A 95 years old psychology article holds the key to solving the obesity epidemic. It's not about a long forgotten medicine or an ancient psycho-trick. It's a simple observation about the dynamics of feeding. Vindicated by neurohormonal research, here is what it means to your struggle with extra pounds. [tweet this].
When Wallace Craig dissected the feeding behavior of doves, his experimental animal of choice, he discovered the existence of two distinct phases - an appetitive and a consummatory phase [1]. He defined appetite as "a state of agitation", which continues until food is presented, whereupon phase 2 begins. That's the phase you and I call eating. It's followed by a third phase of relative rest, which Craig called the state of satisfaction. You are forgiven if you now ask "what science nugget could possibly be hidden in this platitude". But the best-hidden gems are often those, which are in plain sight. In this case it's nothing less than the model explaining why so many of us wear dress sizes, ranging from "XL" to "Oh my God, look at this!", while none of us actually wants to be seen in them.
Before I get to the beauty of Craig's observation, let me also tell you what's the acid test for any biological model: it must make sense in evolutionary biology. If it does, it still may not be the final word, but if it doesn't we can safely discard it into the heap of wishful thinking. Keeping this in mind, let's get cracking.
When Craig published his paper in 1917 he described the behaviors of his doves as instinctive. In other words, being driven by some innate processes which require no conscious decision making nor any degree of intellect. Today we know a lot more about those "innate processes", particularly that they are the result of a complex conversation between neurons and hormones playing out in the recesses of the animal brain. Not only do we know the chains of command running from brain centre to periphery we also know the hormones (at least some of them) by names, such as Neuropeptide Y (NPY) or Leptin. You don't need to remember them. What you need to remember is that "instinctive" has matured from a black box stage to the stage of neurohormonal mechanisms, which can be tested quantitatively in the lab with experimental animals.