Guarana is common to many popular stimulant-based weight loss products (like Estrin-D and the popular Lean System 7, one of the few products which we recommend). Guarana is included mainly for its caffeine content (caffeine is a potent thermogenic, and guarana is standardized to between 10-16% caffeine), but guarana has other potential benefits…
It also has antioxidant and diuretic properties. Harvested in Brazil and Uraguay, this wild-growing climbing shrub has been used for centuries as a general health-tonic, and recently as a refreshing, “invigorating” drink. However, it’s the fat burning potential of guarana that concerns us most here. When harvested and processed, the ripe Guarana fruit yields about 10% caffeine.
Caffeine does a fine job of goading the nervous system into action, resulting in additional fat burning through a complex process called lipolysis (encourages fat cells to release fat into the bloodstream for fuel). It also provides a decent energy boost that spurs performance.
For this reason, it is also being added to many performance drinks — although many consumers are unaware that guarana is standardized for caffeine.
And yes, there is clinical data validating caffeine’s effects on weight loss (see Am J Clin Nutr. 1989 Jan;49(1):44-50, Am J Clin Nutr. 1980 May;33(5):989-97, Am J Physiol. 1995 Oct;269(4 Pt 1):E671-8).
As an ancillary ingredient, guarana does provide some value to most compilations — although its effects are not dramatic by any means. In other words, I would not be scared away by any product that uses guarana in a back-up role.
Any product that uses guarana as a core ingredient (like Brazlian Phyre) should be avoided, because there is little evidence guarana provides much of a fat burning effect beyond that of its caffeine content.