Table_2_My Diet Study: protocol for a two-part observational, longitudinal, psycho-biological study of dieting in Australian youth.docx

IntroductionSelf-directed dieting (i.e., unsupervised) is very common among adolescents and young adults but has had almost no direct research. This paper describes the protocol for the My Diet Study, a two-arm observational investigation of the natural progression of dieting among young people over a period of 6-months. The study aims to examine the links between self-directed dieting, general physiological and psychological metrics of wellbeing (e.g., depressive symptoms) and biomarkers of gut-brain axis functions (e.g., microbiome and hormones) that are predicted to influence diet adherence through appetite, mood and metabolism regulation.
MethodsYoung people aged 16–25, intending to start a diet will be invited to participate in this observational study. For Part 1 (psychological arm), participants will be asked to complete a set of questionnaires and diaries at the beginning of every month for 6 months, to assess overall mental (e.g., psychological distress, disordered eating) and physical (e.g., weight) health, perceived diet success, food intake and gastrointestinal movements. For Part 2 (biological arm), a subsample of 50 participants will be asked to provide feces, blood and saliva for bio-sampling each month for the first 3-months of their participation in Part 1.
DiscussionThe My Diet Study will be the first longitudinal, observational study of dieting in young people combining in-depth psychological and biological data. It is anticipated that the findings will yield psychological & biological information about the impacts and effectiveness of self-directed dieting in young people, inform a framework for advice on safety in dieting among young people and help to establish the potential for biomarkers for risk management and improvement of diet-based lifestyle interventions.

一、研究背景
自主节食（Self-directed Dieting，即无监督式节食）在青少年与青年群体中极为普遍，但目前几乎尚无针对该行为的直接研究。本研究详述了「我的节食计划（My Diet Study）」的研究方案：该研究为双臂观察性研究，旨在追踪6个月内青年群体节食行为的自然发展进程。本研究旨在探究自主节食与一般健康相关生理、心理指标（如抑郁症状），以及肠脑轴功能生物标志物（如微生物组与激素）之间的关联；上述指标被认为可通过食欲、情绪与代谢调节影响节食依从性。

二、研究方法
本观察性研究将招募计划启动节食的16至25岁青年作为研究对象。
1. 第一部分（心理评估臂，Psychological Arm）：研究对象需在参与研究的6个月内，于每月初完成一系列问卷与饮食日记，以评估其整体心理健康状况（如心理困扰、进食障碍倾向）、身体健康状况（如体重）、主观节食成效、食物摄入情况与胃肠道活动。
2. 第二部分（生物样本臂，Biological Arm）：从第一部分的研究对象中选取50名亚样本，要求其在参与第一部分研究的前3个月内，每月提供粪便、血液与唾液样本用于生物采样。

三、研究讨论
「我的节食计划（My Diet Study）」将是首个结合深度心理与生物数据的青年节食纵向观察性研究。本研究预期可获取青年群体自主节食的影响与效果相关的心理与生物信息，为青年节食安全指导框架提供依据，并助力确立可用于风险管理及优化基于节食的生活方式干预的潜在生物标志物。