I am guilty as charged with doing this when I am "on track". This MYTH is based on the fact that there are many thin people that eat frequent, small meals. However, most of the thin people probably aren't looking at their watch all the time-they in fact wait for their body to tell them when to eat. They eat when their body tells them to and not rely on the clock. They eat when they are hungry and stop when they are satisfied ( not stuffed!) Since that tends to be a small meal; naturally they are hungry in about 3 hours after that meal.
The whole 3 hour rule is not always convenient for me. If I know it will be near impossible for me to eat in that time frame I might either bring a small snack or eat a bigger meal! In all honesty the 3 hour rule usually works well for me. And when I am doing that on a regular basis my body does tell me when it's time to eat and it's usually in the 3 hour range. While I don't disagree with this myth, I do know what works for me. I better, it has taken me years to finally figure it out!