The researchers investigated the impact of the caffeine from maté and found that it was a contributing component to mitigating weight in rats who were fed a high-fat, high-sugar diet.
They found that it specifically reduced fat tissue overall and regulated the further formation of fat cells. Rats who were given caffeine from maté saw 16% less weight gain and 22% less body fat accumulation than those fed simply a high-sugar diet. The caffeine did not have to exist in isolation for the rats to see benefits for weight maintenance: Researchers found that rats who consumed maté in its tea form also benefited.
Over a month, rats were fed a less-than-optimal diet and were given some form of caffeine. The researchers used caffeine from maté, decaf maté, caffeine from coffee, and fabricated caffeine. They hoped to establish what it is about maté that may be providing support for healthy weight, and it seems caffeine is critical to this benefit.