Aim of the study is to investigate the effects of high-protein, ultraprocessed foods on the regulation of energy balance in a metabolic chamber. The primary outcome parameter of the study is the energy balance (ad libitum energy intake and energy expenditure).

Each of the two study weeks starts with a 3-day run-in period with controlled diet at home, following 48 hours in a metabolic chamber. On the day the participants leave the metabolic chamber, they keep a food record over the rest of the day at home.

1. week: meals containing 30 % protein (80 % ultraprocessed high-protein foods), physical activity level (PAL) 1.45, 2 intervention days in the metabolic chamber: ad libitum energy intake
2. week: meals containing 13 % protein (80 % ultraprocessed foods with moderate protein content), physical activity level (PAL) 1.45, 2 intervention days in the metabolic chamber: ad libitum energy intake

Inclusion Criteria:

• healthy
• BMI 19-29 kg/m2
• low-medium habitual physical activity
• women with regular menstrual cycle (during intervention in follicular phase)

Exclusion Criteria:

• smoking
• chronic illnesses (e.g. renal dysfunction)
• regular intake of medication
• food allergies / intolerances
• vegans and vegetarians
• regular high physical activity (exercise >1 hour/d)
• current weight loss diet / weight loss of >5 kg in the last 3 months
• pregnant / lactating women
• persons incapable of giving informed legal consent
• restraint eaters (according to the German version of the 'Three-Factor-Eating-Questionnaire', Stunkard und Messick (1985))