The Doctor Weighs In

By Dov Michaeli MD, Ph.D

It almost became a cliché: losing weight is relatively easy. That’s why you see so many “miracle diet” claiming astounding losses of weight. But why don’t we see miracle diets that tout maintenance of weight loss? Because this is the hard part of dieting. The reasons for that are both psychological and physiological, and the neurobiology of it is fascinating.

The neurobiology of diet failure

If you imagine the brain as made up of layers, the deeper ones are made of neurons that determine our response to environmental stimuli without us being conscious of it. If we come across an environmental cue that stimulates our feeding response, like a delicious looking chocolate cake, the response is an outpouring of hormones and peptides that signal to the brain: I’ve got to have that! Now, all this happens at speeds that are measured in milliseconds and microseconds—an astounding speed that eludes our consciousness. By the time our conscious thoughts take over, it is almost too late. These conscious thoughts travel in the cortex, the outer layer of the brain, at far slower speeds, measured in seconds. So by the time we try to exert some judgment (“I really shouldn’t”) the mood for the decision-making has already been formed. To counteract it is tough, and the longer we allow the “unconscious” pathways to prevail —the stronger the neuronal circuits that determine the response become. This is why it is so difficult to kick the habit, any habit, including overeating.

How can we win the battle of the brain?

The deeper, more primitive and fast moving neuronal circuits, can be restrained. By using the conscious, slow moving circuits again and again, over long periods of time, they become “unconscious”, and a lot more effective in intercepting our initial “bad” instincts. How this happens is a bit complicated and not completely known. But basically, they bypass the prefrontal cortex, the “decider” center in the brain. That is time-saving. Just imagine if every time we wanted to tie our shoe laces we had to recapitulate consciously the steps that we learned (consciously) in childhood. Repetition made it “unconscious”, and fast. Same for the multiplication table, for reading, for any learned activity that we repeat many times.

What does it have to do with weight maintenance?

A lot. If we could educate our conscious neurons to automatically resist that enticing chocolate cake, they would become “subconscious” and more effective in resisting the initial temptation. Yes, it requires repetition. And every iteration is a battle that has to be fought and won. I can understand St. Augustine ,  a 3^rd century bon vivant pagan who converted to Christianity, and who plaintively exclaimed: “Oh Lord, lead me not into temptation…but not quite yet”. The poor saint had to exile himself to the Syrian desert to deprive himself from the tempting “cues”of Rome. Even that fell short, and those “cues” came visiting and haunting. He could purge those unholy thoughts by flagellating himself—which is an extreme way of educating the subconscious. But it worked, and he could consequently devote himself to something more acceptable (to him): translating the Bible into Latin. And this brings up another aspect of “educating” the brain: the strength of the “educating” signal is as important as repetition.

But I am digressing. The “cue” that launched me into a journey of the brain was an article in the March issue of JAMA, titled “Comparison of Strategies for Sustaining Weight Loss”. This was a two-phase trial in which 1032 overweight or obese adults (38% African American, 63% women) with hypertension, dyslipidemia, or both who had lost at least 4 kg (9.2 lbs) during a 6-month weight loss program (phase 1) were randomized to a weight-loss maintenance intervention (phase 2). After the phase 1 weight-loss program, participants were randomized to one of the following groups for 30 months: monthly personal contact, unlimited access to an interactive technology–based intervention, or self-directed control.

The results: after 30 months , participants receiving personal counseling retained an average weight loss of 9.2 pounds, compared to an average of 7.3 pounds for those using the Web-based intervention and 6.4 pounds for those in the self-directed group.

After reading this blog we could have predicted this outcome. The personal counseling group received a stronger signal than the web-based group, and both received stronger “education” than the self-directed group.

You might think that a difference of 1.8 pounds between the two treatment groups may not justify the cost of personal counseling. Then think again: Each 2.2 pounds of weight loss can lower blood pressure by one point and can lower the risk of developing diabetes by 16 percent in high-risk adults . This is quite a reduction in health care costs.

 Is anybody  in Washington  listening?