Modelling the associations between fat-free mass, resting metabolic rate and energy intake in the context of total energy balance.
BACKGROUND
The relationship between body composition, energy expenditure and ad libitum energy intake (EI) has rarely been examined under conditions that allow any interplay between these variables to be disclosed.


OBJECTIVE
The present study examined the relationships between body composition, energy expenditure and EI under controlled laboratory conditions in which the energy density and macronutrient content of the diet varied freely as a function of food choice.


METHODS
Fifty-nine subjects (30 men: mean body mass index=26.7±4.0 kg m(-2); 29 women: mean body mass index=25.4±3.5 kg m(-)(2)) completed a 14-day stay in a residential feeding behaviour suite. During days 1 and 2, subjects consumed a fixed diet designed to maintain energy balance. On days 3-14, food intake was covertly measured in subjects who had ad libitum access to a wide variety of foods typical of their normal diets. Resting metabolic rate (RMR; respiratory exchange), total daily energy expenditure (doubly labelled water) and body composition (total body water estimated from deuterium dilution) were measured on days 3-14.


RESULTS
Hierarchical multiple regression indicated that after controlling for age and sex, both fat-free mass (FFM; P<0.001) and RMR (P<0.001) predicted daily EI. However, a mediation model using path analysis indicated that the effect of FFM (and fat mass) on EI was fully mediated by RMR (P<0.001).


CONCLUSIONS
These data indicate that RMR is a strong determinant of EI under controlled laboratory conditions where food choice is allowed to freely vary and subjects are close to energy balance. Therefore, the conventional adipocentric model of appetite control should be revised to reflect the influence of RMR.
Academy of Sport and Physical Activity, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, UK.|Institute of Psychological Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
M
M
Hopkins
Institute of Psychological Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
G
G
Finlayson
Cognitive and Behavioural Centre for Research and Intervention, University of Coimbra, Coimbra, Portugal.
C
C
Duarte
Public Health Nutrition Research Group, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK.
S
http://orcid.org/0000-0002-0120-6890
S
Whybrow
UMR Inserm 1027, Université Paul Sabatier, CHU de Toulouse, France.
P
P
Ritz
Biomathematics and Statistics Scotland, Aberdeen, UK.
G W
GW
Horgan
Institute of Psychological Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
J E
JE
Blundell
College of Life and Natural Sciences, University of Derby, Derby, UK.
R J
RJ
Stubbs
D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001069:Appetite Regulation; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D004032:Diet; D004435:Eating / Q000502:physiology*; D002149:Energy Intake; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D012606:Scotland / Q000453:epidemiology