Eur J Appl Physiol (1993) 66:445-450 European Applied Journal of

Physiology and Occupational Physiology © Spfinger-Verlag 1993

The effects of a high carbohydrate diet on postprandial energy expenditure during exercise in rats

Shinichi Saitoh, Tatsuhiro Matsuo, and Masashige Suzuki

Laboratory of Biochemistry of Exercise and Nutrition, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan

Accepted January 22, 1993

Summary. Whether or not a high intake of carbohy- drate increases postprandial energy expenditure during exercise was studied in rats. The rats were meal-fed reg- ularly twice a day (0800-0900 hours and 1800-1900 hours) on either a high carbohydrate (CHO) (carbohy- dra te / fa t /p ro te in = 70/5/25, % of energy) or high fat (FAT) (35/40/25) diet for 12 days. On the final day of the experiment, all of the rats in each dietary group were fed an evening meal containing equal amounts of energy (420kJ .kg -1 body mass). After the meal, they were divided into three subgroups: pre-exercise control (PC), exercise (EX), and resting control (RC). The P C - C H O and PC-FAT groups were sacrificed at 2030 hours. The EX-CHO and EX-FAT groups were given a period of 3-h swimming, and then sacrificed at 2330 hours. The RC-CHO and RC-FAT groups rested after the meal and were sacrificed at 2330 hours. Total energy expenditure during the period 1.5 h f rom the commencement of exercise was higher in EX-C HO than in EX-FAT. The respiratory exchange ratio was also higher in EX-CHO than in EX-FAT, suggesting enhanced carbohydrate oxi- dation in the former. Compared with both PC-FAT and RC-FAT, the liver glycogen content of EX-FAT rats was significantly decreased by exercise. On the other hand, the liver glycogen content of both EX-C HO and RC-CHO was higher than that of P C - C H O rats. The glycogen content of soleus muscle of EX-FAT was slightly decreased during exercise, however, that of EX- CHO increased significantly. Thus postprandial energy expenditure during exercise was higher in the rats fed the CHO diet than in those fed the FAT diet, which could have been related to the increase of both liver and mus- cle glycogen storage during exercise in the former.

Key words: High-carbohydrate diet - Oxygen consump- tion - Prolonged exercise - Glycogen - Liver - Muscle - Rat

Correspondence to: S. Saitoh

Introduction

Exercise has been shown to have a beneficial effect on diet therapy for obese individuals who wish to reduce their body fat (LeBlanc 1988). From the practical view- point, the question often raised is when during the day the exercise should be performed in order to maximize its thermogenic effect. It has been reported that exercise before a meat enhances the thermogenic response to the meal in humans (Bahr et al. 1987; Bielinski et al. 1985; Maehlum et al. 1986), whereas, the effects of exercise after a meal on diet-induced thermogenesis is unclear in humans. Segal and Gutin (1983), and Segal et al. (1984, 1985, 1992) have reported enhanced postprandial energy expenditure during exercise. However, other researchers have failed to show any interaction between exercise and diet-induced thermogenesis (Dallosso and James 1984; Hickson et al. 1986; Pacy et al, 1985; Schutz et al. 1987). In addition, there are few studies which have examined the effects of the types of diet, high carbohy- drate or high fat, on postprandial energy expenditure during exercise in humans (Abbott et al. 1990) and in rats (Gleeson and Waring 1986).

The purpose of this study was to examine the effect of a high carbohydrate diet, compared with a high fat diet, on postprandial energy expenditure during exercise with respect to liver and muscle glycogen contents in rats.

Methods

Animals. A selection of 30 male Sprague-Dawley rats (3 weeks- old), bred in the Animal House of the Institute of Health and Sport Sciences, University of Tsukuba, were used for the study which was approved by the Ethics Committee of the Institute of Health and Sport Sciences. Half of the rats were fed a high carbo- hydrate (CHO) diet and the half were fed a high fat (FAT) diet. The composition of each diet has been described previously (Shi- momura et al. 1990). The CHO diet provided 70°/0, 5070, and 25O7o of energy as carbohydrate, fat, and protein, respectively, the FAT diet 35°70, 40%, and 25°70, respectively. The animals were housed individually at an ambient temperature of 23 °C, with light from 0700 and 1900 hours and with free access to water.

