High altitude simulation and weight management

An unintended loss of body weight is not uncommon for mountaineers and for
people otherwise exposed to high altitude conditions (thin air) for a longer
period of time. COPD patients may experience similar effects because of their
respiratory problems. The nature of the weight loss is not always clear and is
supposed to be multifactorial. A reduction in body weight can be caused by a
loss of body water, body fat or lean body mass (protein). The size of the
weight loss seems to be related to the level and the duration of the high
altitude exposure, to the level of physical activity at altitude as well as to
the individual tolerance to high altitude conditions. Dehydration, reduced
appetite, a change in metabolic substrates and an increase in energy
expenditure have been suggested as potential mechanisms for weight loss under
high altitude conditions. The evidence for high altitude weight loss suggests
that exercise programmes for weight management could benefit from high altitude
simulation at sea level. An innovative approach of exercise programmes that
make use of high altitude simulation to increase energy expenditure provides in
our view the best perspective voor weight management. An acute increase in
energy expenditure, in response to high altitude simulation, has to be expected
when lactate, produced as residual product of anaerobic glycolysis,is cleared
by gluconeogenesis. It is well known that energy expenditure of the body
increases upon an increase in the level of gluconeogenesis.

The primary objective is to show that energy expenditure of the body, during
moderate physical activity on a bike ergometer, can become higher in response
to high altitude simulation. The secondary objetive is to show that an increase
in energy expenditure can be linked to the clearance of lactate produced under
high altitude simulation as by product of as anaerobic glycolyis.

The study has a 'Randomised controlled single blind cross-over design'

The study consists of a exercise protocol of 30 min. This exercise protocol is
executed twice, once under sea level conditions and once under high altitude
simulation (2000 m). For each individual the level of exercise is predetermined
by means of a LSSH (Lactate steady State - Hypoxia) screening protocol.

In order to participate in the study subjects have to fill in a questionairre
and will be subjected to a sport medical screening (a.o. ECG at max work load,
long function test). Based on this information obtained the sports physician
decides about in- or exclusion of the subjects. A LSSH (Lactate Steady State -
Hypoxia) screening is used to determine the highest word load (stages of 15
Watt) under which the subject is able to maintain a constant lactate level
under high altitude simulation. The exercise protocols will be performed under
sea level conditions and under high altitude simulation condition at a work
load 3 stages (= 45 Watt) lower. During the exercise protocols oxygen
consumption will be measured by indirect calorimetry (ventilated hood). During
the LSSH screening and the exercise protocols subjects have to behave s quite
as possible (no talking etc). On the morning of the sport medical screening,
the LSSH screening and the exercise sessions subjects have to come to the test
facilcity (HAN - SENECA) in an overnight fasting condition. During the LSSH
screening and the exercise session at max 12 small blood samples are taken from
the middle finger. At certain time intervals subjects are asked about their
'Rate of Perceived Exertion' (RPE).