The Effect of Flexitarian, Time-restricted Eating on Cardiometabolic Traits in Normal Weight, Young Men (FlexiFast)

The Effect of Flexitarian, Time-restricted Eating on Cardiometabolic Traits in Normal Weight, Young Men

The Effect of Flexitarian, Time-restricted Eating on Cardiometabolic Traits in Normal Weight, Young Men: a Factorial Randomized Controlled Trial (FlexiFast Study)

The goal of this factorial randomized controlled trial is to find out whether time-restricted eating and flexitarian diet (on its own and combined) can improve cardiometabolic health markers in normal weight, young men with metabolic abnormalities? Participants will be assigned to four groups: control, flexitarian, time-restricted eating and time-restricted eating + flexitarian. Investigators will look for men with elevated fasting blood glucose or blood lipids level or blood pressure and with normal body weight and waistline. Participants from the flexitarian group will be asked to follow a diet that has been carefully designed for them by the PI and dietitian for the period of 8 weeks. Participants from the control group will receive general healthy eating recommendations. We aim to investigate if the experiment had any effect on changes in metabolic, inflammation and nutritional markers, blood pressure and body weight and composition. Also, the effect of diets on men's sleep, general wellbeing and satisfaction with treatment will be investigated. The proposed study can test a potentially effective nutritional intervention which is feasible to adopt and sustainable (in line with recent planetary diet recommendations). Confirming its effectiveness can fill the research gap, providing new knowledge and approach to the prevention and treatment of metabolic abnormalities in young, lean men.

Habitual diet - healthy eating guidelines provided for ethical reasons, no restrictions on the time of eating

Flexitarian diet (FD) will be based on planetary diet recommendations (predominantly plants; pulses and legumes as protein sources, meat and poultry consumed occasionally). Ways to facilitate this diet will be presented in the booklet prepared for them by the PI and a dietitian.

Time restricted eating (TRE) with 6 hour eating window - start and end hour to be an individual choice (some may prefer to consume their meals within an early window, e.g. 10am-4pm, some may prefer to consume their meals later in the day, e.g. 12:00-6pm). However, participants will be asked to be fairly consistent with their choice of their timing of eating hours. During fasting only water will be permitted;

Depending on the allocation arm, participants will be advised to follow a particular dietary plan (either flexitarian eating, time-restricted eating or both combined).

Change in fasting glucose concentration [mg/dL]. Blood samples will be collected after the overnight fast and the analysis will be performed on the Cobas Integra 400 plus analyzer.

The blood serum concentration of total cholesterol (in mmol/L). Blood samples will be collected after the overnight fast and the analysis will be performed on the Cobas Integra 400 plus analyzer.

The blood serum concentration of high-density lipoprotein cholesterol (in mmol/L). Blood samples will be collected after the overnight fast and the analysis will be performed on the Cobas Integra 400 plus analyzer.

The blood serum concentration of low-density lipoprotein cholesterol (in mmol/L). Blood samples will be collected after the overnight fast and the analysis will be performed on Cobas Integra 400 plus analyzer.

The concentration of serum triglycerides (in mmol/L). Blood samples will be collected after the overnight fast and the analysis will be performed on Cobas Integra 400 plus analyzer.

The measured values of body height and weight will be used for the calculation of body mass index (in kg/m^2).

The waist-to-hip ratio will be calculated from the measured values of waist and hip circumferences: waist circumference (cm) / hip circumference (cm).

Determination of abdominal fat volume will be measured in litres and performed using SECA® mBCA 515 analyser

The assessment of blood pressure (in mmHg) will be performed prior to and immediately after the intervention using electronic monitor (Omron M3 Intellisense Automatic Blood Monitor, Omron Healthcare, Mannheim, Germany).

Oxygen consumption (VO2) measured using ergospirometer CORTEX MetaMax 3b (ml oxygen/kg of body weight/minute). VO2 max is the maximum amount of oxygen the body can utilize during exercise.

Inclusion Criteria: Males Age 18-40 years Normal body weight At least one of metabolic abnormalities (elevated fasting glucose level - but not diabetes, elevated blood lipids, elevated blood pressure) Exclusion Criteria: Females Age <18 and >40 years Overweight or obesity (BMI>25 kg/m2) WC > 94cm Alcohol >14 units/week Smoking On medication Diabetes or other chronic diseases Vegetarians or vegans Don't own or unable to use a Smartphone with Apple iOS or Android OS