446

Experiment. Both groups of the rats were fed ad libitum for 11 days, and then all the rats were meal-fed regulary twice a day (0800-0900 hours and 1800-1900 hours) for 12 days. During the regular feeding period, to examine urinary excretion of catecolam- ines, 6 rats from each dietary group were randomly selected and placed in individual metabolic cages for 48 h. Urine was collected into a glass cylinder containing hydrochloric acid and then stored at -80 °C for later analysis. Also during this period, all the rats were subjected to swimming exercise three times (10 rain) to elimi- nate the emotional stress of novelty. The swimming exercise was performed in the same manner as described previously (Saitoh et al. 1992). On the final day of the experiment, all of the rats in each dietary group were fed a final meal containing the same amount of energy, 420 kJ.kg-I body mass (average amount for an evening meal for the rats fed the CHO diet), in their own cages at 1800-1900 hours. They were then divided into three subgroups: pre-exercise control, exercise, and resting control. The pro-exercise control rats were sacrificed at 2030 hours before exercise. From each exercise subgroup 5 rats exercised for 3 h starting at 2030 hours by swimming with a sinker corresponding to 1% their body mass. During swimming, oxygen uptake and respiratory exchange ratio (R) were measured. Exercise and resting control rats of both dietary groups were sacrificed at 2330 hours. To examine the ef- fect of the final meal on resting energy expenditure, 6 rats of each dietary group were randomly selected and the resting oxygen con- sumption was measured before and after the meal between 1700- 2200 hours on 3 days before the final day.

Urinary adrenaline (A) and noradrenaline (NA) were assayed by high-pressure liquid chromatography with electrochemical de- tection. A quantity of 500 ~tl of urine extract were added to 250 gl of 13 mmol'1-1 Na2S205, 50ng of dihydroxybenzylamine (inter- nal standard), 1 ml of 1 tool. 1-i TRIS(hydroxymethyl)aminome- thane-(TRIS) HC1 buffer (pH 8.6) containing 1% ethylenediami- netetra-acetic acid (EDTA), and 30 mg of acid-washed alumina. This mixture was stirred for 15 min. After decanting, the alumina was washed three times with 5 ml of distilled water. After centrifu- gation the supernatant was removed. The catecholamines (A, NA, and dihydroxybenzylamine) fixed on the alumina were eluted with 100 gl 0.22 tool . l - ' acetic acid, 0.15 mmol.1-1 sodium metabis- sulphite, and 0.025% EDTA in an Eppendorf tube and shaken and filtered through a Millipore Millex HV4 filter (Yonezawa, Ja- pan). A 10-gl sample of the extract was injected into a reverse phase analytic column (CA-50DS, I50x4.6 ram, Eicom, Kyoto, Japan) of a Shimazu high-pressure liquid chromatography system (Kyoto, Japan). The mobile phase consisted of 100 mmol' l-1 cit- ric acid, 100 mmol.1 -~ sodium acetate, 1 mmol'1-1 EDTA, 1 retool.1-1 sodium octylsulphonate, and 15% methanol. The flow rate of the mobile phase was fixed at 1 ml 'min -~. An elec- trochemical detector (model ECD-100, Eicom, Kyoto, Japan) was used (potential 0.6 V).

Statistical analsys. The significance of difference between groups was tested by Student's unpaired t-test.

Measurement of oxygen uptake and R during rest and exercise. To measure the resting oxygen consumption, the rats were placed in a glass chamber (150 mm inner-diameter and 100 mm inner-height). On the other hand, the exercising rats were placed in a swimming chamber: the chamber was a methyl methacrylate cylinder measur- ing 190ram in diameter and 500 mm deep (Baker and Horvath 1964). The gas phase of the swimming chamber above the water was kept at a volume of approximately 0.6 1 and was airtight when the lid was fastened. The water temperature was 35°C during measurement. The room temperature was 21 + 1°C, and room air was continuously pumped at a flow rate of 0.701" min- ~ into both types of chamber through a small aperture (10 mm in diameter). All the air was collected into a Douglas bag (Fukuda Sangyo, To- kyo, Japan), the bag being changed every 30 rain during the rest- ing measurements, whereas air was collected during exercise at 0.5-1 h, 1-1.5 h, 1.5-2.5 h, and 2.5-3 h from the commencement of the exercise. The concentrations of oxygen and carbon dioxide in the air collected were immediately analysed by a gas mass ana- lyser (MGA 1100. Perkin-Elmer, St. Louis, Mo.).

