The effect of activity on insulin sensitivity and lipid metabolim in sedentary people.

Inactivity or the lack of physical activity have many negative effects on
several diseases, and could even cause diseases related to decreased energy
expenditure. Nowadays, the importance of physical activity and exercise are
emphasized in the literature and media. However, research recently published
shows that activities associated with everyday activities such as working in
and around the house, standing and walking, have a much greater role in energy
expenditure than exercise. These everyday activities are summarized as Non
Exercise Activity Thermogenesis (NEAT).

The effect of NEAT or inactivity on insulin sensitivity and lipid metabolism is
unclear. The objective of the present study is to evaluate the effect of 4 days
of mainly sitting, or sitting and walking, or sitting, walking and biking on
glucose and insulin concentrations in healthy volunteers. Literature shows that
4 days of inactivity is sufficient to see changes in glucose metabolism.

Intervention

The volunteers will follow 3 times a certain activity program for 4 days. These
activity programs are:
- Sitting: 14 hours sitting, 2 hours of everyday activities (standing and
walking), 8 hours of sleeping or laying down per day.
- Walking: 4 hours waking with normal speed, 8 hours sitting, 2 hour standing,
2 hours of everyday activities (standing and walking), 8 hours of sleeping or
laying down per day.
- Sitting/sporting: 13 hours sitting, 1 hour biking, 2 hours of everyday
activities (standing and walking), 8 hours of sleeping or laying down per day.
The volunteers will wear two accelerometers during these days, so we can
measure their activities more accurate. The CSA Actigraph accelerometer will be
placed on the back, and the ActivPAL on the leg. The volunteers will be
requested to take off the CSA Actigraph in the shower and during sleeping,
this is not the case for the ActivPAL. The volunteers will also be requested to
note their activities and thier diet in a diary.
After every 4 days of the activity program, an oral glucose tolerance test will
be performed in the moring of the next day (day 5). Before and 15, 30, 45, 60,
90, and 120 minutes after the ingestion of 75 gram of glucose in water, blood
will be drawn for measurements of glucose and insulin. Only at baseline, blood
will be drawn to measure cholesterol, HDL, LDL, triglycerides, apoB and apoA.
These blood draws will be done using a small catheter inserted into the
antecubital vein. In total, 73 mL of blood will be drawn with each OGTT. The
OGTT will be done 3 times. At the same day, height, weight and circumference
will be measured.

The oral glucose tolerance test will be performed 3 times. There is a small
risk of getting a bruise after the catheter insertion, fainting and vomiting.
Biking: at 4 days, subjects will be biking 2 x 30 min. This can possibly cause
muscle pain and fatigue during 1-2 days.