Fooling the Brain; Not a Good Idea:
Jacob Schor ND, FABNO
July 25, 2012
The non-caloric sweeteners used in diet soda confuse the brain and may lead to overeating and weight gain.
Switching to diet soda has never helped people lose weight the way they hoped. Two new studies have shed light on what is going wrong.
Think of Aesop’s fable, ‘The Boy Who Called Wolf’
In February 2008, a study by Denver based scientists on brain reaction to real and artificial sugars was published in the journal Neuroimage. Employing functional magnetic resonance imaging, these researchers watched the brain activity of 12 women as they tasted water sweetened with either sugar or an artificial sweetener. Both solutions activated a response in their brains but in different areas. Regular sugar triggered a stronger response than the artificial sweetener. Only real sugar engaged the dopaminergic areas in the midbrain that signals pleasantness. It seems that the brain distinguishes between caloric and non-caloric [real and fake] sweeteners even though the participants were unable to tell the difference. 
In the May 2012 issue of Physiology and Behavior, researchers from San Diego, took this a step further. Twenty-four volunteers were selected; half drank diet soda regularly, at least once a day. The other twelve rarely, if ever, drank diet soda. Again using functional magnetic resonance brain scans, the researchers analyzed how the brains responded to small amounts of water sweetened with either sugar or saccharin. Again, while participants couldn’t distinguish between the sweeteners, their brains did. Well at least the brains of those unaccustomed to artificial sweeteners. In the group that didn’t drink diet soda, sugar and saccharin lit up distinctly different parts of the brain. In those who drank diet soda regularly, no clear difference was detected. The brains no longer could tell the difference. Among the diet soda drinkers, the more often they drank diet soda, the less the brain region called the caudate head was activated. This area, the caudate head, is associated with food motivation and reward sensations. Decreased activation of this area is linked to a higher risk for obesity.
If we fool the brain too many times with ‘fake’ sweeteners, it forgets how to sense energy intake or feel satiety from eating sweets. The more diet soda consumed, the worse this gets.
This may finally explain why switching to diet foods seems to backfire. Initially the brain knows it’s being cheated and increases caloric intake. At some point it loses the ability to track calories and no longer believes that anything is sweet, never feeling satisfied. This may explain why obesity rates have only increased over the years seemingly in direct proportion to the oceans of diet soda drunken.
If you want to lose weight, it works best to eat real food, but less of it, and exercise more.
1. Frank GK, Oberndorfer TA, Simmons AN, Paulus MP, Fudge JL, Yang TT, Kaye WH. Sucrose activates human taste pathways differently from artificial sweetener. Neuroimage. 2008 Feb 15;39(4):1559-69. Epub 2007 Nov 19.
2. Green E, Murphy C. Altered processing of sweet taste in the brain of diet soda drinkers. Physiol Behav. 2012 May 11. [