If you believe eating a food is going to make you feel bad (physically or emotionally), it probably will.
The mind is a powerful thing. Studies show that believing something is going to happen increases the likelihood that it will. If a person with depression believes the medication they are taking will help improve her mood, chances are it will. This is true even if she’s taking a placebo. In fact, in a study done by Kam-Hansen et al. more than half of the effect of some drugs is due to the placebo effect. Pretty remarkable if you ask me. I'll say it again: the mind is a powerful thing.
Athletes use this strategy to visualize the outcome they desire. If a baseball player tells himself he’s going to strike out, he probably will. But if instead he pictures himself hitting the ball he increases the odds that he will make contact when he swings the bat.
If a client tells me that she believes eating french fries will make her feel sick, she’s probably right. The fear of the french fries fuels her anxiety about the food, and the anxiety has an unpleasant effect on the gut. (Ever felt sick to your stomach because you were so anxious about something like public speaking for example?) She eats the french fries, already physiologically activated in fight-or-flight mode, and meanwhile her body is diverting her blood flow to her muscles to prepare for the fight-or-flight, which means the blood isn’t flowing to her gut where digestion occurs. Hence, the digestive process is slowed and the french fries sit in her stomach longer than food normally would. She feels nauseous. Her prophecy has come true. She just confirmed the bias she had against eating french fries.
On the flip side, if a person believes that her body can handle eating any food, and that the occasional GI upset is normal and no big deal, she’ll probably have a lot fewer issues after eating. She in turn eats in a relaxed emotional state. Blood flows normally to her digestive tract and food digests easily. She eats until she’s satisfied and stops, trusting her body will tell her when she’s hungry again.
The stories well tell ourselves about food and our bodies are powerful. What do you choose to believe?