Today, there is an important lack of knowledge on child metabolism and the effects of phytochemical-rich foods, which includes fruits and vegetables and plant-derived foods. Here, the investigators will monitor the metabolism of children using minimally invasive techniques at rest, and with physical/mental activities and assess the changes associated with the intake of cocoa-based food.

Inclusion Criteria:

All subjects must comply with all the following inclusion criteria:

• Healthy and physically active, and no diabetes or metabolism related disorders in their first degree relatives (as determined by medical and activity questionnaire)
• Caucasian, with English as a first language and an adequate standard of literacy.
• BMI adjusted for age and gender which falls between the 9th and 91st as shown in the Child Growth Foundation BMI growth charts
• 8-13 years of age
• Having obtained his/her informed assent
• Having obtained his/her legal representative's informed consent
• Willing to allow their family doctor (GP) to be informed about their participation in this study

Exclusion Criteria:

Subjects representing one or more of the following criteria are excluded from participation in the study.

• Post-pubertal
• Taking any medication
• Smoker
• Undergoing medical treatment or investigations
• Body mass index > 24
• Suffer from chronic diseases (with regular intake of drugs, medical history)
• Vegetarians
• Vaccination in the last 4 months
• Any know food allergies or intolerance
• Pregnancy
• Special diet or weight loss program (e.g. Atkins diet)
• Acute illness
• Fever, cold, flu
• Participation in a cholesterol management program with functional foods like food supplement enriched in omega-3 fatty acids, dairy products enriched with phytosterols (margarines, yoghurts).