Table 3: Concentrations of Major Fuels During Starvation in Man
Substance 

Serum or plasma concentration (mM) 

 Days

Fed 1 2 3 4 5 6 7  28-42
Glucose 5.5 4.7 4.1 3.8 3.6 3.6 3.5 3.5  3.6
 Fatty acids 0.30 0.42 0.82 1.04 1.15 1.27 1.18 1.88  1.44
 Ketone bodies 0.01 0.03 0.55 2.15 2.89 3.64 3.98 5.34  7.32
Insulin* >40 15.2 9.2 8.0 7.7 8.6 7.7 8.3  6

 *Insulin concentration is expressed in mU/mL

Data from E. A. Newsholme & A. R. Leach (1983) Biochemistry for the Medical Sciences, John Wiley, NY. pp 338 & 539.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Redrawn from R.W. McGilvery (1979) Biochemistry: A Functional Approach. W. B. Saunders Company, Philadelphia: p 704

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fuel Utilization in Prolonged Exercise

 

Fuel O2 utilization

 

Fuel Concentrations in Blood (mM)

  Blood-delivered Fuels
Exercise Time (min) Muscle Glycogen Glucose Fatty Acid Glucose Lactate Fatty Acid Glycerol
0       4.5 1.1 0.66 0.04
40 36% 27% 37% 4.6 1.3 0.78 0.19
90 22% 41% 37%        
180 14% 36% 50% 3.5 1.4 1.57 0.39
240 8% 30% 62% 3.1 1.8 1.83 0.48
Data from E. A. Newsholme & A. R. Leach (1983) Biochemistry for the Medical Sciences, John Wiley, NY. pp 370-372.

 

Plot of human fuel usage vs. exercise intensity as % maximum oxygen use

 

 

Last modified 6 May 2013