J Nutr Sci Vitaminol, 49, 163-167, 2003

(-)-Hydroxycitric Acid Ingestion Increases Fat Utilization During Exercise in Untrained Women

Kiwon LIM1, Sungpil Ryu2, Ho-Sung NHO3, Sung-Keun CHOI4, Taedong KWON5, Heajung SUHI, Jaemoo Sob, Kyoko TOMITA7, Yasuhide OKUHARA7 and Norihiro SHIGEMATSU7

1 Department of Physical Education, Kornkuk University, Seoul, Korea2 Kyungpook National University, Daegu, Korea

3 Department of Sports Medicine, Kyung-Hee University, Suwon, Korea4 Kyung-In Women's College, Incheon, Korea

5 Sangju National University, Sangju, Kore6 Institute of Elderly Health, Seoul, Korea

7 Food Products Division, Central Research Laboratory, Fancl Co., Yokohama, Japan

(Received August 30, 2002)

Summary (-)-Hydroxycitric acid (HCA) is a competitive inhibitor of the enzyme ATPci-trate-lyase, which inhibits lipogenesis in the body. Moreover, HCA increases endurance exercise performance in trained mice and athletes. However, had not been investigated in untrained animals and humans. Therefore, we investigated the effects of short-term HCA ingestion on endurance exercise performance and fat metabolism in untrained women . In two experiments designed as a double-blind crossover test, six subjects ingested 250mg of HCA or placebo (same amount of dextrin) via capsule for 5d and then participated in cycle ergometer exercise. They cycled at 40% VO2max for 1h and then the exercise intensity was increased to 60% VO2max until exhaustion on day 5 of each experiment . HCA tended to decrease the respiratory exchange ratio (RER) and carbohydrate oxidation during 1h of exercise. In addition, exercise time to exhaustion was significantly enhanced (p<0.05). These results suggest that HCA increases fat metabolism, which may be associated with a decrease in glycogen utilization during the same intensity exercise and enhanced exercise

performance.Key Words hydroxycitrate, RER, fat oxidation, exercise

Many researchers have investigated endurance exercise performance in trained subjects. However, untrained-state must also be emphasized because, not only enhancement of exercise performance in trained athletes, but also health promotion is important and meaningful to people.

Energy utilization systems during exercise are different with or without training state. For example, endurance exercise training reduces malonyl-CoA concentration (1) and increases mitochondria content (2), mitochondrial uptake of long-chain fatty acids (3), and fatty acid binding protein expression (4). Therefore, fatty acid oxidation is increased. In these situations, the ingestion of some supplements that cause increased lipid oxidation might have a positive effect on fat utilization. Caffeine ingestion, however, causes more lactate

production and accumulation followed by shortened endurance exercise time in untrained subjects (5): otherwise, trained sub jects show higher plasma free fatty acid (FFA) concentration and delayed exercise time to exhaustion (6).

(-)-Hydroxycitric acid (HCA) is known to reduce body fat accumulation after a few weeks of ingestion (7), resulting in a decrease in appetite (8). HCA, a

E-mail: kwlim2l@hotmail.com

potent inhibitor of ATP citrate-lyase (EC 4.1.3.8, 9), inhibits fatty acid synthesis and reduces appetite in rodents (10). However, there are few articles considering HCA ingestion in relation to exercise performance . Ishihara et al. (11) reported that HCA ingestion for 13d increases fat oxidation and endurance exercise time about 43% compared to a control placebo in mice . These findings have been confirmed for human athletes as well (12).

A previous study regarding controlled HCA ingestion was performed with only trained subjects (13). Therefore, in the present study we investigated how HCA affects energy substrate utilization and endurance exercise performance in untrained women.

METHODS

Subjects. Six females agreed to participate in the study after being informed of the nature of the experiments. Subjects were nonsmokers and draink alcoholic beverages socially 2-3 times a month. They did not take any kind of drug or pharmaceutical and had not partaken in any type of exercise training for at least the

past 6 mo. We did not control their food consumption or private lifestyle. However, lipolytic food consumption like caffeine in coffee, green tea and black tea was inhibited during the experimental period except for cap

163

164 LIM K et al.

Table 1. Physical characteristics of the subjects.

