think I’m able to get sufficient physical activities, for example taking a walk or biking I think I’m able to take extra physical activities, when the doctor advises me to do so When taking extra physical activities. I think I’m able to adjust my diet Eigenvalues Explained variance (%): Total = 58.92 Cronbach’s alphas

2

0.89 0.88 0.87 0.74 0.69 0.58 0.57 0.44 0.38 0.91 0.85

5.5 46.3 0.88

0.58 1.5 12.65 0.78

Table 2 Results from principal component analyses of items assessing values of diet and exercise management values

Factor loadings Subscale names and items

1

Positive diet and exercise values Regular exercise helps/will help me to maintain a satisfactory weight The recommended diet helps/will help me to regulate my blood sugar Exercise helps/will help me to better regulate my blood sugar Regular exercise reduces the chances of developing long-term complications The recommended diet helps/will help me to maintain a satisfactory weight The recommended diet helps/will help me to avoid long-term complications Negative diet values The recommended diet is not very tasty The recommended diet is boring The recommended diabetic diet is challenging Eating the recommended food makes me feel different in social contexts Negative exercise values Regular exercise is too tiring Exercise makes/will make everyday life too hectic Exercise drains/will drain my strength Eigenvalues Explained variance (%): Total = 55.81 Cronbach’s alphas

three-component solution (see Table 2). The first component comprised six items concerning positive values related to diet and exercise management. The second component included four items associated with negative diet values, whereas the third component contained three items with negative exercise values. Components and component-based indexes were labelled accordingly (see Table 2 for Cronbach’s alphas for the component-based

2

3

0.75 0.72 0.72 0.69 0.69 0.66 0.81 0.81 0.75 0.65

3.62 27.87 0.79

2.23 17.18 0.77

0.84 0.78 0.72 1.40 10.76 0.70

scales). The solution with one component covering both positive diet and exercise values indicates that empirically it was not possible to differentiate between these two concepts. On the other hand, the separate components found for negative diet and exercise values indicate that it is relevant to distinguish between these concepts. Consequently, one single index score covering items assessing positive diet and exercise was computed, whereas


Motivation for diet and exercise management separated index scores were computed for negative diet and exercise values, respectively. In accordance with internationally accepted guidelines for the translation of instruments (39), the English items in the SDSCA and SE-Type 2 scale were translated into Norwegian and subsequently back-translated. Control variables. Demographic and clinical variables. Information about age, gender, disease duration and treatment regimen was collected. Age was scored as a continuous variable (in years). Gender was graded as follows: women = 1 and men = 2. Disease duration was scored as a continuous variable (in years). Treatment regimen was assessed by asking the respondents to indicate whether they were treated by means of diet, oral medication or insulin. Glycosylated haemoglobin (HbA1c) was determined by self-reports of the participants’ most recent HbA1c values. Body mass index (BMI) was calculated as weight in kilograms divided by height in metres squared. Both height and weight were self-reported.

Data analyses Data analyses were conducted using the SPSS 15.0 statistical package (version 15.0, SPSS Inc., Chicago, IL, USA) (40). The statistical analyses included descriptive statistics, principal component analysis, reliability testing, Pearson correlation coefficients and multiple linear regression analysis. Multiple linear regression analyses controlling for demographic and clinical data were used to explore the relation between motivational variables and diet and exercise management.

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Results A total of 425 persons with type 2 diabetes returned the questionnaire, resulting in a response rate of 62%. The respondents’ demographic and clinical data are presented in Table 3. The majority of the participants included in the research were men (53.9%), had at least secondary education (58.2%), treated by means of oral medication (55.8%) and had HbA1c levels within an acceptable range (7.0%). The mean age of the sample was 58.2 years. Participants who responded to at least 70% of the items in any scale were included in the study. Missing data were dealt with by giving a missing item the mean score of the other items in each subscale completed by the respondent. Thirty-nine respondents (mainly older persons, mean age 63.5 years, who reported a low educational level) were excluded because of more than 30% of data missing from one or more of the scales (see Table 3). The descriptive information pertaining to the two dependent and all the independent variables is presented in Tables 4 and 5. Approximately 25% of the respondents stated that they followed their diet 7 days a week, while 8% reported exercising daily. On the other hand, Table 5 illustrates that the majority of the respondents scored high on indicators of intrinsic motivation for healthy diet and physical activity. About 80% reported ‘yes definitely’ or ‘yes probably’ with regard to their belief in their own ability to manage to exercise. The same tendency was found in the subscale ‘Diet ability expectations’, where 70% reported that they expected to be able to follow their diet. According to the value scales, almost everyone (95.6%) agreed that a healthy diet and

Table 3 Response rate and characteristics of the samples recruited from GPs and Norwegian Diabetes Association (N = 386)

Invited Response Response after exclusion Response rate before exclusion (%) Response rate after exclusion (%) Demographic factors Men (%) Women (%) Age Mean ± SD (years) Disease duration mean ± SD (years) Clinical parameters HbA1c (%) BMI (kg/m2) mean SD Diabetes treatment Diet (%) Tablets (%) Insulin (%) Ó 2011 The Authors Scandinavian Journal of Caring Sciences Ó 2011 Nordic College of Caring Science

Sample from GPs

Sample from Norwegian Diabetes Association

Total sample

189 136 120 72 63.4

500 289 266 58 53.2

689 425 386 62 56

60 40 57.7 ± 8.6 6.6 ± 5.6

51.1 48.9 58.4 ± 8.8 8.7 ± 7.0

53.9 46.1 58.2 ± 8.6 8.1 ± 6.1

6.9 ± 1.1 30.5 ± 5.9

7.1 ± 1.0 29.4 ± 5.0

7.0 ± 1.1 29.7 ± 5.3

24.2 46.7 29.2

12.4 59.8 27.8

16.1 55.7 28.2

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Table 4 Percentages within sections of the scoring range (low seventh ‘‘0 day per week’’ to high seventh ‘‘7 days per week’’) mean scores and standard deviation for SDSCA (N = 386)

Diet management Exercise management

0 day per week (%)

1 day per week (%)

2 days per week (%)

3 days per week (%)

4 days per week (%)

5 days per week (%)

6 days per week (%)

7 days per week (%)

Mean

SD

2.8 16.6

5.4 18.1

7 21.8

7.5 20.5

15 4.7

14.8 7.8

23.8 2.6

23.6 8.0

4.71 2.67

1.77 1.93

Table 5 Percentages within sections of the scoring range (low fifth, ‘‘No definitely not’’/‘‘Disagree strongly’’ to high fifth ‘‘Yes definitely"/"Agree Strongly’’) mean scores and standard deviation for diet and exercise ability expectations and values of diet and exercise management (N = 386)

No, definitely not (%) Diet ability expectations Exercise ability expectations

0.5 1.3

Positive diet and exercise values Negative diet values Negative exercise values

Probably not (%) 4.4 2.8

Maybe yes/maybe not (%)

Probably yes (%)

Yes, definitely (%)

Mean

SD

22.8 15.3

47.4 29.8

24.9 50.8

3.76 4.10

0.70 0.79

4.50 2.54 2.31

0.57 1.01 1.02

Disagree strongly (%)

Disagree little (%)

Neither agree nor disagree (%)

Agree little (%)

Agree Strongly (%)

0.5 28.2 35.0

0.3 23.8 23.1

3.6 25.1 28.2

21.2 17.6 10.9

74.4 5.2 2.8

Table 6 Pearson’s correlation coefficient for intercorrelation between ability expectations to perform diet and exercise management, values of diet and exercise management, demographical and medical variables (N = 386)

Gender Disease duration Tablets Insulin Diet ability expectations Exercise ability expectations Positive diet and exercise values Negative diet values Negative exercise values

