We examine the relationship between BMI and food purchase behavior using a unique dataset that links individual-level food purchases to health data. We find that individuals with higher BMI are significantly more sensitive to price changes in vice categories but do not show similar sensitivity in comparable nonvice categories. We rely on past literature that defines and identifies vice categories as those that are tempting and purchased impulsively. We explore the effectiveness of a 10% price increase on vice food categories, a hypothetical policy similar in spirit to a fat tax or sugar tax. We predict that such a tax would substantially reduce consumption of these foods, and would be particularly effective in reducing consumption by individuals with higher BMI.