Values are mean and standard deviation (n=6).

saicin resultant from the intake of Kimuchi, a tradi

tional Korean food, considering the dietary habits of

Koreans. Their physical characteristics are presented in

Table 1.

Each subject signed a written consent form that out

lined possible risks of the procedures. The nature of the

study, approved by the institutional ethics committee in

Kyung-Hee University and the Helsinki Declaration of

1975, was explained to all subjects, who thereafter gave

their written informed consent to participate.

Experimental procedures, Subjects reported to the

laboratory 1 wk before the start of the experiment for

an incremental maximum oxygen consumption

(VO2max) test on a cycle ergometer as reported by Lim

et al. (14). Their mean VO2max was 26.07•}2.79ml/kg-1/min-1

. We calculated the exact 40% and 60% of

each VO2max exercise bout based on their VO2max.

HCA or a placebo was ingested for 5d in a double-blind

crossover manner. At least 2d between trials was estab

lished to minimize any possible effects of HCA.

Experimental design. The protocol for each trial was

designed in the same manner. Subjects reported to the

laboratory 2h before the start of the experiment

(07:00). They ingested a 640 kcal meal (breads, eggs,

and orange juice) and 250mg of HCA (water-soluble

type) or placebo 2h before exercising as reported previ

ously (5), Exercise was conducted at the time of peak

HCA concentration in the blood (13). After the meal,

subjects were allowed to rest in a seated position. After

resting for 100min, they warmed up with 5min of

stretching exercises 10min prior to beginning exercise.

During the resting periods, a venous 3-way catheter

was inserted into the antecubital vein and was kept

silent with a saline infusion. A resting blood sample and

expired gas were collected and analyzed.

The subjects exercised using a bicycle ergometer

(Combi Aerobike, 75TXL-2, Japan) at a pedaling fre

quency of 50rpm and an intensity of 40% of VO2max

for 60min and then the intensity was elevated to 60%

until exhaustion. The protocol of two different exercise

intensities (40% for 60min and 60% VO2max exercise

until exhaustion) was selected to investigate endurance

performance reported by other researchers (5, 13, 14).

Samples for expired air were analyzed every 15min for

60min during exercise at 40% VO2max. Blood samples

(5ml) were taken every 15min for 60min during exer

cise at 40% VO2max. The investigators determined

exercise time to exhaustion when the cadence of

50rpm could no longer be maintained in three different

1min periods. Subjects did not have any indication of

time after the 60min sampling period until exhaustion.

Fig. 1. Experimental design.

The experimental procedure was performed in a labora

tory with a room temperature of 20•Ž and 50% humid

ity The experimental design is shown in Fig. 1.

Analysis, Expired gas samples were analyzed using

an auto-analyzer (Sensor Medic, Vmax 229, USA) pre

viously calibrated for 02 and CO2. Fat and carbohydrate

oxidation during exercise were calculated as previously

described (16).

Carbohydrate oxidation=4.585 VCO2-3.226VO2

Fat oxidation=1.695 VO2-1.701 VCO2

Blood samples were collected with an EDTA-coated

tube. Whole blood (500ƒÊL) was immediately separated

by microcentrifugation for blood glucose and lactate

analysis using an auto-analysis system (YSI 2300 Plus,

Yellow Springs Institute, USA). Another blood sample

was centrifuged and plasma was collected and stored in

a -70•Ž freezer for future free fatty acid (FFA) analysis.

Plasma FFA (NEFAzyme-Kit, Liken, Tokyo, Japan)

concentrations were determined by an enzymatic

method using a kit as we previously described (5, 14).

Statistical analysis. The results are described as

mean•}SE. The data were analyzed using Student's t

test in the same time point. The level of significance was

set at p<0.05.

