Vol. 92, Issue 5, 2061-2070, May 2002
Metabolic and appetite responses to prolonged walking under
three isoenergetic diets
P. N.
Ainslie1,
K.
Abbas2,
I. T.
Campbell2,
K. N.
Frayn3,
M.
Harvie2,
M. A.
Keegan2,
D. P. M.
MacLaren1,
I. A.
Macdonald4,
K.
Paramesh2, and
T.
Reilly1
1 Research Institute for Sport and Exercise
Sciences, Liverpool John Moores University, Liverpool L3 2ET;
2 University Department of Anaesthesia, University
Hospitals of South Manchester, Withington Hospital, Manchester M20
2LR; 3 Oxford Lipid Metabolism Group, Radcliffe
Infirmary, Oxford OX2 6HE; and 4 Department of
Physiology and Pharmacology, University of Nottingham Medical
School, Nottingham NG7 2UH, United Kingdom
The effects of three isoenergetic
diets on metabolic and appetite responses to prolonged intermittent
walking were investigated. Eight men undertook three 450-min walks at
intensities varying between 25-30 and 50-55% of maximal
O2 uptake. In a balanced design, the subjects were given
breakfast, snacks, and lunch containing total carbohydrate (CHO),
protein (P), and fat (F) in the following amounts (g/70 kg body mass):
mixed diet, 302 CHO, 50 P, 84 F; high-CHO diet, 438 CHO, 46 P, 35 F;
high-fat diet, 63 CHO, 44 P, 196 F. Substrate balance was calculated by
indirect calorimetry over the 450-min exercise period. Blood samples
were taken before exercise and every 45 min during the exercise period.
The high-fat diet resulted in a negative total CHO balance (
140 ± 1 g) and a lower negative fat balance (110 ± 33 g)
than the other two diets (P < 0.05). Plasma glucagon,
nonesterified fatty acids, glycerol, and 3-hydroxybutyrate were higher
with the high-fat diet (P < 0.05 vs. high CHO),
whereas plasam insulin was lower after high fat (P < 0.05 vs. mixed and high CHO). Subjective ratings of fatigue and appetite
showed no differences between the three trials. Although diet
influenced the degree of total CHO and fat oxidation, fat was the main
source of enery in all trials.
substrate balance; substrate oxidation
