Background: Protein intake is important for maintaining skeletal muscle mass. These proteins consist of a collection of small building blocks which are called amino acids. There are two types of amino acids that are needed to build muscle: essential amino acids (EAA) and non-essential amino acids (NEAA). EAAs cannot be made in the body and must be consumed through foods, while NEAAs can be made within the body. However, if NEAA are not consumed through foods, the process of making NEAA in the body costs the body energy. It is still unknown what the impact of a diet containing too few non-essential amino acids is for muscle building and the body's energy metabolism.

Objective: To determine if a diet lacking NEAA, with or without being replaced by additional EAA, influences muscle protein building and whole-body metabolism.

Study design: Randomized, parallel design, double-blind, 10-day dietary intervention study.

Study population: 45 healthy (BMI 22-30 kg/m2) young males (age: 18-35 y inclusive).

Hypothesis: It is hypothesized that a diet lacking NEAA, with or without being replaced by additional EAA, decreases muscle protein building in humans.

Inclusion Criteria:

• Male
• Age between 18 and 35 y inclusive
• BMI between 22 and 30 kg/m2
• Non-smoker
• Having given informed consent

Exclusion Criteria:

• Participating in a structured (progressive) exercise program
• Smoker
• Diagnosed GI tract disorders or diseases
• Diagnosed musculoskeletal disorders
• Diagnosed metabolic disorders (e.g. diabetes)
• Cardiovascular disease
• Hypertension (blood pressure above 140/90 mmHg)
• Donated blood 3 months prior to test day
• Use of any medications known to affect protein metabolism (i.e. corticosteroids, non-steroidal anti-inflammatories).
• Chronic use of gastric acid suppressing medication
• Chronic use of anti-coagulants
• Any intolerance to foods included in the standardized diet intervention
• Any implants that would be a contra-indication for performing an MRI scan