title: Increased nocturnal fat oxidation in young healthy men with low birth weight: results from 24-h whole-body respiratory chamber measurements.
abstract: OBJECTIVE
  Low birth weight (LBW), a marker of disturbed fetal growth, is associated with adiposity and increased risk of type 2 diabetes (T2D). The aim of the study was to investigate whether LBW is associated with changes in 24-h energy expenditure (EE) and/or substrate utilization rates, potentially contributing to the development of adiposity and/or T2D compared to matched control subjects.
  
  
  METHODS
  Forty-six young, healthy men were included in the study; 20 with LBW (≤ 10th percentile) and 26 control subjects with normal birth weight (NBW) (50th-90th percentile). The subjects were fed a weight maintenance diet and 24-h energy expenditure (EE), respiratory quotient (RQ), and substrate oxidation were assessed in a respiratory chamber.
  
  
  RESULTS
  No differences in 24-h EE, RQ or substrate oxidation were observed between LBW and controls. Interestingly, the LBW group exhibited lower nocturnal RQ compared to controls (0.81 ± 0.01 vs. 0.85 ± 0.01 (mean ± SE), P = 0.01), and hence higher nocturnal fat oxidation (2.55 ± 0.13 vs. 2.09 ± 0.12 kJ/min (mean ± SE), P = 0.02).
  
  
  CONCLUSIONS
  Young LBW men do not exhibit reductions in 24-h EE. However, LBW subjects display increased nocturnal fat oxidation at the expense of reduced glucose oxidation. We speculate that this may be associated with insufficient capability to retain fat in subcutaneous adipose tissue after meals during day time, with an increased rate of nocturnal and morning lipolysis, and potentially with subtle elevations of gluconeogenesis and of fasting glucose levels in the LBW subjects.
authors: Steno Diabetes Center, Gentofte, Denmark. charlotte.broens@regionh.dk
authors: C
authors: C
authors: Brøns
authors: S K
authors: SK
authors: Lilleøre
authors: C B
authors: CB
authors: Jensen
authors: S
authors: S
authors: Toubro
authors: A
authors: A
authors: Vaag
authors: A
authors: A
authors: Astrup
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology; D003718:Denmark; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight / Q000378:metabolism* / Q000502:physiology; D007231:Infant, Newborn; D050356:Lipid Metabolism / Q000502:physiology*; D008066:Lipolysis / Q000502:physiology; D008297:Male; D010084:Oxidation-Reduction; D012119:Respiration; D012129:Respiratory Function Tests; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology; D055815:Young Adult