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

Obesity is considered the epidemic of the 21st century. Obesity is a multifactorial disease and the most important risk factors are poor diet and sedentary lifestyle. An excessive body weight contributes to increase the risk of suffering from other diseases and mortality rates. Therefore, the prevention and control of excessive body weight as well as its comorbidities are essential. In this sense, the principal strategy to treat obesity is to improve dietary habits and increase physical activity. However, the rate of obesity continues rising. In order to deal with this problem, new strategies to combat obesity are being investigated, such as the investigation of new bioactive compounds with satiating capacity that can be included in healthy dietary patterns to improve adherence to dietary treatments.

Considering this background, the main objective of this research is to assess the effect of daily consumption of protein rich bars accompanied by healthy dietary recommendations on weight loss of overweight/obese adult men and women.

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.

Eligibility Criteria:
Inclusion Criteria:

* Volunteers with BMI between 24.9 and 34.9 kg/m2.
* Physical examination and vital signs normal or clinically irrelevant to the study.
* Volunteers undergoing pharmacological treatment will be included if the dose is stable for at least 3 months before the start of the study, excluding treatments that alter gastrointestinal function and antidiabetics.
* Subjects must be able to understand and be willing to sign the informed consent, as well as comply with all the procedures and requirements of the study.
* Present a stable weight (+/-3kg) in the last three months before the start of the study.

Exclusion Criteria:

* Subjects with relevant functional or structural abnormalities of the digestive system, such as malformations, angiodysplasias, active peptic ulcers, chronic inflammatory or malabsorption diseases, hiatal hernia, reflux, etc.
* Subjects with a high alcohol intake, more than 14 units (women) and 20 units (men).
* Women who are breastfeeding or pregnant.
* Subjects who have undergone surgical interventions with permanent sequelae in the digestive system (for example, gastroduodenostomy).
* Subjects with liver disease.
* Subjects with some type of cancer or undergoing treatment for it, or who have not had a period of at least 5 years since its eradication.
* Subjects with allergies to any component of the product under study or any other food that interferes and makes it difficult to monitor the study.
* Subjects who present some type of cognitive and/or psychic impairment.
* Subjects in whom poor collaboration is expected or who, in the opinion of the investigator, have difficulties in following the study procedures.
* Subjects who work night shifts.
* Subjects who follow some type of supplementation that interferes with the study.
* Subjects who are immersed in some treatment for weight loss.