EFFECT OF A PROTEIN-SPARING DIET AND BRIEF FAST ON NITROGEN-METABOLISM IN MILDLY OBESE SUBJECTS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 89  (5) , 1030-1035
Abstract
Five young, mildly obese females consumed a formula diet providing total calories at 1.2 .times. basal energy expenditure and egg white protein, 1.5 g/kg ideal body weight (IBW), for 1 wk (period 1). During period 2, lasting 3 wk, a protein-sparing modified fast (PSMF) consisted of similar amounts of egg white without nonprotein calories followed by a 1-wk total fast (period 3). In the final period (4), a PSMF with the use of meat protein, 1.5 g/kg IBW, alone was given for 1 wk. N balance (Nbal) measurements were made in all periods, and periods 2, 3 and 4 were compared with period 1. No significant difference existed between period 1 and period 2, although Nbal improved weekly during period 2. N excretion in period 3 was similar to that found after 3 wk of total fasting and was significantly negative, whereas positive balances occurred in period 4 with both periods being significantly different from period 1. N equilibrium in a PSMF can be achieved with the use of protein free from fat, confirming earlier experience with meat protein. The metabolic adaptation which occurs during total fasting and results in reduced N loss develops in the course of a PSMF. After a deficit in lean body mass is produced, net protein anabolism can be achieved by a PSMF despite insufficient dietary energy.

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