Tucking into a breakfast of buttermilk pancakes and maple syrup, or a great bowl of white pasta for lunch, not only sends your blood sugar soaring — and then, suddenly, plummeting. Four hours after you’ve put down your fork, such a meal makes you hungrier than if you’d eaten one with more protein and fiber and fewer carbohydrates, a new study finds.
The study also demonstrates that four hours later, the echo of that meal activates regions of the brain associated with craving and reward seeking more powerfully than does a meal with a lower “glycemic load.”
The result: At your next opportunity to eat, you'll not only be hungrier; you'll be looking for more of the same.
The study, conducted by researchers from Harvard Medical School and Boston Children’s Hospital, was published recently in the American Journal of Clinical Nutrition.
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The Harvard researchers surmise that the striatum, a key node in the brain’s reward circuitry, may lose its sensitivity to the neurotransmitter dopamine, increasing a person’s drive to eat high-carb foods and disrupting his or her ability to control that impulse.
The team saw many of those processes at work in a lab where on two separate occasions, 12 overweight or obese young men were offered one of two meals: one high in glycemic load (including refined sugars or carbohydrates) and the other, a meal with a low-glycemic load. The meals were equal in calories, as well as in their relative protein, carbohydrate and fat content, and were rated equally tasty by subjects.
Over the next several hours, the men not only had their blood drawn to gauge their metabolic response to the meals, they also assessed their perceived degree of hunger and underwent a scan focusing on several nodes of their brain’s reward circuitry.
While the two meals elicited very similar reactions from subjects — they found both meals appealing — their brains and blood revealed dramatically contrasting responses.
The combination of plummeting blood sugar levels, a greater sensation of hunger and a memory of a meal high on the glycemic index led researchers to conclude: “This combination of physiological events may foster food cravings with a special preference for high (glycemic load) carbohydrates, thereby propagating cycles of overeating.”