The time lags of both systems were determined by injecting various volumes of oxygen into the chamber (or air-space above the water) and sampling the oxygen contents of the outflowing gas continuously with a gas analyser (RAS-31, AIC Co., Tokyo). The time response was 45 s.

Tissue collection and analyses. The rats were sacrificed by decapi- tation. Blood was collected to obtain serum. Portions of the large- st lobe of liver and soleus muscles of both legs were rapidly re- moved and freeze-clamped in liquid nitrogen. All samples were stored at - 80 °C until analysis.

Serum glucose was determined by the method reported pre- viously (Suzuki et al. 1984). Serum free fatty acids (FFA) and se- rum triacylglycerol (TG) were determined enzymatically using kits (NEFA C-Test) and (Triglyceride G-Test), respectively, purchased from Wako Pure Chemical, Co., Osaka. Serum 3-hydroxybuty- rate (3-OHBA) was determined enzymatically using a kit (F-kit, D-3-hydroxybutyrate) purchased from Boehringer Mannheim-Ya- manouchi, Inc., Tokyo. Serum immunoreactive insulin (IRI) was determined by radio-immunoassay using a kit (insulin immuno-as- say kit) purchased from Amersham Pharmaceutical Co., Ltd., To- kyo.

Tissue glycogen contents were determined according to the method of Loet al. (1970).

Results

Urinary A and N A

Urinary excretion of A measured for 6 rats for each die- tary group was 87.7 (SEM 7.5) n g . d a y -1 for the C H O diet group and 56.4 (SEM 4.2) r i g , da y - 1 for the F A T diet group, and these values were significantly different ( P < 0 . 0 1 ) . Ur ina ry excretion of NA was 535 (SEM 31) n g . d a y -1 for the C H O diet group and 504 (SEM 21) ng. d a y - 1 for the F A T diet group, and these values were no t different .

Body and tissue mass

The initial body mass of the rats fed the F A T diet was no t different f rom that of those fed the C H O diet bu t a significant difference in final body mass was observed between the two dietary groups (Table 1). Liver and ab- domina l adipose tissue masses of rats fed the F A T diet were heavier t han those fed the C H O diet but this differ- ence was no t observed in soleus muscle mass.

Swimming exercise decreased the body mass of both dietary groups: the reduct ion of body mass (difference in body mass between jus t before and after exercise) was 10 (SEM 1) g for the F A T group, and 7 (SEM 1) g for the C H O group, NS.

Oxygen consumption and R during rest and exercise

Resting oxygen consumpt ion was measured for 1 h be- fore and for 3 h after the meal to assess the thermogenic effects of the diets (Fig. 1). However, a thermogenic ef- fects of food was not detected in either dietary group.

Table 1. Body and tissue mass

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Body mass (g) Tissue mass (g)

Initial Final Liver Soleus muscle Adipose tissues a

Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM PC-CHO (5) 84 3 152 3 5.988 0.097 0.130 0.006 1.045 0.184 PC-FAT (5) 85 5 166 5* 7.565 0.281' 0.128 0.007 1.633 0.152

EX-CHO (5) 83 4 151 2 6.155 0.127 0.122 0.003 1.044 0.126 EX-FAT (5) 80 5 163 5 6.898 0.226* 0.110 0.007 1.409 0.108

RC-CHO (5) 83 1 152 3 6.163 0.078 0.130 0.005 0.983 0.148 RC-FAT (5) 94 3 172 5* 7.850 0.244* 0.134 0.007 1.170 0.125

CHO (15) 84 1 152 1 6.102 0.059 0.128 0.003 1.024 0.083 FAT (15) 86 3 167 3* 7.408 0.174" 0.123 0.005 1.421 0.087*

PC, Pre-exercise control; EX, exercise, RC, resting control; * significantly different from carbohydrate (CHO) diet group abdominal (epididymal, perirenal, and mesenteric) adipose tis- (/'<0.05)

sue;

7 Z O

I - o - _ - ' 6

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Z E

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g 4

3

1.2

- - C - e - - - F A T

- - L ~ & - - C H O * E v

z o

o Z W

I I , [ , , , , , 1 , x 0

n ' l " 0

0.8 * i

Meal Swimming r , , , , , 1

1'7 1~8 1~9 2'0 21 22 23 2'4 Time of Day(h)

