Your brain craves bad carbs, study finds

New brain studies suggest that carb addiction could be real.

Boston Children’s Hospital researchers who scanned the brains of men after they drank milkshakes containing rapidly digesting, highly processed carbohydrates found the men experienced a surge in blood sugar followed by a sharp and sudden crash four hours later. That plummet in blood sugar activated a powerful hunger signal and stimulated the brain region that is considered ground zero for addictive behaviour.

“We showed for the first time that refined carbohydrates can trigger food cravings many hours later, not through psychological mechanisms — a favourite food is just so tasty, you need to keep eating — but through biological effects” on the brain, said lead author Dr. David Ludwig.

The study was small and focused exclusively on men. As well, the notion of food addiction is highly controversial and “vigorously debated,” the team writes. Still, the findings suggest limiting foods high in highly processed, “high glycemic index” carbs such as white breads, white rice, potatoes and concentrated sugars could help overweight and obese people control the urge to overeat, they said.

Ludwig’s team performed functional MRI brain scans — machines that capture the brain at work in real-time — on 12 overweight or obese men aged 18 to 35 after they consumed two liquid test meals that looked and tasted identical, and contained the same amounts of calories and carbohydrates.

The only difference was that one shake contained fast-digesting, high-GI carbs, the other slow-digesting carbs.

After the high GI liquid meal, blood sugar surged initially, but crashed four hours later. The men not only reported greater hunger, their MRI scans also showed intense activation in the nucleus accumbens, the part of the brain involved in reward and craving.