No medicinal herb contains a sufficient level of dietary nutrition to cause immediate weight gain. However, many herbal medicines contain compounds that stimulate the appetite and improve digestion in people who have difficulty gaining weight. If you have experienced a sudden decrease in weight or appetite, it is important to consult a qualified health care provider to determine the underlying cause. Do not use any medicinal herbs without first consulting a health care provider, particularly if you have a medical condition.
Cannabis, also known as marijuana, is one of the most effective natural methods for improving appetite. The medical marijuana information website Show Me the Facts lists dozens of well-designed, peer-reviewed studies confirming the efficacy of cannabis as an appetite stimulant.
In the United States, cannabis is only available for medicinal use in certain states, and it requires a prescription to obtain legally. A health care provider may prescribe medical cannabis as a treatment option for weight loss associated with anorexia nervosa, HIV, cancer or psychiatric disturbances.
A relative of the ragweed plant, the medicinal herb chamomile may act as a gentle appetite stimulant. The National Institutes of Health notes chamomile's traditional use as a digestive aid and a treatment for anxiety. Additionally, the organization suggests that it may improve mood, appetite and overall quality of life in cancer patients.
There is insufficient evidence to support the use of chamomile as a sole treatment option for any disease. However, it may be a viable option for people suffering from unwanted weight loss, particularly when it relates to stress or anxiety.
The National Institutes of Health reports that blessed thistle has been used historically in "bitter" tonics designed to improve digestion and enhance the appetite. Traditionally, healers have used these tonics for people who have difficulty gaining weight or eating sufficient quantities of food.
While noting blessed thistle's theoretical ability to treat anorexia and stimulate the appetite, the National Institutes of Health states that there is not enough evidence to support these uses. Nevertheless, because the herb has a low incidence of serious side effects, it may be worth a try as a complementary treatment option.