Simple Nudges to Boost Meal Photo Logging

Researchers wondered if a simple nudge could get people to photograph their meals more often. They knew that wearing gadgets can track steps or sleep automatically, but food logs still need a person to act. When that effort drops, the data gets spotty. When logs are incomplete, scientists can’t tell if diet helps or hurts health.

To test this, they ran a microrandomized trial inside a four‑week lifestyle study in Switzerland. Two hundred volunteers, all at least 45 years old and with a BMI of 25 or higher, took part. Each day they used a phone app to snap a picture of breakfast, lunch, and dinner. This design lets researchers try many quick variations on the same people without long waiting periods.

Before each usual mealtime, the app sent a reminder. The reminder was chosen at random with equal chance. One version warned that missing the photo would mean losing a small daily cash reward. Another version gave feedback on how many meals in a row had been logged, highlighting streaks. The third version was just a neutral prompt with no extra message.

The main question was whether the participant took a meal picture within two hours of seeing the reminder. Because the cash reward depended on completing the log, the researchers could see if the different nudges changed the odds of hitting that two‑hour window. Participants earned a set amount each day only if they logged all three meals.