Caffeine is a stimulant that is often used by dieters because it increases thermogenesis (heat generation due to the bodies metabolism). Studies suggest that moderate caffeine intake can increase daily calorie expenditure by more than 100 calories a day.
One study, published in the American Journal of Clinical Nutrition, looked at the effect of caffeine on total energy expenditure in a group of lean and obese women. The researchers found that 100mg of caffeine increased energy output by 3 to 4% over a 150 minute period. When the caffeine was administered at two hour intervals during a 12 hour period, total energy intake was increased by 12% in the lean group and 8% in the obese group. This equated to around 150 additional calories burned per day in the lean group and 80 calories in the obese group.
The thermogenetic effect of caffeine appears to increase linearly with the size of the caffeine dose meaning a 200mg dose of caffeine leads to twice the thermogenetic effect of a 100mg dose. Caffeine has a relatively short half life of 3-4 hours (the amount of time required for the body to metabolize half the caffeine) meaning caffeine needs to be consumed at regular intervals for the thermogenetic effects to continue throughout the day.
A pound of fat contains 3,500 calories so 200mg of caffeine consumed three to four times during the day equates to around three additional pounds of fat lost every month.
Caffeine is well tolerated by the body meaning it can be consumed in relatively high amounts with no significant long tern effects on the body. Caffeine does increase blood pressure levels and there is some concern that long term use of caffeine can increase the risk of heart disease however this is not supported by the majority of scientific studies. One of the largest studies on the effects of caffeine on heart disease involved over 40,000 men and 80,000 women from the Health Professionals Follow-Up Study (HFPS). The researchers found no association between caffeine intake and heart disease with those in the highest quartile for caffeine intake actually at a slightly lower risk of heart disease compared to those in the lowest quartile for caffeine intake.
Regular strength 100mg caffeine supplements and “extra strength” 200mg supplements are available at most health stores and pharmacies. A standard cup of coffee normally contains between 80 and 120mg of caffeine. A cup of tea contains 50mg of caffeine, a can of coca cola contains 35mg of caffeine and 100 grams of dark chocolate contains around 70mg of caffeine.