Table 1.

Summary of excluded research studies related to the application of the theory of planned behaviour (TPB) to obesity.

Source	Sample	Study design	Measurements	Results
Payne et al. (2004)	286 UK employees in a company	Cross-sectional survey	(1) Intention to exercise (number of hours of exercise); (2) exercise behaviour (type of exercise and the time taken to complete the exercise); (3) intention to eat healthy (7-point scale); (4) healthy eating behaviour (7-point scale); (5) attitude (five semantic differential items, each with a 7-point scale); (6) subjective norm (7-point scale); (7) PBC (6 items derived from a study by Sparks et al. (1997), each with a 7-point scale); perceived need (single item with a 7-point scale).	For exercise, PBC had the highest correlation with intention (r = .43, p < .001). Attitude and the subjective norm explained 14% of the variance in intention and PBC explained 10%. For healthy eating, attitude had the highest correlation with intention (r = .47, p < .001). Attitude and the subjective norm explained 27% of the variance in intention and PBC explained 2%. Perceived need failed to account for further variance in exercise, but accounted for a further 3% variance in healthy eating.
Gardner and Hausenblas (2005)	117 overweight women	Cross-sectional survey	(1) BMI; (2) waist-to-hip ratio; (3) personal history; (4) TPB questionnaire: four measures of attitude (7-point scale), six belief-based measures of attitude (7-point scale), three measures of the subjective norm (7-point scale), three measures of PBC (7-point scale), 1-item measure of intention; (5) exercise behaviour by exercise class attendance; (6) diet behaviour by daily adherence to ±100 calories of the 1500-calorie goal.	The direct measure of PBC was the only significant determinant of exercise intention (β = .69, p < .001). Intention did not explain the significant variance in exercise behaviour (p = .19). PBC contributed significantly to diet intention (β = .28, p < .05). However, intention did not explain a significant amount of the variance in diet behaviour.
Duangchan et al. (2010)	21 overweight or obese schoolchildren aged 9–11 years with a BMI-for-age ≥ 85th percentile	A pre–post-experimental design without a control group	(1) Knowledge about obesity-related Type 2 diabetes (15 questions); (2) healthy eating behaviour (11-item food questionnaire); (3) healthy eating self-efficacy (questionnaire with 11 items, each with a 5-point scale); (4) healthy eating self-control (questionnaire with 14 items, each with a 5-point scale); (5) BMI.	DM knowledge, healthy eating self-efficacy, healthy eating self-control and healthy eating behaviour significantly increased from the baseline. However, BMI significantly decreased from the baseline only for healthy eating intervention. The BMI mean was not significantly different when combined with the physical activity intervention.
Plotnikoff et al. (2013)	560 overweight and obese adolescents from 37 school boards	A self-administered Web-based survey	(1) Brief constructs of TPB: attitude (2-item measure with 5-point semantic differential scales for each measure), subjective norm (a single item with a 5-point scale), PBC (4 items, each with a 5-point scale), intention (a single item with a 5-point scale); (2) physical activity with the Physical Activity Questionnaire for Older Children (PAQ-C) (Kowalski et al., 1997). Responses were given on a 5-point scale, with higher scores representing greater physical activity levels.	Significant intercorrelations (p < .01) were observed among the tested TPB constructs. All of the tested constructs were associated with physical activity (p < .01).

PBC: perceived behavioural control; BMI: body mass index; DM: diabetes mellitus.