Three ingredients in Fit Tea contain caffeine, side effects of which may include irritability, sleeplessness and diarrhea. Higher doses of caffeine may worsen pre-existing conditions such as depression, panic disorder and premenstrual syndrome, states Drugs.com.
The caffeinated ingredients in Fit Tea are oolong tea, green tea and guarana. Guarana contains up to 3.6 to 5.8 percent caffeine by weight, a higher concentration of caffeine than is typically found in coffee, states WebMD. While guarana is popular in weight loss supplements, as of March 2015, no studies have proven it has an impact on weight beyond that of caffeine by itself.
Green tea contains a comparable amount of caffeine, but may have positive effects such as reduced inflammation and a slowing of joint degeneration, explains WebMD. Green and oolong teas also contain fluoride in levels that may be beneficial for dental health.