Poor eating habits are common during young adulthood and influence chronic disease morbidity. This systematic review evaluates the effectiveness of interventions aiming to improve dietary intake among young adults and, identifies which behaviour change techniques (BCTs) are most effective. Six electronic databases were searched for RCTs published until October 2018, and evaluating behavioural interventions assessing change in dietary intake in young adults (17–35 years). Of the 18,779 articles identified, 54 were included. Forty studies focused on fruit and/or vegetable intake, of which 63% showed a significant between-group difference in favour of the intervention group. Meta-analysis (n = 17) demonstrated a significant increase in fruit and vegetable intake of +68.6 g/day after three months of intervention and +65.8 g/day for interventions >3 months when compared to control. A meta-analysis (n = 5) on total energy intake found no significant differences between groups. The BCTs with the highest effectiveness ratio were habit formation (100%), salience of consequences (83%) and adding objects to the environment (70%). The review highlights the potential of behavioural interventions to improve young adults’ fruit and vegetable intake but was less convincing for other dietary outcomes. Due to the lack of studies including each BCT, the BCTs imperative to success could not be identified.

Young adulthood is associated with the highest rate of weight gain compared with any other adult age group. This review evaluates the effectiveness of interventions with adiposity outcomes among young adults and identifies which behaviour change techniques (BCTs) are most effective. BCT utilization was assessed using Michie's 93-item BCT Taxonomy v1. Six electronic databases were searched for randomized controlled trials assessing change in adiposity in young adults (17-35 years) until December 2019; identifying 21,582 articles. Fifty-one studies were included. Metaanalyses for weight (n=19 studies), body mass index (BMI) (n=20 studies), and waistcircumference (n=10 studies) demonstrated no significant between-group differences at ≤3 or >3 months. There were no differences between interventions focusing on weight loss or weight-gain prevention. Narrative synthesis showed significant between-group differences in weight change, favouring the intervention in 14/43 (33%) studies. In studies assessing BMI and waist circumference, this was 31% (11/36) and 25% (4/16). Two BCTs had a percentage effectiveness ratio >50% in weight loss interventions; social support (unspecified) and self-monitoring behaviour, and one in weight-gain prevention interventions; and goal-setting (outcome). Findings demonstrate initial potential for these types of BCTs and can help build cumulative evidence towards delivering effective, cost-efficient, and replicable interventions. K E Y W O R D S behaviour change, obesity, young adults

Background: Young adulthood has become synonymous with the development of poor lifestyle behaviours associated with an increased risk of preventable chronic disease in later years. Interventions aiming to improve health behaviours may be more engaging and effective if they are targeted to males or females than interventions with a gender-neutral approach. This review will examine the outcome effectiveness of gender-targeted and gender-neutral interventions targeting nutrition, physical activity or overweight/obesity in young adults (17-35 years). Methods: Six electronic databases were searched for randomised controlled trials (RCTs) published up to December 2019 that evaluated nutrition, physical activity and/or overweight/obesity interventions in young adults (17-35 years). An effective intervention was one where the change in one or more primary outcome was positive and statistically significantly different from baseline, compared with control, or if no control comparator, compared with another active intervention. Effectiveness of outcomes was compared between gender-targeted and gender-neutral studies.

Objective: To describe strategies used to recruit and retain young adults in nutrition, physical activity and/or obesity intervention studies, and quantify the success and efficiency of these strategies. Design: A systematic review was conducted. The search included six electronic databases to identify RCTs published up to 6th December 2019 that evaluated nutrition, physical activity and/or obesity interventions in young adults (17-35 years). Recruitment was considered successful if the pre-determined sample size goal was met. Retention was considered acceptable if ≥80% retained for ≤6-month follow-up or ≥70% for >6-month follow-up. Results: From 21,582 manuscripts identified, 107 RCTs were included. Universities were the most common recruitment setting used in 84 studies (79%). Less than half (46%) the studies provided sufficient information to evaluate whether individual recruitment strategies met sample size goals, with 77% successfully achieving recruitment targets. Reporting for retention was slightly better with 69% of studies providing sufficient information to determine whether individual retention strategies achieved adequate retention rates. Of these, 65% had adequate retention. Conclusions: This review highlights poor reporting of recruitment and retention information across trials. Findings may not be applicable outside a university setting. Guidance on how to improve reporting practices to optimise recruitment and retention strategies within young adults could assist researchers in improving outcomes.

Migraine is the third most common condition worldwide and is responsible for a major clinical and economic burden. The current pilot trial investigated whether ketogenic diet therapy (KDT) is superior to an evidence-informed healthy “anti-headache” dietary pattern (AHD) in improving migraine frequency, severity and duration. A 12-week randomised controlled crossover trial consisting of the two dietary intervention periods was undertaken. Eligible participants were those with a history of migraines and who had regularly experienced episodes of moderate or mildly intense headache in the previous 4 weeks. Migraine frequency, duration and severity were assessed via self-report in the Migraine Buddy© app. Participants were asked to measure urinary ketones and side effects throughout the KDT. Twenty-six participants were enrolled, and 16 participants completed all sessions. Eleven participants completed a symptom checklist; all reported side-effects during KDT, with the most frequently reported side effect being fatigue (n = 11). All completers experienced migraine during AHD, with 14/16 experiencing migraine during KDT. Differences in migraine frequency, severity or duration between dietary intervention groups were not statistically significant. However, a clinically important trend toward lower migraine duration on KDT was noted. Further research in this area is warranted, with strategies to lower participant burden and promote adherence and retention.