Fig. 1. Oxygen consumption (top) and respiratory exchange ratio (R, bottom) during rest (A, O) and exercise (&, 0). AA, carbo- hydrate (CHO) diet group, 00 , FAT diet group. Resting oxygen consumption was measured for six rats in each dietary group on 3 days before the final day [body mass, 142 (SEM 4) g for the CHO group, 153 (SEM 4) g for the FAT group]. On the final day, oxygen consumption was measured for five rats in each group during a period of 3-h swimming. For details see text. Each point represents mean and SEM. * Significant difference between the two groups (P<0.05)

The average values o f total resting oxygen consumpt ion for 1 h before and for 3 h after meals were not different between the two groups; C H O versus FAT, 312 (SEM 11) versus 338 (SEM 8) m l . r a t - I . 1 h - I , and 930 (SEM 6) versus 1019 (SEM 15) m l . r a t -1 -3 h -1. On the other hand, the R values for 3 h after meals appeared to be higher at all times with the C H O diet than with the FAT diet. The average values for the period were 1.11 (SEM 0.01) for the C H O diet group and 0.96 (SEM 0.02) for

900

7 0 0

500

30@

0I

"-i-

11111T fll IT 0 . 5 - 1.5 1.5 - 3

EXERCISE TIME (h)

Fig. 2. Total oxygen consumption between 0.5 and 1.5 h, and between 1.5 and 3 h from commencement of the exercise in the rats fed the carbohydrate diet (open bar) and in those fed the FAT diet (hatched bar). Each value (mean and SEM) was calcu- lated from the data in Fig. 1. * Significant difference between the groups (P< 0.05)

the FAT diet group, and these values were significantly different ( P < 0.001).

Oxygen consumpt ion during exercise was measured for 2.5 h, beginning 0.5 h after the commencement o f the exercise (Fig. 1). Oxygen consumpt ion between 0.5 and 3 h appeared to be greater in the C H O diet group than in the FAT diet group. The sum o f oxygen con- sumpt ion between 0.5 and 1.5 h, but not between 1.5 and 3 h, was significantly different between the two groups (Fig. 2). The R value for 3-h swimming also ap- peared to be higher in the C H O diet group than in the FAT diet group. The average values for the period were 0.90 (SEM 0.01) for the C H O diet group and 0.83 (SEM 0.01) for the F A T diet group, and these values were sig- nificantly different ( P < 0.01).

448

Table 2. Serum glucose, free fatty acids (FFA), 3-hydroxybutyrate concentrations

(3-OHBA), triacylglycerol (TG), and immunoreactive insulin (IRI)

Serum glucose FFA 3-OHBA TG IRI

(mmol. ml - 1) (gmol. 1 - 1) (mmol. 1 - 1) (mmol. 1 - 1) (~tU. ml - 1)

Mean SEM Mean SEM PC-CHO (5) 8.6 0.3 249 48 PC-FAT (5) 8.5 0.1 359 44 EX-CHO (5) 8.6 0.5 408 67 EX-FAT (5) 8.9 0.3 388 28 RC-CHO (5) 7.9 0.2 372 35 RC-FAT (5) 8.3 0.2 357 51

Mean SEM Mean SEM Mean SEM 0.070 0.004 0.69 0.06 55.6 7.2 0.179 0.022 b 1.10 0.17 48.7 6.0 0.204 0.049 a 0.44 0.02 a 38.8 7.1 0.364 0.087 0.52 0.02 b 29.2 1.4 a 0.137 0.024" 1.55 0.28 ~' ~ 42.5 5.9 0.159 0.032 0.87 0.24 40.7 7.1

a Significantly different from PC rats in the same diet (P< 0.05); b significantly different from carbohydrate (CHO) diet group (P<0.05);

c significantly different from EX rats in the same diet (P<0.05);~ for other definitions see Table 1

Table 3. Glycogen contents of soleus muscle and liver

Soleus Liver

(mg .g - 1) (mg. rat - 1) (mg. g - 1) (mg. rat - 1)

