The effect of rate and extent of weight loss on urea salvage in obese male subjects

Peter Faber, Alexandra Johnstone, Eileen R Gibney, Marinos Elia, R James Stubbs, Paula L Roger, Eric Milne, William Buchan, Gerald Lobley

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

It is well established that in human subjects a proportion of urea production undergoes hydrolysis in the gastrointestinal tract with release of N potentially available for amino acid synthesis. Previous studies have suggested adaptive changes in urea kinetics, with more urea-N retained within the metabolic pool during reduced dietary intakes of energy and protein. We therefore investigated the effect of rate and extent of weight loss on adaptive changes in urea kinetics in two groups (each n 6) of obese men (mean age 43 (So 12) years, BMI 34.8 (SD 2.9) kg/m(2)) during either total starvation for 6 d or a very-low-energy diet (2.55 MJ/d) for 21 d. Subjects were resident in the Human Nutrition Unit of the Rowett Research Institute (Aberdeen, Scotland, UK) and lost 6 and 9% initial body weight within the starvation and dieting groups respectively. Changes in urea-N metabolism were assessed by stable isotope tracer kinetics using [N-15 N-15]urea infused intravenously for 36 h before, during and after weight loss. In response to weight loss, urea production decreased (P< 0.01) by 25% from 278 to 206 &mu;mol urea-N/h per kg within the dieting group only. However, no changes were observed in the proportion of urea being hydrolysed in the gastrointestinal tract (range 20-25%) or in the proportion of N retained for anabolic purposes (80-85% urea-N from gastrointestinal hydrolysis) within either group. It was concluded that no adaptive changes in urea kinetics occurred in response to either the different rate or extent of weight loss.

Original languageEnglish
Pages (from-to)221-231
Number of pages11
JournalBritish Journal of Nutrition
Volume90
Issue number1
DOIs
Publication statusPublished - 1 Jul 2003

Keywords

  • Adaptation, Physiological
  • Adult
  • Diet, Reducing
  • Energy Metabolism
  • Humans
  • Male
  • Middle Aged
  • Nitrogen
  • Nitrogen Isotopes
  • Obesity
  • Starvation
  • Urea
  • Weight Loss
  • Urea kinetics
  • Body-composition
  • Nitrogen losses
  • Amino-acids
  • Normal men
  • Protein
  • Metabolism
  • Kinetics
  • N-15
  • Fat

Cite this

The effect of rate and extent of weight loss on urea salvage in obese male subjects. / Faber, Peter; Johnstone, Alexandra; Gibney, Eileen R; Elia, Marinos; Stubbs, R James; Roger, Paula L; Milne, Eric; Buchan, William; Lobley, Gerald.

In: British Journal of Nutrition, Vol. 90, No. 1, 01.07.2003, p. 221-231.

Research output: Contribution to journalArticle

Faber, P, Johnstone, A, Gibney, ER, Elia, M, Stubbs, RJ, Roger, PL, Milne, E, Buchan, W & Lobley, G 2003, 'The effect of rate and extent of weight loss on urea salvage in obese male subjects', British Journal of Nutrition, vol. 90, no. 1, pp. 221-231. https://doi.org/10.1079/BJN2003859
Faber, Peter ; Johnstone, Alexandra ; Gibney, Eileen R ; Elia, Marinos ; Stubbs, R James ; Roger, Paula L ; Milne, Eric ; Buchan, William ; Lobley, Gerald. / The effect of rate and extent of weight loss on urea salvage in obese male subjects. In: British Journal of Nutrition. 2003 ; Vol. 90, No. 1. pp. 221-231.
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abstract = "It is well established that in human subjects a proportion of urea production undergoes hydrolysis in the gastrointestinal tract with release of N potentially available for amino acid synthesis. Previous studies have suggested adaptive changes in urea kinetics, with more urea-N retained within the metabolic pool during reduced dietary intakes of energy and protein. We therefore investigated the effect of rate and extent of weight loss on adaptive changes in urea kinetics in two groups (each n 6) of obese men (mean age 43 (So 12) years, BMI 34.8 (SD 2.9) kg/m(2)) during either total starvation for 6 d or a very-low-energy diet (2.55 MJ/d) for 21 d. Subjects were resident in the Human Nutrition Unit of the Rowett Research Institute (Aberdeen, Scotland, UK) and lost 6 and 9{\%} initial body weight within the starvation and dieting groups respectively. Changes in urea-N metabolism were assessed by stable isotope tracer kinetics using [N-15 N-15]urea infused intravenously for 36 h before, during and after weight loss. In response to weight loss, urea production decreased (P< 0.01) by 25{\%} from 278 to 206 &mu;mol urea-N/h per kg within the dieting group only. However, no changes were observed in the proportion of urea being hydrolysed in the gastrointestinal tract (range 20-25{\%}) or in the proportion of N retained for anabolic purposes (80-85{\%} urea-N from gastrointestinal hydrolysis) within either group. It was concluded that no adaptive changes in urea kinetics occurred in response to either the different rate or extent of weight loss.",
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T1 - The effect of rate and extent of weight loss on urea salvage in obese male subjects

