Regulation of energy balance during long-term physical inactivity induced by bed rest with and without exercise training.
BACKGROUND
Short-term physical inactivity affects energy balance and is considered conducive to weigh gain. Long-term effects are unknown.


OBJECTIVE
The objective of the study was to use a bed-rest model to determine the long-term effects of physical inactivity on energy balance regulation and test the effect of exercise training on energy balance adjustment to physical inactivity.


METHODS
Sixteen lean women were divided into two groups (n = 8 each): a control group subjected to a strict 60-d bed rest and an exercise group subjected to a combined aerobic/resistive exercise training concomitantly to bed rest. Body composition, spontaneous energy intake, hunger, total energy expenditure (TEE), and fasting gut hormones were measured.


RESULTS
Based on bed-rest-induced body composition changes, the control group were in slight negative energy balance (-0.4 +/- 0.4 MJ/d; P = 0.01 vs. zero), essentially due to muscle atrophy (P < 0.001 vs. zero). The stable fat mass (P = 0.19 vs. zero), and the matching between spontaneous energy intake and TEE indicated, however, a stable energy balance. Hunger and gut hormones remained unchanged during the bed rest. In the exercise group, TEE was 24% higher than in the control group (P = 0.004). Unexpectedly, desire to consume food (P = 0.025) decreased and spontaneous energy intake (P = NS) was not stimulated, promoting a negative energy balance (-1.1 +/- 0.5 MJ/d, P = 0.0003 vs. zero).


CONCLUSIONS
Energy balance is regulated during 2 months of physical inactivity, contrasting with short-term experiments. Conversely, exercise-induced energy expenditure in bed-resting subjects who have no spontaneous physical activity did not induce hunger and promoted a negative energy balance, suggesting a potential role of nonexercise physical activities in energy balance regulation.
Bergouignan
Audrey
A
Institut Pluridisciplinaire Hubert Curien, Département d'Ecologie, Physiologie, et Ethologie, Université de Strasbourg, Centre National de la Recherche Scientifique, 23 Rue Becquerel, 67087 Strasbourg, France.
Momken
Iman
I
Schoeller
Dale A
DA
Normand
Sylvie
S
Zahariev
Alexandre
A
Lescure
Bernadette
B
Simon
Chantal
C
Blanc
Stéphane
S
D000328:Adult; D000704:Analysis of Variance; D001510:Bed Rest; D001823:Body Composition / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology; D005260:Female; D054439:Ghrelin / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D006801:Humans; D006815:Hunger / Q000502:physiology; D020738:Leptin / Q000097:blood; D013995:Time; D013997:Time Factors
D054439:Ghrelin; D020738:Leptin; D052216:Glucagon-Like Peptide 1