Fat oxidation at rest predicts peak fat oxidation during exercise and metabolic phenotype in overweight men.
OBJECTIVE
To elucidate if fat oxidation at rest predicts peak fat oxidation during exercise and/or metabolic phenotype in moderately overweight, sedentary men.


METHODS
Cross-sectional study.


METHODS
We measured respiratory exchange ratio (RER) at rest in 44 moderately overweight, normotensive and normoglycemic men and selected 8 subjects with a low RER (L-RER, body mass index (BMI): 27.9+/-0.9 kg m(-2), RER: 0.76+/-0.02) and 8 with a high RER (H-RER; BMI 28.1+/-1.1 kg m(-2), RER: 0.89+/-0.02). After an overnight fast, a venous blood sample was obtained and a graded exercise test was performed. Fat oxidation during exercise was quantified using indirect calorimetry.


RESULTS
Peak fat oxidation during exercise was higher in L-RER than in H-RER (0.333+/-0.096 vs 0.169+/-0.028 g min(-1); P<0.01) and occurred at a higher relative intensity (36.2+/-6.6 vs 28.2+/-3.1% VO(2max), P<0.05). Using the International Diabetes Federation criteria, we found that there was a lower accumulation of metabolic risk factors in L-RER than in H-RER (1.6 vs 3.5, P=0.028), and no subjects in L-RER and four of eight subjects in H-RER had the metabolic syndrome. Resting RER was positively correlated with plasma triglycerides (P<0.01) and negatively with plasma free fatty acids (P<0.05), and peak fat oxidation during exercise was positively correlated with plasma free fatty acid concentration at rest (P<0.05).


CONCLUSIONS
A low RER at rest predicts a high peak fat oxidation during exercise and a healthy metabolic phenotype in moderately overweight, sedentary men.
Rosenkilde
M
M
Department of Biomedical Sciences, Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.
Nordby
P
P
Nielsen
L B
LB
Stallknecht
B M
BM
Helge
J W
JW
D000328:Adult; D001481:Basal Metabolism / Q000502:physiology*; D015992:Body Mass Index; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology; D005215:Fasting / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006801:Humans; D050356:Lipid Metabolism / Q000235:genetics / Q000502:physiology*; D008297:Male; D050177:Overweight / Q000378:metabolism / Q000503:physiopathology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D012146:Rest / Q000502:physiology; D057185:Sedentary Behavior; D014280:Triglycerides / Q000097:blood
D005230:Fatty Acids, Nonesterified; D014280:Triglycerides