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.