Today I am looking at the role of Caffeine as a fat burner and performance enhancing drug, its effects, side effects and doses. Caffeine is the most widely used stimulant drug in the world, often found in coffee, tea, soft-drinks, some non perscription medications and chocolate.

 In 1 January 2004, caffeine was removed from the 2004 World Anti-Doping Agency Prohibited List

Effects of Caffeine 

• Effects include the mobilisation of fats from adipose tissue and the muscle cells
• Alterations to the central nervous system to change perceptions of effort or fatigue
• Stimulation of the release and activity of adrenaline, and effects on heart.  

Caffeine enhances endurance performance because it promotes an increase in the utilisation of fat as an exercise fuel and 'spares' the use of the limited muscle stores of glycogen. studies now show that the effect of caffeine on 'glycogen sparing' during sub-maximal exercise is short-lived and inconsistent - not all athletes respond in this way.

The metabolic effect of caffeine are more variable in untrained people. 

There is evidence that caffeine enhances endurance and provides a small but worthwhile enhancement of performance over a range of exercises including short-duration high-intensity events (1-5 min), longer high-intensity events (20-60 min) and endurance events (90 min + continuous exercise).

Traditional protocols for the use of caffeine involve the intake of caffeine one hour prior to the event, in doses equivalent to  6 mg/kg

Newer studies in available literature suggests that performance benefits can be seen with moderate amounts 3 mg per kg of body mass of caffeine 1 hour prior to exercise. These studies show that performance benefits do not increase with increases in the caffeine dose above 3 mg/kg. The use of larger doses of caffeine increases the risk of side-effects.

Side Effects

small to moderate doses of caffeine have minor effects on urine losses or the overall hydration in people who are habitual caffeine users. Because caffeine increases the production of stomach acid it may worsen ulcer symptoms or cause acid reflux. Insomnia, poor sleep, and anxiety are well described psychological side effects of caffeine. At higher levels of intake, caffeine has the potential to cause increases in heart rate, impairments or alterations of fine motor control and technique.


At intakes above 13 mg/kg of bodymass the risk of side effects are significant


 Sudden discontinuation of caffeine in a regular user may trigger caffeine withdrawal symptoms. The most common symptoms are headache and fatigue.

References

Appl Physiol Nutr Metab. 2008 Dec;33(6):1319-34.
AIS Fact Sheet