Chronic diseases are the leading cause of mortality worldwide. Although the adoption of a healthy diet is recognized as an important component for their prevention and management, many individuals at risk of or having chronic diseases do not adhere to recommended dietary advice. The methods used to facilitate changes in dietary habits through dietary advice (defined in this review as 'interventions') could improve adherence of clients to dietary advice. Therefore, we reviewed trials of interventions aiming to enhance adherence to dietary advice for preventing and managing chronic diseases in adults.
We identified 38 studies involving 9445 participants examining several types of interventions for enhancing adherence to dietary advice for preventing and managing many chronic diseases. The main chronic diseases involved were cardiovascular diseases, diabetes, hypertension, and renal diseases. Interventions shown to improve at least one diet adherence outcome are: telephone follow-up, video, contract, feedback, nutritional tools and more complex interventions including multiple interventions. However, these interventions also showed no difference in some diet adherence outcomes compared to a control/usual care group making the results inconclusive about the most effective intervention to enhance dietary advice. Interestingly, all studies including clients with renal diseases reported at least one diet adherence outcome showing a statistically significant difference favouring the intervention group, no matter which intervention was provided. The majority of studies reporting a diet adherence outcome favouring the intervention group compared to the control/usual care group in the short-term also reported no significant effect at later time points. Studies investigating interventions such as a group session, individual session, reminders, restriction and behaviour change techniques reported no diet adherence outcome showing a statistically significant difference favouring the intervention group. Finally, interventions were generally of short duration, studies used different methods for measuring adherence and the quality of the studies was generally low.