TORONTO – Those cravings for chocolate bars, bowls of pasta and French fries – they’re powerful, and they’re real, Harvard scientists say in a new study.
The American study is suggesting that some foods can be triggers for addiction as much as drugs and alcohol. This is why it’s so hard to fight the desire for so-called bad carbs, Canadian doctors say.
“It’s absolutely real,” she said.
In the Harvard study published earlier this month, the researchers looked at food with a high glycemic index (GI) – that includes white bread, sugary cereals, potatoes or soda and beer.
They fed milkshakes to 12 overweight or obese men. There were two variations, but they had the same amount of calories, taste and sweetness – the only disparity was that one contained a high GI while the other was prepared with slowly disgesting carbohydrates or a low-glycemic index.
After they drank their meals, the scientists noted differences: those who drank the high-glycemic milkshakes had an initial surge in blood sugar levels followed by a sharp crash just hours later. That left them feeling hungry again.
MRI scans that took photos of brain activity revealed that the shakes even activated the nucleus accumbens, a critical region in the brain linked to addictive behaviours.
It’s a part of the limbic system or what’s dubbed as the reward centre of the brain.
“Beyond reward and craving, this part of the brain is also linked to substance abuse and dependence,” lead researcher, Dr. David Ludwig says.
Our thinking is overpowered in the limbic system region of our brains, Tarman explained.
“This is why people say, ‘I shouldn’t be doing this, this is stupid.’ This is the part of the brain that is more dominant than we’d like to think and that’s evident in addiction,” she said.
Tarman specializes in addiction, specifically drugs, at two rehabilitation centres in Toronto.
She said that when patients are weaned off of drugs in rehabilitation, they’ll snack on “cheerful food” like chocolate, fries, or other snacks. Within weeks, they’ve packed on the pounds.
In research, cocaine has been linked to a surge of excess dopamine. Similar results have been found in sugar, Tarman says.
After indulging in too much pasta or carbs, diners can feel sleepy, numb and relaxed – that’s serotonin kicking in, she suggests.
Dr. Ali Zenter, a Vancouver-based doctor specializing in obesity, said that the study shows that food has a place in the hedonic system as people turn to certain meals for pleasure.
“Hunger used to be regulated by a system in our body that was very primitive, judged by being hungry or full, caloric intake or time of day,” she said.
“Now, the average human being is exposed to over 600 food cues.”
Zenter doesn’t want to label the issue as “food addiction” because it is so broad.
“It implies a very black-and-white type of interpretation to something that isn’t so black-and-white. It shows us that food cravings aren’t in your head, there’s definite body chemistry,” she said.
Ludwig calls for limiting high-glycemic index carbohydrates to help overweight diners reduce their cravings and control the urge to overeat.
Tarman said stress or other challenging factors in life can test willpower and could lead back to old habits, but people can be taught how to stay away from their eating vices.
Zentner says that willpower can be practiced, too.
“It’s like a muscle. It fatigues like any other and gets stronger if you use it more,” she explained.
Ludwig’s findings add to a growing movement pointing to food addiction. It’s still a very contentious idea, though.
Tarman said that because it’s still so novel, research has been experimental and is slowly moving into clinical areas.
A Canadian study published in May suggested that sugary syrups widely used in processed food and drinks cause the same feel-good changes to the brain as cocaine.
In that case, the University of Guelph scientists found that rats had trouble with cravings and loss of control.
Harvard Medical School offers its own list of high-glycemic foods on its website here.