RESULTS

Oxygen consumption and respiratory exchange ratio

The oxygen consumption increased a the initiation of

exercise and reached a plateau at 15min during exer

cise (Fig. 2A). The oxygen consumption at rest and dur

ing exercise was not different between the placebo and

HCA trials, indicating that the ingestion of HCA did not

affect VO2 at rest or during exercise for 60min. The

RER tended to be lower in the HCA trial than in the pla

cebo trial during 1h exercise, and was significantly dif

ferent between the trials at 30min (p<0.05; Fig. 2B).

HCA Ingestion on Fat Oxidation in Untrained Women 165

Fig. 2. VO2 (A) and RER (B) differences during 40%

VO2max cycle ergometer exercise. Values are means•}

SE. * Statistically significant from the values of the pla

cebo trial (p<0.05).

Carbohydrate and fat oxidationCarbohydrate oxidation (Fig. 3A) increased at the ini

tiation of exercise and slightly decreased during 1h exercise, but fat oxidation (Fig, 3B) increased in the late

period of exercise. Carbohydrate oxidation during the exercise period was not different between the HCA and

placebo trials. Fat oxidation in HCA trial tended to increase as compared to that in the placebo trial, but the difference was not significant. Blood measurements

The blood glucose levels were increased by consuming the meal (-120min) and slightly decreased during exercise in the HCA trial as compared to the placebo trial (Fig. 4A). The lactate levels during exercise were increased in placebo trial, but not to a significant degree (Fig. 4B). The FFA concentrations were decreased by consuming the meal and increased at the initiation of exercise (Fig. 4C), The levels during exercise were slightly lower in the RCA trial than in the placebo trial.Endurance exercise capacity

Exercise time to exhaustion at 60% VO2max after 40% VO2max for 60min was significantly longer in the HCA trial (p<0.05; Fig. 5).

DISCUSSION

The aim of the present study was to investigate the short-term ingestion of HCA on endurance exercise performance in untrained women, We tried to show in this study that whether or not the ingestion of 250mg HCA for 5d would increase fat oxidation and improve endurance performance.

Fig. 3, Carbohydrate (A) and fat (B) oxidation differ

ences during 40% VO2max cycle ergometer exercise.

Values are means•}SE.

HCA is an active ingredient that is extracted from the rind of the fruit Garnicia cabogia, a native species of India, HCA is a potent competitive inhibitor of the extramitochondrial enzyme ATP citrate-lyase (10), and also increases the rate of hepatic glycogen synthesis and decreases body weight gain (17).

Focused on body weight control, HCA ingestion for a period of months failed to result in the loss of body weight and body fat (7, 18). This is unlikely, since the conversion of citrate into acetyl-CoA by ATP citratelyase only occurs when energy intake exceeds the energy requirements of the body (19). It is well known that during low-to-moderate intensity exercise, more FFA are released from adipocytes into the blood than in resting condition. These FFA are re-esterified or used as an energy source during exercise. Therefore, when energy intake exceeds the energy needs in the active muscle, the conversion of citrate into acetyl-CoA occurs during exercise. Consequently, HCA would be an effective inhibitor of carbohydrate oxidation, especially during moderately intense exercise. Therefore, the effects of HCA ingestion might be emphasized with physical activity.

However, acute ingestion of HCA did not change fat oxidation during exercise or at rest (20). On the contrary, Ishihara et al. (11) reported that short-term ingestion of water-soluble type HCA, which we used in the present study, increased fat oxidation in trained mice. The physical conditions as to trained or untrained showed different energy metabolisms during exercise. Endurance exercise training reduces malonyl-CoA concentration (1), increases mitochondrial number (2) and

166 LIM K et al.

Fig. 4. Changes in blood glucose (A), lactate (B), and

FFA (C) concentrations during 40% VO2max cycle er

gometer exercise. Values are means•}SE.

mitochondrial uptake of long-chain fatty acids (3), and so on. Therefore, fatty acid oxidation increased and carbohydrate oxidation decreased during exercise of the same relative intensity for trained subjects.

