Measurements were conducted in two phases. All subjects were seen in single-sex pairs and stayed in a dedicated metabolic suite for 9 consecutive days. During phase 1 (days 1 to 3- choice experiment) they ate freely at each mealtime from menus comprising a combination of foods containing different percentages of energy as protein (PEP), set at 10%, 15% or 25% (26). During phase 2 (days 4 to 8), pairs were randomized to one of three groups each of which received only foods that contained 10%, 15% or 25% PEP. The participants were blinded to the treatment. Participants were taken for a 1-hour supervised walk each day at 4 pm.