According to Professor Susanne Klaus, a biologist at the German Institute of Human Nutrition in Potsdam, our craving for sweet foods is inborn. Sugar stimulates the brain’s reward system by triggering the release of neurotransmitters that promote a sense of well-being. And that’s not all. “Experiments have shown that the combination of sugar and fat is especially effective in stimulating the brain’s reward system,” Klaus says. That mechanism may well play a role in our fondness for chocolate and other sweets. But current research says that sugar is not actually addictive. Over the long term, though, excess sugar consumption can lead to overweight, which increases the risk for diabetes and cardiovascular disease.