Acute ingestion of HCA did not affect energy substrate utilization, especially in fat oxidation (7, 21). However, the short-term administration of HCA lowers RER and increases fat oxidation in trained subjects (13). In untrained subjects, HCA ingestion significantly decreased RER after 30min of exercise as shown in the present study (Fig. 2P). However, the effects were lower than those of trained subjects (12, 13), because training might enhance the fat oxidation rate. Our experiment was designed to test two different exercise intensities, 40% and 60% VO2max. These two intensities showed the effects of glycogen sparing during prolonged endurance exercise performance. The fat oxidation rate during the latter stage of exercise increased in trained subjects (13) and increased slightly in untrained subjects in the present study (data not shown).

In the present study, blood glucose and lactate con

Fig. 5. Exercise time to exhaustion at 60% VO2max af

ter 40% VO2max for 60min during the exercise . Val

ues are means•}SE. * Statistically significant from the

values of the placebo trial (p<0.05).

centrations during the former stage of cycle ergometer exercise were not significantly affected by HCA ingestion (Fig. 4). However, Van Loon et al, (20) reported that the lactate concentration was decreased by acute ingestion of HCA during exercise, although not significantly, as in the present study. These findings suggest that short-term ingestion of HCA might delay the lactate threshold since HCA has an inhibiting effect on carbohydrate oxidation (11, 13). Plasma FFA concentrations were not significantly affected by HCA ingestion. Considering the characteristics of HCA, it dose not have a lipolysis effect, which increaes FFA concentration as Ishihara et al. (11) reported. They suggested that the acute ingestion of HCA increases serum FFA concentrations in resting mice.

The enhancement of fat oxidation during exercise could lead to increased endurance exercise performance. In the present study, the cycle ergometer exercise time to exhaustion after 1h of 40% VO2max exercise was significantly enhanced by HCA ingestion . The increased fat oxidation with HCA ingestion may be attributed to the modification of CPT-I (carnitine palmitoyltransferase-I) activity (19); malonyl-CoA inhibits CPT-I activity in the cytosol, but its effect is suppressed by HCA as described above even in untrained state .

In summary, the short-term ingestion of HCA enhanced fatty acid utilization during moderately intense exercise in untrained women . Depressed energy utilization of carbohydrates by HCA during the former stage of exercise became important for keeping the energy source during the latter stage of high-intensity exercise in untrained subjects as observed in the trained subjects, Therefore, HCA ingestion (250mg per day) at least 5d before exercise can be considered an effective nutritional ergogenic aid for untrained people before

participating in some types of exercise activities.

AcknowledgmentsThe authors gratefully thank the students of the

Department of Sports Medicine, Kyung-Hee University, for their participation as subjects, and note special thanks to Hwang-Woon Mun for his technical assis

HCA Ingestion on Fat Oxidation in Untrained Women 167

tance in the exercise program. This paper was partly

supported by a research grant from Konkuk University

in 1999.

REFERENCES

1) Hutber CA, Rasmussen BB, Winder WW 1997. Endurance training attenuates the decrease in skeletal muscle malonyl-CoA with exercise. J Appl Physiol 83: 1917-1922.

2) Constable SH, Favier RJ, McLane JA, Fell RD, Chen D, Holloszy JO. 1987. Energy metabolism in contracting rat skeletal muscle: adaptation to exercise training. Am J Physiol 253: C316-C322.

3) Sidossis LS, Gastaldelli A, Klein S, Wolfe RR. 1997. Regulation of plasma fatty acid oxidation during low- and high-intensity exercise. Am J Physiol 272: E1065

-E1070.4) Kiens B, Kristiansen S, Jensen P, Richter EA, Turcotte LP.

1997. Membrane associated fatty acid binding protein (FABPpm) in human skeletal muscle is increased by endurance training. Biochem Biophys Res Common 231: 463-465.

