Caffeine and slimming
There are many studies that document the slimming effects of caffeine. Unfortunately, most of these studies used slimming mixtures that contained caffeine in combination with compounds such as ephedrine or green tea extract.
This makes it difficult to judge how much of the observed weight loss was due to caffeine and how much was due to one of the other ingredients. Some researchers do maintain that "high caffeine intake was associated with thermogenesis and fat oxidation and with suppressed leptin in women." (Westerterp-Platenga & coworkers, 2005).
In this Dutch study, the subjects received 150mg of caffeine per day. This indicates that increasing caffeine intake to 150mg per day may assist with weight loss.
If you keep in mind the table of caffeine contents published in the first of these articles on caffeine, then anyone drinking three cups of tea, or four cups of instant coffee, would ingest 150mg of caffeine a day, which may promote slimming.
Readers should not, however, increase their coffee and tea intake to absurd levels like 10 cups a day to promote weight loss. Excessive caffeine intake may cause pronounced side effects like palpitations, insomnia, irritability etc.
Drink tea or coffee in moderate quantities when you are trying to lose weight, but keep in mind that you also need to reduce your energy intake with a sensible, balanced, low-energy diet, and increase your energy output by doing daily exercise for at least 30 minutes or more per day.
Caffeine and athletic performance
The following physiological effects of caffeine may enhance athletic performance:
- stimulation of the central nervous system, which leads to reduced perception of effort (reduced fatigue), or enhanced use of muscles;
- stimulation of the heart muscle;
- stimulation of diuresis (excretion of water by the kidneys);
- stimulation of the release of epinephrine by the body (the "fight-or-flight" hormone), which releases fats for muscle activity.
In view of the above, caffeine has been used for many years by sportsmen and women to enhance their performance, prevent fatigue and give athletes a "lift".
In 1994, the International Olympic Committee (IOC) banned the use of caffeine by athletes as a performance-enhancing drug. Athletes with urine samples in which the caffeine content exceeded 12 micrograms per litre were regarded as "caffeine doped".
Research indicates that intakes of caffeine exceeding 9mg/kg of body weight (e.g. a 70kg athlete ingesting more than 630mg of caffeine per day) do not increase athletic performance more than having about 6mg/kg of body weight (e.g. the 70kg athlete would only have to ingest 420mg of caffeine per day).
The optimal dose for improving athletic performance according to Burke and Deakin (2000) is, therefore, 5-6mg/kg body weight.
These authors point out that increasing caffeine intake above this level will not provide any further benefits. Too high a caffeine intake by sportsmen and women can cause negative side effects such as the shakes, palpitations, headaches etc. It may also cause dehydration.
It has been found that some athletes do not respond to caffeine stimulation by increasing their performance, so you need to experiment before a big event to see if caffeine supplementation does improve your performance or not.
Previously it was recommended that athletes should have their caffeine one hour before the event, but more recent research indicates that some athletes may require modest doses throughout the event. Further research will hopefully clarify this question of the timing of caffeine intake.
Now that the World Anti-Doping Agency (WADA) has lifted its ban on caffeine as a performance-enhancing drug in sport in 2004, athletes can make use of caffeine in moderation to improve their performance (provided of course that they are 'responders' to caffeine).
Other factors that may influence how athletes respond to the performance-enhancing effects of caffeine include:
- type of exercise – there are indications that cyclists may respond better than runners;
- well-trained athletes may respond better than poorly trained ones;
- the habitual caffeine intake of an athlete may also play a role;
- the dietary status of the athlete may influence how he or she responds to caffeine;
- women and men may respond differently to caffeine.
So, you clearly need to test how you will respond to caffeine before you use it in a big event.
Danger of dehydration
Caffeine stimulates diuresis or excretion of water by the kidneys. Athletes who drink cola drinks during events may find that the caffeine they ingest leads to dehydration.
It is, therefore, important that athletes, especially those competing in hot climates or in very long events, should ensure good hydration by drinking sufficient water or energy drinks in addition to cola drinks.
It may be prudent to use small amounts of caffeine to stimulate athletic performance, but concentrate on proper hydration and supply of energy by primarily using energy drinks and some water during long, hot events.
After an event, caffeine-containing drinks are not regarded as ideal rehydration drinks and it is better to use sports drinks, and commercial oral rehydration solutions to replenish the water that was lost during exertion (Burke & Deakin, 2000).
Caffeine is a stimulant that can cause a number of physiological effects, which can be used to promote slimming and enhance athletic performance. It should, however, not be used in excessive quantities (e.g. more than 300mg/day for everyday use and 420mg/day to enhance athletic performance in responsive athletes).
Always keep in mind that as a stimulant, caffeine can cause negative side effects, but that moderate intakes of caffeine should not cause problems for most people. – (Dr Ingrid van Heerden, DietDoc)
Reference: (Burke & Deakin (2000). Clinical Sports Nutrition, 2nd Ed,. McGraw-Hill Co, Australia; Westerterp-Platenga et al (2005). Body weight loss & weight maintenance in relation to habitual caffeine intake & green tea supplementation. Obesity Research ,13(7):1195-204.)