Mean SEM Mean PC-CHO (5) 4.58 0.41 0.56 PC-FAT (5) 3.33 0 .10 b 0.43 EX-CHO (5) 5.56 0.17 0.72 EX-FAT (5) 3.67 0.10 u 0.40 RC-CHO (5) 5.02 0.28 0.65 RC-FAT (5) 3.85 0.11 b 0.52

SEM Mean SEM Mean SEM 0.04 45.3 1.8 271 20 0.03 b 46.1 1.5 348 16 b'c

0.04 a 56.3 3.1" 347 22 a 0.02 u 38.3 3.8 b 266 30 0.05 60.8 1.8 a 375 10 a 0.03 b 48.8 1.8 b' ° 383 20 c

" Significantly different from PC rats in the (P< 0.05); b significantly different from CHO group (P< 0.05);

same diet c significantly different from EX rats in for other definitions see Table 1

the same diet (P<0.05);

Serum glucose, FFA, 3-OHBA, TG, and IRI concentrations

Serum glucose, F F A , and IRI concen t ra t ions at all t imes were similar in bo th d ie ta ry groups (Table 2). Serum 3- O H B A concen t ra t ions at pre-exercise were s ignif icant ly h igher in the F A T diet g roup t han in the C H O group . Serum 3 - O H B A concen t ra t ions increased in exercised and rest ing con t ro l rats fed the C H O diet . Serum T G concen t ra t ions at pre-exercise were s imilar in bo th dieta- ry groups . Exercise decreased serum T G concen t ra t ions in the C H O diet group. There were s ignif icant d i f fer - ences in serum T G concen t ra t ions be tween pre-exercise and rest ing con t ro l rats in the C H O diet g roup .

Soleus muscle and liver glycogen contents

The g lycogen content o f soleus muscle, at all t imes, was higher in the C H O diet g roup than in the F A T diet g roup (Table 3). Exercise increased soleus muscle gly- cogen content in the C H O group and decreased it in the F A T group . Liver g lycogen concen t ra t ions at pre-exer- cise were s imilar in bo th d ie ta ry groups ; however , whole liver g lycogen content was higher in the F A T diet g roup than in the C H O diet g roup . Dur ing exercise, liver g l y -

cogen content was increased in the C H O diet g roup bu t decreased in the F A T diet g roup . In the C H O diet g roup , c o m p a r e d with pre-exercise cont ro l , rest ing con- t ro l rats showed e levated liver g lycogen contents , bu t this was not observed in the F A T group .

Discussion

In the present s tudy, oxygen c o n s u m p t i o n dur ing the first ha l f o f the 3-h pe r iod o f swimming was higher in rats fed the C H O diet t han in those fed the F A T diet and it is no t ewor thy tha t l iver and muscle g lycogen con- tents increased dur ing exercise in the fo rmer group .

Gleeson et al. (1982) have prev ious ly r epor t ed , using mea l - fed rats , tha t seden ta ry rats d id not show signifi- cant d ie ta ry - induced thermogenes is when they were at rest, whereas l ight runn ing on a t readmi l l po t en t i a t ed d ie ta ry - induced thermogenes is in this g roup as well as in the t r a ined g roup . These t rends were also observed in the present s tudy. However , the mechan i sms respons ib le for the enhanced the rmogen ic effect o f the meal dur ing exercise was not clear.

To ta l c a r b o h y d r a t e u t i l iza t ion can be es t imated f rom oxygen c o n s u m p t i o n and R in 3-h swimming by using the equat ion; G = 1202 (R-0 .7) x 1 .22/0.30 × 0.91 (Gor-

449

Table 4. Estimation of carbohydrate utilization from oxygen consumption and respiratory exchange ratio (R)

Group Exercise 1202 R Carbohydrate time (h) (ml. min. kg- 1) (mg)

0-1.5 61.1 746 CHO O.9O 1382

1.5-3.0 52.1 636 0-1.5 50.9 444

FAT 0.83 850 1.5-3.0 46.5 406

~r02, Oxygen consumption. The body mass of the rats averaged 167 g for the FAT group and 152g for the CHO group. Carbo- hydrate (G) was calculated from the equation (Gorostiaga et al. 1988), G= 1202 (R -0.7) × 1.22/0.30 x 0.91, where G is carbohy- drates of glycosil units used during exercise, 1202 is 1202 in stea- dy-state (1" min-1, multiplied by the exercise duration in min), R is respiratory exchange ratio in steady-state (1.22 kJ'l-1 of 02 burnt per glucosyl unit), and 0.91 is kJ'g -~ of glucosyl units burnt with 02

ostiaga et al. 1988) where G is the carbohydrates of gly- cosyl units used during exercise (Table 4). The results showed that carbohydrate oxidation appeared to be higher in the CHO group than in the FAT group. In- creased carbohydrate oxidation with enhanced liver and muscle glycogen synthesis has suggested increased rates of substrate ('futile') cycling and consequently extra en- ergy required for the CHO group (Bahr et al. 1987).

