Yerba Mate, Ilex paraguariensis, is grown in several countries in South America. Leaves of Yerba Mate (Pic 1) are used to make medicine. It is claimed to promote overall health, wellness and stable energy. It is also used as a stimulant to improve mood and depression, to relieve fatigue and can be found in many fat burning supplement (probably as alternate source of caffeine). Yerba mate contains three xanthines (mild stimulants): theophylline (1,3-dimethylxanthine), theobromine (3,7-dimethylxanthine), and caffeine (1,3,7-trimethylxanthine) .
Yerba Mate for Weight Management and Obesity
Extracts of yerba mate are frequently found in herbal weight-loss dietary supplements. Because yerba mate has been suggested in the management of obesity, Demétrius and others  evaluated the effects of yerba mate extract on weight loss and obesity-related biochemical parameters. After 12 weeks on a high-fat diet mice that received 1.0 g/kg of yerba mate extract exhibited marked reduction in weight gain, adiposity, and restoration of the serum levels of cholesterol, triglycerides, LDL cholesterol, and glucose . Therefore, their data showed that yerba mate extract has potent anti-obesity activity in vivo .
Pic 1: Yerba Mate (Ilex paraguariensis) plant
Mixed combinations of herbs such as yerba mate, guarana and damiana also show benefits for weight management. 44 healthy overweight patients that received mix of these three herbs exhibited significantly delayed gastric emptying, reduced the time to perceived gastric fullness and induced significant weight loss over 45 days compared to placebo .
Other Yerba Mate Benefits
LDL-cholesterol Lowering Properties
Yerba mate also shows promise for cholesterol management. One hundred and two subjects participated in a single-blind controlled trial who were given roasted yerba mate infusion for 40 days. The results clearly showed that yerba
mate infusion significantly improved serum lipid parameters. Yerba mate consumption reduced LDL-cholesterol by 8.7% (p < 0.05) for subjects with the normal amount of lipids in the blood and further 10.0 and 13.1% reduction in LDL-cholesterol after 20 and 40 days, respectively (p < 0.001) for hypercholesterolemic individuals.  According to this, Yerba mate may reduce the risk for cardiovascular diseases.
Stimulant and Diuretic
According to some studies Yerba mate is also used as a stimulant and diuretic (probably due to its xanthines content) . However, compared to other stimulants such as caffeine and some teas there are a few scientific reports relating to Yerba mate.
Rosana Filip and others  evaluated antioxidant activity of Ilex family and reported the highest antioxidant activity for Ilex Paraguariensis (Yerba mate). Researchers also speculated that regular consumption of yerba mate beverage may significantly improve human antioxidant defense.
Yerba Mate Side Effects
Due to Yerba mate’s caffeine content there are also common side effects: palpitations, gastrointestinal disturbances, anxiety, increased blood pressure and insomnia . The only double-blind randomized clinical trial did not report on adverse events .
Athayde, Margareth Linde, Geraldo Ceni Coelho, and Eloir Paulo Schenkel. “Caffeine and theobromine in epicuticular wax of Ilex paraguariensis A. St.-Hil.” Phytochemistry 55.7 (2000): 853-857.
Arçari, Demétrius P., et al. “Antiobesity effects of yerba maté extract (Ilex paraguariensis) in high-fat diet–induced obese mice.” Obesity 17.12 (2009): 2127-2133.
Andersen, T., and J. Fogh. “Weight loss and delayed gastric emptying following a South American herbal preparation in overweight patients.” Journal of Human Nutrition and Dietetics 14.3 (2001): 243-250.
de Morais, Elayne C., et al. “Consumption of yerba mate (Ilex paraguariensis) improves serum lipid parameters in healthy dyslipidemic subjects and provides an additional LDL-cholesterol reduction in individuals on statin therapy.” Journal of agricultural and food chemistry 57.18 (2009): 8316-8324.
Heck, C. I., and E. Gonzalez De Mejia. “Yerba Mate Tea (Ilex paraguariensis): a comprehensive review on chemistry, health implications, and technological considerations.” Journal of Food Science 72.9 (2007): R138-R151.
Filip, Rosana, et al. “Antioxidant activity of Ilex paraguariensis and related species.” Nutrition research 20.10 (2000): 1437-1446.
Bastos, Deborah Helena Markowicz, et al. “Yerba mate: pharmacological properties, research and biotechnology.” Med Aromat Plant Sci Biotechnol 1.1 (2007): 37-46.