Ee. Blaak et al., BETA-ADRENERGICALLY MEDIATED THERMOGENIC AND HEART-RATE RESPONSES - EFFECT OF OBESITY AND WEIGHT-LOSS, Metabolism, clinical and experimental, 44(4), 1995, pp. 520-524
beta-Adrenergically mediated thermogenic and heart rate (HR) responses
, as assessed by stepwise intravenous infusion of the beta-agonist iso
prenaline (ISO), were evaluated by partial regression analysis in a gr
oup of men with a wide range of body fat (n = 30) and in a subgroup of
16 obese men after weight loss, beta-Adrenergically mediated thermoge
nesis (open-circuit ventilated-hood system) was blunted in obese subje
cts, as reflected by a significant positive correlation between percen
t body fat (hydrostatic weighing) and the plasma ISO concentration nee
ded to increase resting energy expenditure (EE) by 15% (P <.001). The
magnitude of the beta-adrenergically mediated HR response was (negativ
ely) associated with the basal plasma norepinephrine (NE) concentratio
n (P <.001). Weight reduction resulted in a significant increase in th
ermogenic and HR responses in obese subjects. Furthermore, the increas
e in thermogenic response as a result of weight loss was negatively re
lated to the magnitude of thermogenic response (P <.01) and positively
related to the initial percent body fat (P <.05). The increase in HR
response as a result of weight loss was positively related to the decr
ease in basal NE (P <.01) and the change in percent body fat (P <.05).
In conclusion, the degree of adiposity was shown to be negatively rel
ated to the magnitude of p-adrenergically mediated thermogenesis, wher
eas the HR response was merely related to basal NE, Since weight loss
resulted in a significant increase in the thermogenic response, the bl
unted P-adrenergically mediated thermogenesis does not seem to be a pr
imary factor contributing to the development of obesity. Copyright (c)
1995 by W.B. Saunders Company