AU - Faber, Peter

AU - Johnstone, Alexandra

AU - Gibney, Eileen R

AU - Elia, Marinos

AU - Stubbs, R James

AU - Roger, Paula L

AU - Milne, Eric

AU - Buchan, William

AU - Lobley, Gerald

PY - 2003/7/1

Y1 - 2003/7/1

N2 - It is well established that in human subjects a proportion of urea production undergoes hydrolysis in the gastrointestinal tract with release of N potentially available for amino acid synthesis. Previous studies have suggested adaptive changes in urea kinetics, with more urea-N retained within the metabolic pool during reduced dietary intakes of energy and protein. We therefore investigated the effect of rate and extent of weight loss on adaptive changes in urea kinetics in two groups (each n 6) of obese men (mean age 43 (So 12) years, BMI 34.8 (SD 2.9) kg/m(2)) during either total starvation for 6 d or a very-low-energy diet (2.55 MJ/d) for 21 d. Subjects were resident in the Human Nutrition Unit of the Rowett Research Institute (Aberdeen, Scotland, UK) and lost 6 and 9% initial body weight within the starvation and dieting groups respectively. Changes in urea-N metabolism were assessed by stable isotope tracer kinetics using [N-15 N-15]urea infused intravenously for 36 h before, during and after weight loss. In response to weight loss, urea production decreased (P< 0.01) by 25% from 278 to 206 &mu;mol urea-N/h per kg within the dieting group only. However, no changes were observed in the proportion of urea being hydrolysed in the gastrointestinal tract (range 20-25%) or in the proportion of N retained for anabolic purposes (80-85% urea-N from gastrointestinal hydrolysis) within either group. It was concluded that no adaptive changes in urea kinetics occurred in response to either the different rate or extent of weight loss.

AB - It is well established that in human subjects a proportion of urea production undergoes hydrolysis in the gastrointestinal tract with release of N potentially available for amino acid synthesis. Previous studies have suggested adaptive changes in urea kinetics, with more urea-N retained within the metabolic pool during reduced dietary intakes of energy and protein. We therefore investigated the effect of rate and extent of weight loss on adaptive changes in urea kinetics in two groups (each n 6) of obese men (mean age 43 (So 12) years, BMI 34.8 (SD 2.9) kg/m(2)) during either total starvation for 6 d or a very-low-energy diet (2.55 MJ/d) for 21 d. Subjects were resident in the Human Nutrition Unit of the Rowett Research Institute (Aberdeen, Scotland, UK) and lost 6 and 9% initial body weight within the starvation and dieting groups respectively. Changes in urea-N metabolism were assessed by stable isotope tracer kinetics using [N-15 N-15]urea infused intravenously for 36 h before, during and after weight loss. In response to weight loss, urea production decreased (P< 0.01) by 25% from 278 to 206 &mu;mol urea-N/h per kg within the dieting group only. However, no changes were observed in the proportion of urea being hydrolysed in the gastrointestinal tract (range 20-25%) or in the proportion of N retained for anabolic purposes (80-85% urea-N from gastrointestinal hydrolysis) within either group. It was concluded that no adaptive changes in urea kinetics occurred in response to either the different rate or extent of weight loss.

KW - Adaptation, Physiological

KW - Adult

KW - Diet, Reducing

KW - Energy Metabolism

KW - Humans

KW - Male

KW - Middle Aged

KW - Nitrogen

KW - Nitrogen Isotopes

KW - Obesity

KW - Starvation

KW - Urea

KW - Weight Loss

KW - Urea kinetics

KW - Body-composition

KW - Nitrogen losses

KW - Amino-acids

KW - Normal men

KW - Protein

KW - Metabolism

KW - Kinetics

KW - N-15

KW - Fat

U2 - 10.1079/BJN2003859

DO - 10.1079/BJN2003859

M3 - Article

C2 - 12844395

VL - 90

SP - 221

EP - 231

JO - British Journal of Nutrition

JF - British Journal of Nutrition

SN - 0007-1145

IS - 1

ER -