Methods

Trial design and Procedures

This randomized, crossover trial investigated the effects of ⁣a minimally processed⁢ food (MPF) diet⁤ versus an ultra-processed food (UPF) diet on weight change⁣ in adults with obesity.Participants completed two ‍in-laboratory dietary intervention⁣ periods of 14 days each, separated by a 14-day washout⁢ period. Randomization to the sequence of dietary interventions was stratified ⁢by sex, ethnicity, and nightshift status. During each intervention period,‍ participants consumed all meals and snacks provided by the research team, maintaining consistent macronutrient compositions across both diets. ‍Detailed descriptions of the dietary ‍interventions, food provision, and participant monitoring ⁤have been previously published [reference to previous publication, if applicable]. The study protocol adhered to the CONSORT 2010 statement: extension to randomised crossover trials [43]. No interim analysis was planned or ⁤conducted.

Participants

Adults aged 18-55⁣ years with a body mass ‍index (BMI) of 30-45 kg/m² were recruited from the London area via advertisements ⁣on social media and through NHS ‍partnerships. Key inclusion criteria included being generally healthy, not currently‍ following a restrictive diet, and willing to consume provided meals⁤ for the duration of the study. Exclusion criteria encompassed pre-existing medical conditions (e.g., type 1 diabetes, cardiovascular⁣ disease), current use of weight-loss medications, pregnancy or breastfeeding, and allergies or intolerances to foods commonly used in the dietary interventions. A ‍total of 18 participants were enrolled, and 16 completed both intervention periods.

Outcomes

the primary outcome was the ‍change in body weight from baseline to ‍the end of each intervention period. Secondary outcomes included⁤ changes ⁢in percentage body fat, waist circumference, energy⁣ intake, hunger and satiety ratings (assessed using visual analogue scales), and blood ‍biomarkers related to metabolic health⁢ (e.g., glucose, insulin, lipids). All outcome measures⁣ were assessed at baseline, after each intervention period, and at the end of the washout period.

Statistical Analysis

Data were analyzed using R⁣ v.2024.04.1+748. Statistical significance was set at P < 0.05. Crossover effects were assessed using linear mixed-effects models, ⁣with‍ participant as a random effect and intervention sequence as a fixed effect. The primary analysis focused on ⁤the effect of diet (MPF ⁣vs. UPF) on change in body weight, adjusting for baseline weight and stratification variables (sex, ethnicity, and nightshift status).

Handling Missing Data

The impact of missing data on ⁤the primary outcome analysis was assessed using multiple imputation with chained equations under the assumption of ‍data missing at ⁢random. Missing data ⁤for the primary outcome were ⁤first imputed using ‍model variables ‍(diet, randomization⁣ arm, nightshift status ⁤and available data for %WC), and ⁢then ⁣imputed using model variables and auxiliary baseline variables ⁢(diet,⁣ randomization arm, nightshift status, ⁤available data for %WC, ethnicity, sex, occupation, ⁣education, ⁤family history of obesity, ‍baseline estimated BMR, baseline energy intake and baseline weight). ⁣The impact of missing‍ data on the primary outcome analysis was also assessed using inverse ⁣probability weighting. Propensity scores for receiving the treatment (MPF diet or UPF diet) were first calculated using⁣ the randomization stratification variables: sex, ethnicity and nightshift status, and baseline estimated BMR, and then calculated ⁤using‍ randomization ⁣stratification variables and auxiliary baseline variables (randomization arm,‍ nightshift status, available⁤ data for %WC, ethnicity, sex, occupation, ⁣education, family ⁤history ‍of obesity, baseline estimated BMR, baseline energy intake and baseline weight). Stabilized weights were then used⁢ to reweight the remaining sample.

Secondary Outcome Analyses

Changes in secondary outcomes were ⁤analyzed using similar linear mixed-effects⁤ models⁢ as described for the primary outcome. As secondary outcomes in ⁢this study are exploratory⁤ in‍ nature, significance values⁢ were not adjusted for multiple comparisons. Any apparent significance of these⁣ results should be confirmed in future‍ research. Data were presented ⁣in tabular form using Microsoft Excel v.16.91 (24111020), and figures were⁣ created using Prism‍ 10 v.10.2.3.

Ethics

The Yorkshire and The humber-Sheffield Research Ethics Committee approved the trial on 22 December 2022 (22/YH/0281). The study was registered prospectively on ClinicalTrials.gov (NCT05627570). all⁤ participants provided written ⁢informed consent before any screening or research-associated measurement.

Patient and ⁢Public Involvement

NHS staff at UCLH provided⁤ input to the trial design following a focus group session. Obesity Empowerment ⁢Network UK members with lived experiance of obesity also contributed to the study design. One member of the trial