Aside from boasting about what you just had for lunch, food photos have provided a picture for researchers to study changes in the way people eat.
A just-published study from California looked at food photos from 150 participants using a specially designed app for researchers to chew over the effects of timing food intake for humans.
Photos were collected over three weeks from people who signed up via online and print advertisements in the San Diego area.
The app was free to download, but could only be used by people who had signed an informed consent form.
Participants were required to take photos of everything they ate or drank – from a bottle of water to a bite of a cookie. Metadata was sent back of where the food was eaten and when, and the app sent a regular reminder so participants remembered to keep snapping.
But research author Shubhroz Gill, from the Salk Institute, says it quickly became second-nature for participants to take the photos.
It showed that the majority of people eat over a span of 15 hours or longer each day, with less than a quarter of the day's calories consumed before noon and more than a third eaten after 6pm.
It also revealed some common food routines, such as the consumption of coffee in the morning, alcohol at night and tea throughout the day. Yoghurt was predominantly a morning food, while sandwiches and burgers were lunchtime favourites and vegetables and ice cream eaten at night.
Chocolate and candy were recorded from 10am onward.
Senior author Associate Professor Satchidananda Panda says they were able to test whether reducing the daily duration of eating impacts heath.
They hypothesised that having a timed feeding schedule could prevent "metabolic jetlag", which is where differences in meal times during the week cause metabolic organs to get out of their circadian rhythm.
While there had been food studies done in the past, they tended to focus on what people ate, rather than when.
Assoc Prof Panda says smartphones are making a huge difference to research and could be used for personalised medicine.
"The context of the pictures spoke volumes. For example, when taken next to a keyboard, in bed, watching TV, on the sidewalk, in the car, or while filling gas," he says.
The photos revealed more than two-thirds took a nutritional supplement or vitamins, but the time they took them varied daily and the same was true for medication.
The study also looked at whether the app could help with people wanting to eat for fewer and more consistent hours.
Eight overweight people, who used to eat over a span of more than 14 hours every day, were chosen to reduce that to 10-11 hours, though no change was made to what they ate.
After 16 weeks, each lost an average of 3.5 percent excess body weight and reported feeling more energetic and had better sleep.
The authors say larger studies need to be undertaken to collect data from a number of different groups such as shift workers and those from different socio-economic levels.
Further studies hope to look at time-restricted feeding under different conditions such as sleep, activity and disease.
The results of the study were published in Cell Metabolism.