Age

Gender

Disease duration

0.03 0.25 ** )0.04 0.06 0.13 ** 0.12 ** 0.03 )0.13* )0.07

0.04 0.05 0.05 )0.18** )0.10 )0.15* 0.20** )0.04

0.07 0.42** )0.00 )0.07 0.07 0.01 0.05

Tablets

)0.12* )0.08 0.00 0.03 0.05 0.01

Insulin

Diet ability expectations

Exercise ability expectations

Positive diet and exercise values

Negative diet values

)0.04 )0.16** )0.10* )0.01 0.06

0.48** 0.11 )0.34** )0.21**

0.28** )0.19** )0.44**

)0.17** )0.28**

0.31**

*p < 0.05; **p < 0.01 (two-tailed).

regular exercise had a positive value for them. In contrast, relatively few participants reported that diet (22.8%) and regular exercise (13.8%) implied negative values for them. Table 6 presents the results from bivariate correlations between the independent and control variables included in the study. Significant correlations were found between ‘Diet ability expectations’ and ‘Exercise ability expectations’. Moreover, the former had significant negative correlations with ‘Negative diet values’ and ‘Negative exercise values’. The same tendency was found for ‘Exercise ability expectations’, which had significant negative correlations with ‘Negative exercise values’ and ‘Negative diet values’. In addition, significant positive correlations were found

between ‘Exercise ability expectations’ and ‘Positive diet and exercise values’. The results from the correlations between dependent variables and control and motivational variables as well as the multiple linear regression analyses for associations between these variables are presented in Table 7. As can been seen, all indicators of intrinsic motivation exhibited significant bivariate associations with diet and exercise management scores. Results from the multiple regression analysis revealed that among the indicators of intrinsic motivation only ‘Diet ability expectations’ yielded a significant positive multivariate association with ‘Diet management’ scores. ‘Exercise management’ showed significant multivariate associations with ‘Exercise ability


Motivation for diet and exercise management Table 7 Results from correlation (Pearson’s r) and multiple linear regression analysis (standardised beta weights (b) for associations between control variables, independent variables and diet and exercise management (N = 386)

Control variables Age Gender Disease duration Tablets Insulin Independent variables Diet ability expectations Exercise ability expectations Positive diet and exercise values Negative diet values Negative exercise values R2 R2 independent variables

Diet management

Exercise management

r

r

b

b

0.16** 0.12* 0.07 )0.26** )0.21** )0.11* 0.00 )0.02 )0.03 )0.09* )0.07 0.04* 0.02 0.05 )0.09 0.29** 0.23** 0.13**

0.16* 0.07 0.04

)0.24** )0.08 )0.17** )0.06 0.179 0.076

0.26** 0.42** 0.19**

0.03 )0.09 0.00 0.04 )0.02 0.09 0.26** 0.03

)0.09* 0.10 )0.38** )0.26** 0.241 0.216

*p < 0.05; **p < 0.01.

expectations’ and ‘Negative exercise values’, indicating that participants who reported higher exercise expectations had a greater level of regular physical activity. Ability expectations and values explained more variance in scores for regular physical activity (21.6%) than for diet (7.6%). A follow-up regression analysis with body mass index (BMI) included as an additional control variable was conducted. The inclusion of BMI in the regression model yielded only modest changes in beta-coefficients for the independent variables. Finally, the results revealed a nonsignificant association between a ‘Positive value of exercise and diet’ and ‘Exercise management’ and ‘Diet management’.

Discussion This study is one of only a few that has examined how ability expectations and values are associated with diet and exercise management among adults with type 2 diabetes.

Diet and exercise management One aim of this study was to investigate diet and exercise management among adults with type 2 diabetes. People with type 2 diabetes are expected to follow a healthy diet every day, and approximately 50% of the respondents stated that they adhered to their diet 6–7 days per week. On the other hand,