We develop a new framework to analyze the effect of calorie posting on overconsumption of calories in a fixed-price context (e.g., fixed-price buffets). The framework demonstrates that a desire to get `a good deal’ (transaction utility) and loss aversion can induce asymmetry between two conflicting learning effects of calorie posing: a calorie-decreasing effect of learning that one was underestimating calorie contents (LUE effect) and a calorie-increasing effect of learning that one was overestimating calorie contents (LOE effect). Our laboratory snack choice experiments confirm that the LUE effect dominates the LOE effect under the context of overconsumption, which is consistent with transaction utility theory rather than loss aversion. The findings demonstrate the potential of calorie posting to mitigate overeating.