Since the abdominal fat mass was larger in the FAT group than in the CHO group, one could suppose that this might have led to differences in the whole body fat content and consequently in the energy cost of swim- ming between the two groups. Lately, Gleeson and War- ing (1986) have shown that body mass and carcass fat mass (per rat and also per unit of body mass) were larger in rats fed a high fat diet than in rats fed a high carbohydrate diet, and during exercise the oxygen con- sumption, expressed per rat, was higher in the former than in the latter but expressed per unit of body mass per unit of time, was similar in both groups. These re- suits would suggest that the total body fat content may not have influenced the work output during swimming in the rats. However, further study is needed to clarify this point.

The present observations do not agree with the result of the study by Gleeson and Waring (1986), especially during the first half of the 3-h exercise period. Although the system of feeding meals and the composition of the high carbohydrate diet in both studies were similar, there were some differences in detail - strain and ages of rats, and daily meal time. The most important differ- ence was the time after the final meal, i.e. 1.5 h in our study, and 17 h (without morning meal) in the study of Gleeson and Waring. We would suggest that diurnal changes in liver and muscle glycogen concentrations may have caused the differences between the studies.

It has been well understood (Hawley et al. 1992) that the type of pre-exercise meal significantly affects muscle energy metabolism during prolonged exercise, and con- sequently exercise performance. Since elevated liver gly-

cogen directly increased liver glycogenolysis and glucose production (Vissing et al. 1989), increased hepatic glu- cose production may facilitate muscle glucos e uptake, and consequently enhance glucose oxidation or muscle glycogenesis. In the present study, soleus muscle glycog- en content in rats fed the CHO diet increased rather than decreased after exercise, and also liver glycogen concentrations increased during exercise. In addition, we have previously reported (Suzuki et al. 1984) that the glycogen content of liver and soleus muscle significantly increased during light running in rats fed a high sucrose diet before exercise. From these results, liver and muscle glycogen synthesis in the CHO group might have been increased during exercise, and consequently oxygen con- sumption increased. However, further study is needed to explore the relationship between oxygen consumption and glycogen metabolism during exercise.

Since it has been known (Astrup et al. 1989) that the thermogenic effect of carbohydrate has a component mediated by the sympatho-adrenal system, increased urinary A excretion in rats fed the CHO diet might have been related to enhanced postprandial thermogenesis during exercise.

Previous studies have demonstrated de novo lipogen- esis in animals (Masoro 1962), and it has been shown that fat synthesis from carbohydrate is a quantitatively significant process in meal-fed rats (Chakrabarty and Leveille 1968). In addition, it has been reported (Ache- son et al. 1982, 1984) that de novo lipogenesis occurs when R is above 1.0. In the present study, compared with pre-exercise controls, serum TG concentrations of resting controls showed significant increase in the CHO group. These results seemed to indicate that the liver glycogen content of resting controls was nearly maximal at about 5 h after the evening meal so that the excess carbohydrate was used for fat synthesis. Conversely, exercise reduced blood TG concentrations in the CHO group, because de novo lipogenesis might have been suppressed during exercise.

Finally, the present study showed that light exercise shortly after a carbohydrate-rich diet resulted in en- hanced muscle glycogen synthesis. If this is true then in the preparation before a sports event, light exercise 'warming-up' before the event may not only elevate body temperature but also supply a considerable pro- portion of the glucose to the muscle and increase the glycogen stores.

In summary, the CHO diet-fed rats, compared with the FAT diet-fed rats, showed higher oxygen consump- tion during the early period of prolonged exercise, and this might have been related to enhanced glycogenesis in the liver and muscle by the high-carbohydrate diet.

Acknowledgement. This study was supported in part by a grant from the University of Tsukuba Project Research Fund.

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