Timing of Caloric Intake, Diet-induced Thermogenesis and Hormonal Pattern

Overview

The investigators aim at analyzing whether eating a standard meal in the evening (at 8:00 pm) determines in the same individuals a lower diet-induced thermogenesis (DIT) and a different hormonal response than the consumption of the same meal in the morning (at 8:00 am). The primary outcome is: the intra-individual variation in DIT after the evening and morning meal consumption. The secondary outcomes are the intra-individual variations in glucose, triglyceride, insulin, free fatty acids, leptin, glucagon-like peptide-1, acylated ghrelin, adrenalin, noradrenalin, after the evening and morning meal consumption.

Twenty healthy volunteers (ten males and ten females) are recruited among students and graduates attending the Department of Medical Sciences of Turin (Italy) to take part to this randomized cross-over trial. Participants randomly receive first the standard meal at 8:00 am and the week after the standard meal at 8:00 pm or vice versa. Eight-h before the meal (respectively at 12:00 pm or at 12:00 am), the participants receive the same standard meal (without protein supplementation) at their home, and then are asked to spend in bed the following 6 hours. A 24-h urine collection is collected the day before each test in order to determine total urinary nitrogen excretion. The standard meal consists of: 100g white bread, 100g ham, 50g cheese, 125g yogurt, 200ml fruit juice, plus 25g protein supplement. The participants must consume each meal in 25-30 minutes. A 30-min basal calorimetric (Deltatrac II) exam is performed. Participants remain in a supine position but awake and motionless on a hospital bed during the whole period, except during the meal, when they can sit to eat. At 8:00 am (or pm), the participants consume the meal, and then rest in a supine position for 90 min. Then, a second 60 min-calorimetric evaluation is done. From the first calorimetric exam (the basal) until the end of the second (post-prandial) blood samples are drawn every 30 min. The same time schedule is adopted in the case of the morning meal (at 8:00 am) and the evening meal (at 8:00 pm). The random sequence (morning/evening, evening/morning meal) is computer-generated, using blocks of different lengths in random order. The following are measured: weight, height, waist circumference, and at baseline and every 30-min during the morning and evening tests: glucose, triglyceride, insulin, free-fatty acids, leptin, glucagon-like peptide-1, acylated ghrelin, adrenalin, noradrenalin.