Discussion:
The current study tested the utility of an intervention informed by an
integrated theoretical model to promote low-fat food consumption,
carbohydrate counting, and physical activity among adults with T2D in
Iran. This theory-based intervention could be adopted by chronic disease
health care professionals. Based on the results of earlier qualitative
formative research among the target population (Blinded for review), the
intervention focused on constructs from the TPB and risk perceptions and
planning factors from the HAPA. To our knowledge, this study comprises
the first formal evaluation of a theory-based intervention to promote
carbohydrate counting - a critical behaviour in diabetes management. The
results suggest that the intervention was successful in changing
behaviour and cognitions related to carbohydrate counting, showing some
support for the integrated model to inform behaviour change in this
context. However, it did not produce the expected changes for either
low-fat food consumption or physical activity. The intervention was only
successful in promoting the volitional construct of planning, but
behaviour and other cognitions remained unchanged. This may be due to
the nature of diabetes as a disease highly concerned with nutrition
behaviours such that people already associate a diabetes diagnosis with
a need to address any unhealthy eating patterns
(Yannakoulia, 2006) .
For carbohydrate counting, the intervention showed promise by
significant increases in behaviour, intention, PBC a,nd planning for
intervention participants over time compared to control participants,
with the improvements in carbohydrate counting behaviour at least
partially due to enhanced planning. These findings emphasize the
importance of including planning as a self-regulatory component in
behavioural interventions, reinforcing assertions that the impact of
cognitions on behaviour is mediated by planning
(Norman and Conner, 2005,
Sniehotta et al., 2005a,
Gellert et al., 2012). There were no
improvements over time among intervention participants for the
motivational phase constructs of attitudes, subjective norm, and risk
perceptions, but there was a significant change for PBC. This highlights
the importance of control perceptions and the need to consider barriers
to performance at both motivational and volitional stages of decision
making for carbohydrate counting.
The observed differences for carbohydrate counting, as opposed to
low-fat food consumption, may be due to the specificity of the
carbohydrate counting behaviour for diabetes management and to the
short-term acute symptoms resulting from non-compliance (leading to
abnormal blood glucose and, consequently, clinical outcomes). Further,
participants had completed the study inclusion requirement of diabetes
education, incorporating carbohydrate counting training. They so were at
least primed as to the importance and positive benefits of this crucial
diabetes management behaviour.
For physical activity, intervention participants showed an improvement
in their degree of planning for physical activity compared to control
groups but no other cognitions or activity behaviours. These findings
are in contrast to other TPB-related studies showing it to be an
effective basis for a physical activity behaviour change intervention
among adults with T2D (White et al.,
2012). The current study may have faced challenges in promoting
physical activity due to: (a) most participants were females who are
culturally less involved in physical activities, especially outdoor
exercise, and (b) >60% of participants had full-time jobs.
The commute in Tehran is often 3-4 hours/day, both barriers which may
benefit from direct targeting in future interventions.
The intervention significantly reduced TG levels by approximately 10
mg/dl but had no effects on LDL-c, weight, and BMI. Low-carbohydrate
diets have been shown to reduce TG rather than LDL-c
(Mahan et al., 2012,
Santos et al., 2012). As the only
behaviour change observed in this study was for carbohydrate counting.
Because carbohydrate counting restricts carbohydrate intake explicitly,
it seems reasonable to relate the reduction of TG to carbohydrate
counting behaviour. Congruently, a meta-analysis by Santos et al.,
showed that low-carbohydrate diets did not affect LDL-c
(Santos et al., 2012).