Fat oxidation before and after a high fat load in the obese insulin-resistant state.
BACKGROUND
Obesity may be associated with a lowered use of fat as a fuel, which may contribute to the enlarged adipose tissue stores.


OBJECTIVE
The aim of the present study was to study fatty acid use in the fasting state and in response to a high fat load in a large cohort of obese subjects (n = 701) and a lean reference group (n = 113).


METHODS
Subjects from eight European centers underwent a test meal challenge containing 95 en% fat [energy content 50% of estimated resting energy expenditure (EE)]. Fasting and postprandial fat oxidation and circulating metabolites and hormones were determined over a 3-h period.


RESULTS
Postprandial fat oxidation (as percent of postprandial EE, adjusted for fat mass, age, gender, center, and energy content of the meal) decreased with increasing body mass index (BMI) category (P < 0.01), an effect present only in those obese subjects with a relatively low fasting fat oxidation (below median, interaction BMI category x fasting fat oxidation, P < 0.001). Fasting fat oxidation increased with increasing BMI category (P < 0.001), which was normalized after adjustment for fat-free mass and fat mass. Furthermore, insulin resistance was positively associated with postprandial fat oxidation (P < 0.05) and negatively associated with fasting fat oxidation (expressed as percent of EE), independent of body composition.


CONCLUSIONS
The present data indicate an impaired capacity to regulate fat oxidation in the obese insulin-resistant state, which is hypothesized to play a role in the etiology of both obesity and insulin resistance.
Blaak
Ellen E
EE
Department of Human Biology, Nutrition Research Centre, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands. e.blaak@hb.unimaas.nl
Hul
Gabby
G
Verdich
Camilla
C
Stich
Vladimir
V
Martinez
Alfredo
A
Petersen
Martin
M
Feskens
Edith F M
EF
Patel
Kishor
K
Oppert
Jean Michel
JM
Barbe
Pierre
P
Toubro
Søren
S
Anderson
Ingalena
I
Polak
Jan
J
Astrup
Arne
A
Macdonald
Ian A
IA
Langin
Dominique
D
Holst
Claus
C
Sørensen
Thorkild I
TI
Saris
Wim H M
WH
D000328:Adult; D019540:Area Under Curve; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight; D004041:Dietary Fats / Q000378:metabolism* / Q000494:pharmacology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D012727:Sex Characteristics
D004041:Dietary Fats; D020738:Leptin; D007334:Insulin-Like Growth Factor I; D006854:Hydrocortisone