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What is Caffeine?  Caffeine is the active substance (a methylxanthine) found in tea, coffee and guarana. Caffeine has long been considered an ergogenic aid capable of improving physical performance.  It works by activating the central nervous system and sympathetic nervous system.  This has led to the International Olympic Committee (IOC) setting an upper limit for the legal use of caffeine during competition.  The present IOC legal limit is a urine concentration of 12µgml of caffeine.  A person weighing 70kg may have to consume 5 or more cups of coffee to reach the banned level of caffeine consumption.  Consumption of 2-3cups of coffee 1-2hours before competition would not result in a positive doping offence.


Who might benefit from Caffeine supplements?  Because of the positive effect that caffeine has on fat metabolism, endurance athletes can use it to enhance endurance race performance.  Caffeine may also prove beneficial during short intense efforts such as weight training, however research has been, generally, inconclusive as to whether caffeine is beneficial to strength/power athletes.  It should be noted that caffeine consumption is best reserved for competition since prolonged use reduces the beneficial effects of caffeine. Because caffeine acts as a potent thermogenic (fat burner) it may also prove useful for weight loss.


Summary of Caffeine's physiological effects:

  • Enhanced endurance exercise performance

  • Enhanced sprint/short-term exercise performance

  • Enhanced metabolic rate

  • Increased rate of fat metabolism

  • Enhanced fat loss

  • Improved mental function


What does research say about Caffeine?  Research has demonstrated that caffeine, when given at a dose below the current IOC legal limit, improves 1500m run performance by approximately 4.2secs (Wiles et al.,1992) as well as long term endurance performance (Costil et al., 1977; Costil et al., 1978; Ivy, 1979; McNaughton, 1987).  The improved endurance performance is due primarily to a significant increase in the level of free fatty acids in blood plasma (Bucci, 1993).  The increased levels of free fatty acids in the blood would enhance the ability to use free fatty acids as fuel, and thus spares valuable carbohydrate stores.  It should be noted that greater benefits are achieved if you are unaccustomed to consuming caffeine products (Spriet, 1995).  

Caffeine is believed to work by: 1) activating the central and sympathetic nervous system; 2) improving excitation of active muscle; 3) increasing the secretion of catecholamines (stress hormones which increase the release of free fatty acids in the blood); 4) by stimulating an increase in the rate of fat metabolism which helps to preserve the glycogen stores, and; 5) by increase in potassium accumulation in the blood. 

Research has also demonstrated that caffeine can enhance performance during short term, high intensity exercise (Doherty, 1998) and therefore may be beneficial for strength/power athletes as well as endurance athletes. 

Because caffeine enhances fat burning, within our body, there has been much interest into whether it may promote fat loss.  Research has shown that caffeine consumption before exercise enhances fat burning during exercise by around 30% (Spriet, 1995) as well as increasing the amount of calories burned after exercise (Chad and Quigley, 1989). 


Is Caffeine effective?  Research has demonstrated that caffeine is effective at enhancing both endurance and short term exercise performance.  It can also enhance mental abilities, such as mental focus and reaction time, and is a potent thermogenic that increases fat burning and may aid weight loss.  However, some people can suffer negative side effects such as heart palpitations and nervousness.


How should I take Caffeine?  Firstly, it is important to note that you will not gain the same benefits from the consumption of coffee as from taking a caffeine supplement.  The reason for this appears to be due to another, as yet unknown substance, within coffee, that inhibits the positive effects of caffeine.  A general recommendation to improve endurance, or power, performance would be to consume 150-200mg of caffeine 30-60 minutes prior to competition – this will not result in a positive doping result (unless you weigh less than 35kg!).  It should be noted that athletes who regularly consume large quantities of caffeine will gain less of a benefit from its consumption due to a decreased physiological response.  Also some athletes may suffer with increased anxiety levels following caffeine supplementation and therefore, for those athletes, any positive effect may be outweighed by the negative effects.  Therefore athletes intending on using caffeine for an important race should check their response to caffeine in a training situation before using it in competition.   

For weight loss, consider using 150-200 milligrams every 4-5 hours.  For, best results combine with regular exercise (at least 3 times per week).  Don’t consume high levels of caffeine for more then 2-3 weeks at a time.  Long term caffeine use should be avoided since caffeine consumption causes an increase in the levels of stress hormones.  Long term exposure to high stress hormone levels will leave you feeling drained and run down.  If you combine this with heavy training you put yourself at risk of over-training.   



Bucci, L. (1993) Nutrients as ergogenic aids for sports and exercise. Boca Raton, FL:CRC Press. 

Chad, K. and Quigley, B. (1989) The effects of substrate utilisation, manipulated by caffeine, on post-exercise oxygen consumption in untrained female subjects.  European Journal of Applied Physiology. 59, 48-54. 

Costill, D. L., Coyle, E. F., Dalsky, G., Evans, W., Fink, W. and Hoopes, D. (1977) Effects of elevated plasma  FFA and insulin on muscle glycogen usage during exercise. Journal of Applied Physiology. 43, 695-699. 

Costill, D. L., Dalsky, G. P. and Fink, W. J. (1978) Effects of caffeine ingestion on metabolism and exercise performance. Medicine and Science in Sport and Exercise. 10, 155-158. 

Doherty, M. (1998) The effects of caffeine on maximal accumulated oxygen deficit and short-term running performance. International Journal of Sport Nutrition. 8, 95-104. 

Ivy, J. L., Costill, D. L., Fink, W. J. and  Lower,  R. W. (1979) Influence of caffeine and carbohydrate feeding on endurance performance. Medicine and Science in Sports and Exercise. 11, 6-11. 

McNaughton, L. (1987) Two levels of caffeine ingestion on blood lactate and free fatty acid responses during incremental exercise. Research Quarterly in Exercise and Sport. 58, 255-259. 

Spriet, L. L. (1995) Caffeine and performance. International Jounal of Sport Nutrition. 5, S84-99. 

Wiles, J. D., Bird, S. R., Hopkins, B. A. and Riley, B. A. (1992) Effect of caffeinated coffee on running speed, respiratory factors, blood lactate and perceived exertion during 1500-m treadmill running. British Journal of Sports Medicine. 26 (2), 116-120.

Although, every attempt is made to ensure the accuracy of the information on this site, the publisher does not accept responsibility for the accuracy of information on this site. This material is not intended for use to diagnose, treat, cure, or prevent any disease.  The publisher does not accept any responsibility for consequences that may arise through the consumption of any supplement or nutritional product discussed on this site. You should always consult a physician, doctor, nurse, pharmacist or health practitioner before consuming any nutritional supplement.  Always read the product label and be aware of any possible side-effects or possible drug interactions before taking any nutritional product.

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Last modified: 01/05/06