Calorie labeling has been suggested as an antiobesity measure; however, evidence on its effects is scarce and formatting guidance not well defined. The aim of this study was to test the effects of prominent calorie labeling on sales of the labeled items.Prominent calorie labels were posted in front of two popular items for a period of 1 mo. Sales were recorded for 2 mo consecutively, before and during labeling.Muffins sales (the higher-calorie item) fell by 30%, whereas sales of scones rose by 4%, a significant difference (χ2 = 10.258; P = 0.0014).Calorie labeling is effective when noticed. Wider adoption of calorie labeling for all food businesses and strengthening legislation with formatting guidelines should be the next step in public health policy.