Guarana switches on brown fat to restrict weight gain, researchers find

In the recent study, published in the journal ​Phytotherapy Research, the authors, who are associated with institutions in Puerto Alegre and Lagarto, Brazil and Barranquilla in Colombia, looked into whether guarana supplementation by itself could have these effects.  The researchers said the botanical has been studied before, but usually as a component of herbal blends.

Studying the botanical in isolation

The researchers said without studying guarana in isolation it was difficult to know with precision what it does and how safe it is. 

“It is worth noting that many adverse effects associated with guarana are generally observed in mixtures where guarana is only one active ingredient, and the toxic potential of guarana itself is unknown. In this regard, the effectiveness and toxicity of guarana seed powder (GSP) need to be further explored,”​ they wrote.

The researchers used a commercial seed powder from Lifar, a Brazilian company that sells supplements and other consumer packaged goods.  Lifar offers its guarana seed powder in capsules as well as in a bulk powder form.

The study design employed four groups of 12-week old Wistar rats.  One side of the study the rats ate a commercial low fat diet with and without 0.5% guarana seed supplementation, while on the other they ate a high fat simulated Western diet (WD), with and without supplementation.

The researchers looked in detail at the effects of four constituents of guarana: caffeine, theobromine, catechin, and epicatechin.  The study delved into the pharmacology of these compounds to parse out where they had their weight management effects.

Guarana didn’t suppress appetite, but still restricted weight gain

The study found that in the high fat group, the guarana supplementation restricted both weight gain and fat accumulation. The supplemented rats gained about 280 grams of body weight during the 16 week study, whereas the control, high fat group gained about 330. But the supplemented rats did not consume less food, indicating the appetite suppression effects popularly associated with these compounds—especially caffeine—may not be the true mode of action.

A weight gain suppression effect for guarana was also observed with the standard diet side of the study but was not as pronounced. The differences observed there were about 240 grams of weight gain for the control group eating a standard diet with no supplementation vs about 220 grams for the supplemented group.

The researchers also looked at insulin sensitivity among the rat groups. They found that guarana prevented high leptin levels in the serum of the WD rats, and prevented irregularity in the function of adiponectin (adiponectin is a protein hormone which is involved in regulating glucose levels as well as fatty acid breakdown).

“These results suggest that guarana treatment improved glucose homeostasis and adipokine deregulation,” ​they wrote.

Beefing up the brown fat

As a mode of action for these effects, the researchers postulated that guarana activated the brown adipose tissue (BAT) of the experimental group, both by increase the mass of this tissue and by fostering mitochondrial activity within it.  BAT has been shown to help mammals maintain body heat homeostasis​​; thus is a tissue that helps consume energy rather than primarily storing it, as is the case with white adipose tissue.

“An increase in BAT weight was observed only in the WD + Gua group compared with the control. In parallel, the BAT mitochondrial copy number was higher,”​ they wrote.

In addition to the anti-obesity effects observed, the researchers determined that the botanical was safe at the dosages they used.

In a cautionary statement to NutraIngredients-LATAM, lead author Rafael Calixto Bortolin said that the results, while promising, need to be followed up with studies in humans.

Source: ​Phytotherapy Research​​
Guarana supplementation attenuated obesity, insulin resistance, and adipokines dysregulation induced by a standardized human Western diet via brown adipose tissue activation ​
DOI: 10.1002/ptr.6330
Authors: Bortolin RC, et al.