If you eat mountains of food and don't exercise, you are more likely to be obese. This is not exactly news. But measuring calorie input and energy expenditure on a large scale has traditionally been difficult, and that's where Twitter comes in.
According to a paper posted on open-source submission site arXiv (and therefore not peer-reviewed), a team of researchers has created a 'Lexicocalorimeter': "an online, interactive instrument for measuring the "caloric content" of social media". The researchers parse social media for food and activity-related phrases, plug them into an equation, and produce a rough approximation of calories in and energy out for a geographic region.
The researchers compared their predictions to known public-health statistics for each state, and claim that their model "strongly correlates" with normal health and wellbeing statistics. In states where people only Tweet about bacon (hi, Dakotas), obesity is higher than in states that talk about tomatoes.