5) Ryu S, Choi S-K, Joung S-S, Suh H, Cha Y-S, Lee 5, Lim, K. 2001. Caffeine as a lipolytic food component increases endurance performance in rats and athletes. J Nutr Sci Vitaminol 47: 139-146.

6) Graham TE, Spriet LL. 1991. Performance and metabolic responses to a high caffeine dose during prolonged exercise. J Appl Physi of 71: 2292-2298.

7) Heymsfield SB, Allison DB, Vasselli JR, Pietrobelli, Greenfield D, Nunez C. 1999. Garcinia cambogi for weight loss. JAMA. 282: 233-235.

8) Westerterp-Plantenga MS, Kovacs EM 2002. The effect of (-)-hydroxycitrate on energy intake and satiety in overweight humans, lot J Obes Relat Metab Disord 26:

870-872.9) Sullivan AC, Tricari J, Neal M. 1973. The influence of

(-)-hydroxycitrate on in vivo rates of hepatic gluconeogenesis: lipogenesis and cholesterol-genesis. Fed Proc 33: 556.

10) Watson JA, Lowenstein JM. 1970. Citrate and the conversion of carbohydrate into fat. J Biol Chem 245: 5993-6002.

11) Ishihara K, Oyaizu S, Onuki K, Lim K, Fushiki T. 2000. Chronic (-)-hydroxycitrate administration spares car

bohydrate utilization and promotes lipid oxidation during exercise in mice. J Nutr 130: 2990-2995.

12) Kim K-H, Kwon T, Ryu S, Suh H, Lee K-W, Lee S, Oishi Y, Tomi H, Lee K-C, Lee S-K, Yun S-J, Lim K. 2001. Effects of HCA ingestion on expired gas metabolism during endurance exercise, Kor J Exerc Nutr 5(1): 115-123.

13) Lim K, Ryu S, Ohishi Y, Tomi H, Suh H, Lee W-K, Kwon T. 2002. Short-term (-)-hydroxycitrate ingestion increases fat oxidation during exercise in athletes. J Nutr Sci Vitaminol 48: 128-133.

14) Lim K, Yoshioka M, Kikuzato 5, Kiyonaga A, Tanaka H, Shindo M, Suzuki M. 1997. Dietary red pepper ingestion increases carbohydrate oxidation at rest and during

exercise in runners. Med Sci Sports Exerc 29: 355-361.15) Loe YC, Bergeron N, Rodriguez N, Chwarz J. 2001. Gas

chromatography/mass spectrometry method to quanitify blood hydroxycitrate concentration. Anal Biochem

292: 148-154.16) Angus DJ, Hargreaves M, Dancey J, Febbraio M. 2000.

Effect of carbohydrate or carbohydrate plus mediumchain triglyceride ingestion on cycling time trial performance. J Appl Physiol 88: 113-119.

17) Lowenstein JM. 1971. Effect of (-)-hydroxycitrate on fatty acid synthesis by rat liver in viva. J Biol Chem 246: 629-632.

18) Heymsfield SB, Allison DB, Vasselli JR, Pietrobelli A, Greenfield D, Nunez C. 1998. Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial. JAMA 280: 1596-1600.

19) Kovacs EM, Westerterp-Plantenga MS, de Vries M, Brouns F, Saris WH. 2001. Effects of 2-week ingestion of (-)-hydroxycitrate and (-)-hydroxycitrate combined

with medium-chain triglycerides on satiety and food intake. Physiol Behav 74: 543-549.

20) Van Loon LJ, Van Rooijen JJ, Niesen B, Verhagen H, Saris WH, Wagenmakers AJ. 2000. Effects of acute (-)

- hydroxycitrate supplementation on substrate metabo lism at rest and during exercise in humans. Am J Clin Nutr 72: 1445-1450.

21) Kriketos AD, Thompson HR, Greene H, Hill JO. 1999. (-)-Hydroxycitric acid does not affect energy expenditure and substrate oxidation in adult males in a postabsorptive state. Iot J Obes Relat Metab Disord 23: 867

-873.