Two review authors independently assessed the eligibility of the studies. They also assessed the risk of bias and extracted data using a modified version of the Cochrane Consumers and Communication Review Group data extraction template. Any discrepancies in judgement were resolved by discussion and consensus, or with a third review author. Because the studies differed widely with respect to interventions, measures of diet adherence, dietary advice, nature of the chronic diseases and duration of interventions and follow-up, we conducted a qualitative analysis. We classified included studies according to the function of the intervention and present results in a narrative table using vote counting for each category of intervention.