Not my comment but my guess is they might be referring to the research that shows that intermittent fasting has various health benefits. And one of the most popular ways to do intermittent fasting is 16:8 (16 hours where you fast, 8 hours where you eat), typically where you only ever eat from 12 noon until 8 in the evening, and then fast from 8 pm until noon the next day. Under those conditions, breaking the fast with a breakfast means losing out on the health benefits, and you're better off waiting until lunch.