By Paul R Burghardt, PhD

One of the most commonly asked questions is “how do I lose weight and keep it off?” We would argue that it’s in your head! At least in part.

A study by DelParigi and coworkers in the International Journal of Obesity investigated how the brains of successful dieters compared to those people who were overweight and were not dieters, responded to a 36-hour fast followed by a meal. Successful dieters were chosen from a registry of people who were able to maintain a 30 pound weight loss for more than 1 year. And when I say “meal” I mean a laboratory style meal (wink, wink); liquid form, optimally balanced to have a reproducible constituency and optimal nutrition. Soylent Green is people, it’s people!

Ok, it wasn’t THAT kind of meal, but it was still pretty scientific.

At any rate, these researchers looked at the brains of successful dieters and non-dieters after not eating for 36-hours, very soon after just a taste of the meal, and then after the study participants said they were comfortably full (satiated). This is pretty cool because not only do they look at how the brain responds to fasting, the look at the immediate response to tasting food after a fasting, and how the brain looks after satiety (feeling full). With these critical measurements one would speculate that the brains of successful dieters would respond differently after a fasting and subsequent meal , compared to people who had not dieted.

Now, I know you weren’t ready for this, but…DUNH! DUNH! DUNH! (cue dramatic look gopher)

….the successful dieter’s brain response was different from those who had not dieted!

Differences in activation occurred in an area of the brain called the Dorsal PreFrontal Cortex (DPFC). This part of the brain plays a very important role in putting the brakes on emotion and impulse, and plays a critical role in inhibiting inappropriate behaviors. This is an area of the brain the keeps you from going ballistic when some moron cuts you off on the commute home, or helps restrain you from telling your boss how it really is. This area of the brain is critical in “top-down” processing, allowing us to exert control over our emotional impulses. It is considered to be a critical site for the cognitive control of behavior, put another way this is where some of our will power comes from. In line with this, one of the duties of the DPFC is to allow us to consciously regulate what, and how much we eat.

Another cool finding was that successful dieters had lower levels of brain activity in a part of the brain called the Orbital Frontal Cortex (OFC). This area of the brain is involved in regulating the sensory experience of food with signals from our stomach to tell us when we need to eat and when we should stop. This is an area of the brain that is more reflexive or ‘unconscious’ compared to the DPFC.

So, overall successful dieters had greater activation of the DPFC and lower activation of the OFC compared to non-dieters in response to a meal. Therefore eating a meal, after a day and a half of fasting, caused a greater activation of the brain’s breaking system and lower activation of the area that processes hunger signals in successful dieters compared to non-dieters. In addition to brain activity, it is interesting to mention that metabolic measures were not different between successful dieters and people who had not dieted…suggesting that the ability to diet, lose weight and keep it off, may be mostly in our heads!

This was a very interesting study. One thing that would have taken this study into the stratosphere (in terms of coolness) would have been to add a group of ‘unsuccessful’ dieters. Those people who have tried but were not able to maintain their weight loss. By looking at people who were ‘not dieters’ the investigators may have missed an exceptionally important comparison.

Let’s think about this another way… one would have expected to see higher levels of restraint in successful dieters that had higher levels of DPFC activation (remember DPFC puts the brakes on behavior). Conversely, it would be expected that lower levels of restraint would have been seen in individuals with lower levels of DPFC activation. This is exactly what the authors reported for feelings of satiety (fullness), but what about unsuccessful dieters? Would this relationship fall apart? Would their DPFC activity not be associated with restraint? To say it a different way, are unsuccessful dieters not able to use their conscious breaking system the same was as successful dieters? Sounds like a neat idea, hopefully these researchers will follow up with that study.

Here’s the big question: Can you change the way your brain works to help you show more restraint?

Answer: Yes.

How you train your brain is the tricky part that takes some time and effort. We’d be happy to discuss this further in a future post, let us know if you’re interested.

Reference:

Journal of Obesity 2007 Mar;31(3):440-8.

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