Guarana (Paullinia cupana) is a plant whose seeds naturally contain caffeine; it is an ingredient in some weight-loss supplements. Any weight-loss effect comes mainly from its caffeine, and ODS says trials of caffeine for weight loss have all been short and used combination products.
Also known as: Paullinia cupana.
The one guarana weight-loss trial ODS describes used a blend of 336 mg yerba mate, 285 mg guarana (3% to 6% caffeine) and 108 mg damiana before each main meal for 45 days (ODS, Andersen 2001). For healthy adults, FDA and EFSA say up to 400 mg of caffeine a day from all sources does not pose safety concerns (ODS). These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
Hidden caffeine: ODS says some weight-loss supplement labels list herbs such as guarana without stating how much caffeine the product contains, so people may not know they are taking caffeine and possibly other stimulants.
What studies show: ODS says caffeine increases energy use and fat burning, but how much this affects weight is less clear, and regular use leads to tolerance. In a 45-day trial in 47 adults with overweight, a blend of yerba mate, guarana and damiana taken before meals led to 5.1 kg of weight loss versus 0.3 kg on placebo, and it slowed stomach emptying (ODS, Andersen 2001). Because the product had three herbs, the trial cannot show what guarana did on its own.
Safety: caffeine can cause trouble sleeping, nervousness, jitteriness and shakiness. ODS says caffeine can be toxic at 15 mg per kg (about 1,000 mg for a 150-lb adult), causing nausea, vomiting, fast heart rate and seizures, and combining caffeine with other stimulants such as bitter orange or ephedrine can make these effects stronger. FDA and EFSA have not set a safe intake for children. FDA warns that many products sold for weight loss, including supplements and teas, are likely to contain dangerous hidden drug ingredients, and that its public list of such products covers only a small fraction of them.
We do not list a guarana-specific figure. Its stimulant effect comes from caffeine, which ODS says has a half-life of about 6 hours, with blood levels peaking around 60 minutes after intake; how fast a guarana product releases its caffeine is not something we could confirm.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator