Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine

Abstract

Background:The effects of food restriction on energy metabolism have been under investigation for more than a century. Data obtained are conflicting and research has failed to provide conclusive results. Objective: The objective of this study was to test the hypothesis that in lean subjects under normal living conditions, shortterm starvation leads to an increase in serum concentrations of catecholamines and thus to an increase in resting energy expenditure. Design: Resting energy expenditure, measured by indirect calorimetry, and hormone and substrate concentrations were measured in 11 healthy, lean subjects on days 1, 2, 3, and 4 of an 84-h starvation period. Results: Resting energy expenditure increased significantly from 3.97 ± 0.9 kJ/min on day 1 to 4.53 ± 0.9 kJ/min on day 3 (P < 0.05). The increase in resting energy expenditure was associated with an increase in the norepinephrine concentration from 1716. ± 574 pmol/L on day 1 to 3728 ± 1636 pmol/L on day 4 (P < 0.05). Serum glucose decreased from 4.9 ± 0.5 to 3.5 ± 0.5 mmol/L (P < 0.05), whereas insulin did not change significantly. Conclusions: Resting energy expenditure increases in early starvation, accompanied by an increase in plasma norepinephrine. This increase in norepinephrine seems to be due to a decline in serum glucose and may be the initial signal for metabolic changes in early starvation.Am J Clin Nutr 2000;71:1511-5.

Glucose uptake in human brown adipose tissue is impaired upon fasting-induced insulin resistance

“…Consistent with previous publications [37,38], we found that BMR was increased upon fasting, most likely due to increased whole-body sympathetic activity, as indicated by the elevated epinephrine levels. Furthermore, we found that NST was decreased upon fasting, which can be partly explained by higher BMR, and we found a correlation between BAT glucose uptake rate and NST at baseline, but not in the fasted state.…”

Effect of an acute fast on energy compensation and feeding behaviour in lean men and women

“…Both the anthropometric and biochemical Energy compensation after a short term fast AM Johnstone et al measurements provided no evidence that compliance was poor, since the results are consistent with those obtained in other well-documented starvation studies. 12,13 There was, however, a pronounced change in feeding behaviour for the first meal after the fast. Subjects preferentially selected a higher-fat intake, perhaps as a mechanism to increase energy intake by choosing the most energy-dense foods.…”

Metabolic changes in malnutrition

“…13,14 This probably reflects the high rate of gluconeogenesis that occurs at this time. As fasting progresses, however, metabolic rate decreases as free T 3 and catecholamine levels decrease and the rate of gluconeogenesis decreases.…”