When sweet taste and calories do not align, the body’s metabolism is fooled, a finding that may help explain the link between artificial sweetener use and diabetes, a new Yale University study has found.

In nature, sweetness signals the presence of energy and its intensity reflects the amount of energy present. When a beverage is either too sweet or not sweet enough for the amount of calories it contains, the metabolic response and the signal that communicates nutritional value to the brain are disrupted, according to study published Aug. 10 in the journal Current Biology. A sweet–tasting, lower–calorie drink can trigger a greater metabolic response than drinks with higher calories, explaining the association between artificial sweeteners and diabetes discovered in earlier studies.

“A calorie is not a calorie,” said senior author Dana Small, professor of psychiatry at Yale University School of Medicine.

The new study shows that sweetness helps to determine how calories are metabolized and signaled to the brain. When sweetness and calories are matched, the calories are metabolized, and this is registered by brain reward circuits. However, when a “mismatch” occurs, the calories fail to trigger the body’s metabolism and the reward circuits in the brain fail to register that calories have been consumed.

“In other words, the assumption that more calories trigger greater metabolic and brain response is wrong,” Small said. “Calories are only half of the equation; sweet taste perception is the other half.”

Small noted that many processed foods contain such mismatches – such as a yogurt with low calorie sweeteners.

“Our bodies evolved to efficiently use the energy sources available in nature,” Small said. “Our modern food environment is characterized by energy sources our bodies have never seen before.”

Yale’s Maria Geraldine Veldhuizen and Richard Keith Babbs are co–first authors of the paper.