How you get the munchies is zol down to hormones
Scientists get to the bottom of how our brains switch to 'hungry mode' after a joint
The munchies might finally have a meaning.
After dosing laboratory rats with dagga vapour, scientists have worked out how the drug triggers hunger hormones.
The Washington State University team also identified regions of the brain that shift to “hungry” mode while under the influence, and hope their findings will lead to new treatments for illness-induced anorexia.
They presented their research this week at the 26th annual meeting of the Society for the Study of Ingestive Behavior in Florida, US, where a torrent of research from eating experts tackled 21st-century health problems such as obesity, Type 2 diabetes and drug addiction.
Oddly, it was an addictive drug (dagga) that was targeted by the Washington team because of one of its side-effects: hunger, or “the munchies”.
Severe appetite loss is a common symptom of many chronic illnesses and is especially problematic in cancer, HIV/Aids, heart disease and some metabolic disorders.The team set out to see how they could produce the munchies in patients struggling with these conditions, while avoiding dagga’s less desirable effects on the mind and body.
“We all know cannabis use affects appetite, but until recently we’ve actually understood very little about how or why,” said researcher Jon Davis. “By studying exposure to cannabis plant matter, the most widely consumed form, we’re finding genetic and physiological events in the body that allow cannabis to turn eating behaviour on or off.”
Brief exposure to cannabis vapour stimulated a meal even when rats had recently eaten, suggesting that inhaling cannabis tricks appetite circuits in the brain into hunger mode.
“We found that cannabis exposure caused more frequent, small meals,” said Davis. “But there’s a delay before it takes effect.”
The delay provided a clue to how the drug may act. When the stomach is empty, it releases a hormone called ghrelin to tell the brain it’s time to eat – and Davis’s team found cannabis triggered a ghrelin surge. When they gave a second drug that prevented the ghrelin surge, cannabis no longer triggered eating.
They also found changes in how the brain responds to the message. In a small region of the hypothalamus responsible for sensing ghrelin, cannabis changed the genetic activity of brain cells that respond to the hormone.In other research tabled at the conference:
• Ghrelin was also implicated in drug and alcohol addiction, according to Lorenzo Leggio, leader of a joint team from the National Institute on Alcohol Abuse and Alcoholism and the National Institute on Drug Abuse in the US. Leggio, one of the panellists discussing data from animal experiments and preliminary trials in humans, said the gut hormone system was a prime target for novel anti-addiction treatments.
• A team from the University of Tübingen in Germany said a simple instruction to change your thinking as mealtime approaches can help cut calories. They asked study participants to think about either the health effects of food, expected pleasure, or their intention to stay full until dinner time while choosing their portion size for lunch. Participants in all weight categories selected smaller portions when prompted to think about health.
• Scientists at Rutgers Brain Health Institute in the US said a small group of brain cells in the hypothalamus could be a promising target for medications to control binge-eating in obese people. The same neurons have previously been shown to be important for addiction to several drugs, including cocaine. When they blocked the signals to the calls using medication, rats with unlimited access to sweet, fatty treats ate less.
• University of Wyoming pharmacists said a new drug based on capsaicin (the compound that gives chillies their spice) caused long-term weight loss and improved metabolic health in mice eating a high-fat diet. “We observed marked improvements in blood sugar and cholesterol levels, insulin response and symptoms of fatty liver disease,” said lead investigator Baskaran Thyagarajan. Mice in the experiment remained on the drug for eight months, maintaining the weight loss with no evidence of safety problems. Thyagarajan said the drug looked like being “a potent anti-obesity treatment”.
• A team from the University of Pennsylvania and Syracuse University said that by modifying the key ingredient in drugs used to treat Type 2 diabetes, they had eliminated side-effects such as nausea and vomiting. The researchers modified the active ingredient in the drugs so that it is less easily absorbed into regions of the brain that trigger nausea and vomiting. Type 2 diabetes occurs when the body stops responding properly to insulin, resulting in chronically high blood sugar. It is most common in people who are overweight or obese.