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|Title: ||Postprandial studies of moderate exercise and triacylglycerol metabolism|
|Authors: ||Gill, Jason M.R.|
|Issue Date: ||1999|
|Publisher: ||© Jason Martin Ragnold Gill|
|Abstract: ||Exaggerated postprandial lipaemia has been implicated in the development of
atherosclerosis. Thus, by reducing postprandial TAG concentrations, exercise may
play a role in delaying atherogenic progression. This thesis sought to explore the
qualitative nature of, and the mechanisms behind, the moderate exercise-induced
attenuation to postprandial lipaemia.
Before the experimental studies commenced, a reproducibility study was
undertaken. This showed that in a group of eight middle-aged men, the postprandial
plasma TAG response differed by only 1.9 ± 5.1 % (mean ± standard error) on a testretest
basis, indicating that the oral fat tolerance test had enough precision to detect
the effect of exercise on TAG metabolism.
Previous work suggested that the exercise-induced reduction to lipaemia was
linked to the energy expended by exercise. As the attenuation may have been
mediated by energy deficit, rather than exercise per se, a study comparing the effect
of a 90-minute moderate exercise session with an equivalent dietary-induced energy
deficit on postprandial lipid metabolism was undertaken, in a group of eleven postmenopausal
women. This showed that the reduction in postprandial lipaemia elicited
by exercise was far greater than that elicited by intake-restriction (20 % vs. 7 %).
The second experimental study aimed to establish the effect of a 90-minute
moderate exercise session on postprandial chylomicron- and very-Iow-density
lipoprotein (VLDL)-TAG concentrations, and its effect on exogenous (through use of
a l3e-Iabelled lipid) and endogenous fat oxidation, in a group oftwelve middle-aged
men. Exercise reduced postprandial lipaemia by 23 %, and over three-quarters of this
reduction was due to lower VLDL-TAG concentrations. Increases in endogenous fat
oxidation accounted for over half of the increase in postprandial fat oxidation.
In the third experimental study, the effect of a 90-minutes moderate exercise
session on Intralipid clearance, and postprandial lipaemia, was determined in a group
of eight middle-aged men. Exercise attenuated postprandial lipaemia by 18 %, but
did not increase Intralipid clearance.
Taken together, these data imply that moderate exercise predominantly
reduced postprandial TAG concentrations by reducing hepatic VLDL secretion, rather
than increasing TAG clearance, and this effect is not mediated by whole-body energy
deficit. In addition, this work has shown that moderate exercise is effective at
attenuating postprandial lipaemia in middle-aged men and postmenopausal women.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Sport, Exercise and Health Sciences)|
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