In a randomized clinical trial involving adults with overweight, participants who followed an ad libitum low-fat vegan diet substantially reduced the number of calories per gram of food they consumed. Researchers found that greater reductions in energy density were tied to lower calorie intake and greater weight loss, despite the absence of any instructions to eat less.

Editor's note: A previous version of this story, based on information provided by a Synchrony Financial executive, mischaracterized the collaboration between Synchrony and OpenAI. Details, quotes and characterizations attributed to Synchrony and the executive have been removed. A corrected version is below.