Short-term effectiveness of a theory-based intervention to promote diabetes management behaviours among adults with type 2 diabetes in Iran: A randomised control trial

Abstract

Background: Diet and physical activity are recommended for diabetes management. Evidence suggests theory-based interventions are more efficacious than non-theory approaches. This study aimed to test the short-term effectiveness of an integrated theoretical model-based intervention to encourage compliance for low-fat food consumption, carbohydrate counting and physical activity in adults with type 2 diabetes.

Methods: A 4-week parallel randomised control trial was conducted in Iran. Data were collected using a self-report questionnaire at baseline and 8-weeks post-intervention. This survey assessed the theory of planned behaviour (TPB) constructs of attitude, subjective norm (others' approval) and perceived behavioural control (PBC). We also assessed risk perceptions (motivational) and planning (volitional) from the health action process approach (HAPA). Furthermore, weight, body mass index, triglyceride (TG) and LDL-cholesterol were measured, with a sub-sample of participants providing haemoglobin A1c (HbA1c) assessments.

Results: For both low-fat food consumption and physical activity, only planning revealed a significant improvement over time for intervention rather than control participants (F = 8.78, P ≤ .001 for low-fat vs F = 11.26, P ≤ .001 for physical activity). For carbohydrate counting, significant effects were found for behaviour (F = 4.37, P = .03), intention (F = 8.14, P ≤ .001), PBC (F = 7.52, P ≤ .001) and planning (F = 4.54, P = .03), reflecting improvements over time in the intervention participants compared to controls. Furthermore, the effects of the intervention on behaviour were partially mediated via participants' degree of planning (B = 0.10, SE = 0.06, CI = 0.01 to 0.26). The serum TG level was significantly reduced from pre to post-intervention for intervention rather than for control participants (F = 18.69, P ≤ .001) as did Hb1Ac in a sub-sample of study participants.

Conclusions: This intervention showed promising short-term effects for carbohydrate counting but did not show improvements for low-fat diet nor physical activity. Given the improvement in psychological measures and self-reported behaviour for carbohydrate counting, coupled with the findings for TG, future research is needed to demonstrate longer-term improvements.

Keywords: carbohydrate counting; health action process approach; low-fat food consumption; physical activity; theory of planned behaviour; type 2 diabetes.