Loss of body nitrogen on fasting

Am J Clin Nutr. 1979 Aug;32(8):1570-4. doi: 10.1093/ajcn/32.8.1570.


An analysis of the change in total body nitrogen during fasting shows that it declines exponentially, a small fraction being lost rapidly (t 1/2 of a few days), and the remainder being lost slowly (t 1/2 of many months). The obese faster loses N, and weight, at a slower relative rate than the nonobese; and the ratio of N loss to weight loss during an extended fast is inversely related to body fat content, being about 20 g/kg in the nonobese and about 10 g/kg in those with body fat burdens of 50 kg or more. The loss of body N on a low protein-calorie adequate diet can also be described in exponential terms, and this function allows an estimate to be made of the N requirement.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Body Weight
  • Dietary Proteins
  • Fasting*
  • Humans
  • Kinetics
  • Male
  • Middle Aged
  • Nitrogen / metabolism*
  • Obesity / metabolism*


  • Dietary Proteins
  • Nitrogen