Effect of a Protein Intake on Weight Loss of Overweight/Obese Adults

This study is designed as a 12-week, randomised, parallel study, focused on overweight/obese men and women between 20 and 65 years old. All participants attend the Nutrition Intervention Unit of the Center for Nutrition Research in the University of Navarra for the screening visit and 4 more times during the intervention (week 1, 4, 8 and 12 of study). Screening visit: evaluation of the inclusion criteria. Volunteers who meet the inclusion criteria are provided with a feces collection kit, urine collection kit, food frequency questionnaire, visual analogue scale and minnesota physical activity questionnaire. Moreover, they are randomly assigned to one of the two intervention groups: * Control group: healthy dietary recommendations. * Experimental group: healthy dietary recommendations + 2 protein rich bars/day Clinical investigation day 1 (week 1): The volunteer attend the Nutrition Intervention Unit in fasting condition. Each volunteer is asked to provide the fece and urine samples, and completed questionnaires provided in screening visit. Then, anthropometric, body composition, densitometry and blood pressure measurements are taken and the gastrointestinal symptoms questionnaire is completed. After that, volunteer is provided with healthy dietary recommendations only or dietary recommendations and protein rich bars, depending on the allocated intervention group. Moreover, volunteer is provided with visual analogue scale to be completed for the Clinical investigation day 2. Clinical investigation day 2 (week 4): The volunteer attend the Nutrition Intervention Unit. The volunteer is asked to provide the visual analogue scale. Then, gastrointestinal symptoms questionnaire is completed and the adherence to the study is assessed. Then, body weight and blood pressure are measured. Volunteer is provided with fece and urine collection kits, food frequency questionnaire, minnesota physical activity questionnaire and visual analogue scale, to be completed for the Clinical investigation day 3. Finally, volunteers allocated in experimental group are provided with protein rich bars. Clinical investigation day 3 (week 8): The volunteer attend the Nutrition Intervention Unit in fasting condition. Each volunteer is asked to provide the fece and urine samples, and completed questionnaires provided in Clinical investigation day 2. After that, the adherence to the study is assessed. Then, anthropometric, body composition, densitometry and blood pressure measurements are taken and the gastrointestinal symptoms questionnaire is completed. Volunteer is provided with fece and urine collection kits, as well as food frequency questionnaire, minnesota physical activity questionnaire and visual analogue scale to be completed for the Clinical investigation day 4. Finally, volunteers allocated in experimental group are provided with protein rich bars. Clinical investigation day 4 (week 12): The volunteer attend the Nutrition Intervention Unit in fasting condition. Each volunteer is asked to provide the fece and urine samples, and completed questionnaires provided in Clinical investigation day 3. After that, the adherence to the study is assessed. Then, anthropometric, body composition, densitometry and blood pressure measurements are taken and the gastrointestinal symptoms questionnaire is completed.