The researcher will enrol eligible participants by means of an advertisement leaflet and word of mouth in the campus of the University of Glasgow and other major public areas. Those who show interest about the study will be contacted by the researcher who will explain the study in detail and will give them a copy of the participant information leaflet. If the participant is happy to participate, he will sign an informed consent form and privacy notes. Only participants with stable body weight for at least 3 months will be recruited and we will exclude those who are on positive or negative energy balance (recent weight gain or loss, ±2 kg the past month).
As part of the screening process, each participant will be asked to fill in Physical Activity Readiness Questionnaire (PARQ) and Health Screening Questionnaire. Only those who answered "no" to all questions in PARQ and were in generally good health will carry on with other aspects of the study. These questionnaires will be completed during screening session, which will take place at NLB, GRI. Height and body weigh will be measured at the screening session. Only those with BMI between 25.0-30 kg/m2 will be invited to participate. Smokers will not be recruited. It will be explained that their participation is voluntary, that they may withdraw at any point if they wish, and that the data collected will be anonymised. We will thank those subjects who have expressed an interest about the study but do not qualify and we will explain to them why they need to be excluded. Those who are eligible to participate will be enrolled in the trial which will last for 4 weeks and we will measure their height and weight.
Main Experimental Trials:
The experimental trials will last over 2 days. On day 1 Participants will consume provided dinner and on Day2 attend the metabolic research unit at New Lister Building of the Royal Infirmary in the fasted state at approximately 09:00 am. An intravenous cannula will be placed by a trained phlebotomist upon arrival. This will be used to draw blood samples throughout trial. After the collection of the first blood sample, the participant will walk on the treadmill at speed and grade corresponding to 55% of their maximal oxygen consumption. During exercise, participants will be wearing a heart rate monitor and a face mask connected to indirect calorimetry equipment to allow measurements of fat and CHO oxidation Ratings of perceived exertion will be recorded at every 10 minutes. Following exercise, participants will rest for 60 minutes and then either high CHO or high fat morning meal will be provided. Further blood samples will be collected for the duration of 5-hours; in total no more than 70 ml of blood will be taken during each of the trials. Following the last blood sample collection, participants will eat from ad libitum buffet and then leave laboratory and during the rest of the day will be recording all food and drink consumed.
Meal On day 1 dinner meal will provided with either high carbohydrate or high fat meal which contains 35% of participants total daily energy intakes. In high CHO trial, meal will consist of pasta, meat ball and orange juice. In high fat trial, meals will be based on burger, cheese, mushroom, nuts, and butter. On the day 2 and after 60 minutes exercise, participants will consume morning meal, providing 30% of their total daily energy intake. In high fat trial, morning meals will be based on white bread, peanut butter, nuts, and olives. In high CHO trial, meal will consist of oats, skimmed milk, banana and seedless raisins.
Exercise Tests Participants will conduct a submaximal exercise test to estimate their maximal oxygen consumption (V̇O2 max), a marker of cardiorespiratory fitness. During the main experimental trials, participants will undergo a 60-minute walking exercise at a predetermined work rate corresponding to 55% of their predicted V̇O2 max. Both exercise sessions will be conducted on a treadmill and will be at intensity below 85% of maximal HR. Heart rate and ratings of perceived exertion will be recorded throughout the test via a heart rate monitor.
Preparation for experimental trials Participants will be asked to record dietary intake for 2 days prior to the first experimental trial and will be asked to replicate this in the 2 days prior to the second experimental trial. Prior to both experimental trials participants will be asked to avoid consumption of coffee and alcohol for the duration of 3 days.
