Think about the significance of breakfast: it’s the first meal after (hopefully) about eight hours of fasting. According to conventional wisdom, any sort of fasting is bad: it starves your muscles, drags down your metabolism, impairs your thought processes, and basically sabotages any of your efforts to be a better human.
But that’s not true. Short-term fasting showed no impact on cognitive abilities when research subjects didn’t know they were skipping breakfast. Additionally, skipping the first meal has no impact on metabolism, and in fact, it’s actually known that fasting under 48 hours actually increases your metabolism.
Surely those claims on your cereal box must have been based on something? Well, they were, but incorrectly so. Research supporting breakfast usually resulted in correlational studies -- so instead of proving breakfast caused those benefits, it just showed that people who ate breakfast also happened to experience those effects too.
For example, a study may survey people for their eating habits and find that breakfast eaters tend to be more overweight than their skipping counterparts. It’s likely, however, that breakfast eaters were more health conscious, and thus took better care of their weight. In actual fact, controlled experiments that split groups into an experimental group and a "control" group -- rather than rely on surveys -- have found that, at best, skipping doesn't really make a difference.