Resting metabolic rate (RMR) is the amount of energy the body uses at rest, and accounts for 60%-70% of daily energy expenditure. Although measured at rest, RMR is strongly influenced by physical activity because the increased metabolic rate during exercise is partially carried over even when exercise stops. Therefore, persons who are physically active maintain higher RMR and less body fat than do sedentary controls. It is well known that high energy intake stimulates whereas caloric restriction reduces RMR. Food thermogenesis corresponds to approximately 10% of daily energy expenditure. Diet-induced thermogenesis is greater on a high protein and carbohydrate diet than on a fat diet. Other factors the affect RMR are age (RMR tends to decline progressively over the life span) and body composition (lean body mass is regarded as the main determinant of RMR). However, the research regarding the effect of a specific combination of macronutrients and exercise on RMR is scarce.

Therefore, the aim of the current study is to assess the combined effect of a meal composition and physical activity on RMR in normal weight and overweight children, adolescents and adults.

One hundred (100) healthy volunteers, 50 normal weight (NW) and 50 overweight (OW), age 6-30 will be recruited for the current study. All participants and/or their parents will sign informed consent prior to their participation. Participants will visit the clinic 4 times, with a week's difference between them. Participants will arrive at the clinic after 12 hours of fasting and avoiding physical activity for 14 hours. During the first visit, their RMR will be measured, and 15min later they will perform 60 min of aerobic training, and 15 minutes later they will be asked to drink 300ml of water, followed by a second RMR test. In the consecutive visits they will follow the same routine without the first RMR test, and drink either carbohydrate enriched shake, protein enriched shake or fat enriched shake; in a random order.

Inclusion Criteria:

• Ages 6-30 years.
• Normal weight and over weight participants

Exclusion Criteria:

• Elite athletes
• Participants with physical limitations concerning strenuous physical activity.