  We present a large-scale analysis of Instagram pictures taken at 164,753
restaurants by millions of users. Motivated by the obesity epidemic in the
United States, our aim is three-fold: (i) to assess the relationship between
fast food and chain restaurants and obesity, (ii) to better understand people's
thoughts on and perceptions of their daily dining experiences, and (iii) to
reveal the nature of social reinforcement and approval in the context of
dietary health on social media. When we correlate the prominence of fast food
restaurants in US counties with obesity, we find the Foursquare data to show a
greater correlation at 0.424 than official survey data from the County Health
Rankings would show. Our analysis further reveals a relationship between small
businesses and local foods with better dietary health, with such restaurants
getting more attention in areas of lower obesity. However, even in such areas,
social approval favors the unhealthy foods high in sugar, with donut shops
producing the most liked photos. Thus, the dietary landscape our study reveals
is a complex ecosystem, with fast food playing a role alongside social
interactions and personal perceptions, which often may be at odds.
