Treatment adherence, defined as the degree to which the patient actively follows the plan of care, is very difficult for subjects undergoing ketogenic dietary therapies (KDTs). This is a relevant issue because adherence to dietary therapies is considered 1 of the primary determinants of the treatment's success. This paper aimed to review the literature evidence about KDT adherence according to age and diagnosis of patients. Performed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method, this systematic review included clinical trials and observational studies. The risk of bias was assessed by the RoB 2.0 Cochrane tool and the quality of evidence according to the Mixed Methods Appraisal Tool system. Twenty-two articles were included, with more than half (n = 12) having average quality (2-3 stars). The studies' heterogeneity in measuring adherence and diagnosis made it difficult to compare results. Mean adherence rates were 71.5%, 66%, and 63.9% for children, adolescents, and adults, respectively. Adherence and compliance rates varied according to the follow-up period (79.7%, 66.7%, and 37.7% at 6, 24, and 36 months, respectively). The most frequent reasons for low adherence were linked to inefficacy in seizure control, adverse effects, food refusal, difficulty in preparing KDT meals or diet restrictiveness, lack of motivation, poor parental compliance, or cost of the diet. To conclude, there is a lack of standardized tools to measure adherence. Several studies highlighted the families' challenges in adhering to KDTs. These factors should be considered when creating strategies and resources on family education.
Keywords: Adherence; Compliance; Ketogenic diet; Ketosis; Systematic review; Treatment adherence.
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