The Link between Behavior and Eating

Remember when you had a difficult day as a child.  Your mother or father may have tried to cheer you up with your favorite desert (ice cream or a cookie!) and a pat on the back or a hug.  As children, we all remember the times when we ran late for school and skipped breakfast to avoid missing the bus.  Or when we ate desert or snacks and didn’t want to eat our dinner.  I remember the times as a child when my parents, after discovering an empty refrigerator and not want to go shopping for food, ordered pizza and bread sticks out of convenience and had it delivered.

 As humans mature, behaviors become more fixed and predictable.  These behaviors include the selection of food and how it is eaten.  Food preferences intersect with life skills, such as cooking, time and stress management.  If there is a challenge to the consistency of our daily routine from a real or perceived stress or trauma, eating patterns may change.   Many people can recall how adjustments, such as a change in jobs, relationship status or the death of a loved one or having a child, brought a conflict to the routine.  Any of these changes in homeostasis can increase the risk of becoming overweight.  There is a direct correlation with prolonged distress, abuse or trauma and sleep deprivation and obesity.  There are many factors that are likely behind this and will be explored further.

The science behind behavior and why it is difficult to lose weight

As an experiment, I went on a super-low carbohydrate diet.  Although I usually keep a fairly low-carbohydrate diet, I admit to indulging more lately with fruit and chocolate or my children’s leftover salty snacks.  It was with this increasing momentum toward the “dark side”, that I decided I would try this change to see how it affected my behaviors with these types of foods.

The first few days was especially challenging, with a feeling of nausea, some gnawing stomach cramps, inattention and fixation on food, while experiencing cravings for some of my go-to-sweets, including fruit and chocolate.  I woke up the morning of my second day of no carbohydrates after I had a dream of eating fried dough loaded with powder sugar, a food that I haven’t had since I was a child. 

The images produced in my brain got me to thinking about what how our brains are affected by our life experiences as it relates to stress and food.

As images of a memory of <insert sweet substance> are evoked in our minds with craving, deep forces rooted in our brain are at play.  Although there is a “blood-brain barrier” from the body, modulators known as neurotransmitters can be actuated in the body and have effects on the brain.    Indeed any action, food, drink or substance that results in a positive response leaves an impression in the rewards centers of the brain, the nucleus accumbans.  The memory center – the hippocampus and the emotional center – the amygdala are also involved in a concerted effort in reinforcing a behavior.   A surge of the neurotransmitter dopamine, produces a feeling of desire that activates the memory centers, leading to repeating the behavior in the future.    Another neurotransmitter serotonin does not cross the blood brain barrier and is produced in the brain (5% of production) and body (95% of production in GI cells).  Through its action in the brain, there is an increase of pleasure and satisfaction.  Picture a boy who is given a cookie by his mother when he falls down and hurts himself.  A behavior loop is forged through these neurotransmitters, by which these earlier experiences serve as a future “fast track” to pleasure and calming in the setting of a future adversity.  This may be why we are more likely to treat ourselves to higher sugar, salt and fatty foods, when we are experiencing stress.

The stronger the surge of dopamine is, the greater is the “high” and the future desire and craving.  Unfortunately, the brain does adjust after repeated stimulation by down-regulating the amount of inhibitory dopamine receptors (D2) available, which leads to a dampening of future pleasure.  Similarly, serotonin levels have been shown to decrease in the brain, in the setting of addiction.  This creates a behavior that seeks to find the pleasure of the initial use with diminishing returns, causing one to increase dosage for the similar response.  In the absence of the signal, there is an enhanced period of displeasure.  Interestingly, with regard to serotonin deficiency, there is a greater tendency to overeating, obsessional thinking and depression and anxiety, satisfied in part by repetition of the behavior.    Behavioral cycles generated by fluctuations in dopamine and serotonin are greatest with cigarette, alcohol, drug use and a high sugar diet and can be especially difficult to break.

As with drugs of abuse, a high sucrose diet has been shown in rat models to increase activity of dopamine, particularly after high sucrose intake.    Acetylcholine is another important neurotransmitter that works in concert with dopamine in the nucleus accumbens and promotes muscle action and learning and memory. In this study, dopamine levels peaked early into the meals, while acetylcholine peaked toward the end of the meal.  The release was delayed after rats were fed a high sucrose diet, suggesting that this may affect the signaling of satiety, allowing rats to increase intake. When rats are fed regular high sucrose diets, there develops dopamine desensitization in these rats, suggesting sucrose dependence tantamount to what would be seen in drug dependence.  The rats in this study also showed behaviors mimicking drug dependence, with an increased consumption of sucrose, including binge eating in the first hour of access and escalation of daily sugar intake.  They even showed signs of withdrawal upon sucrose deprivation.  

Simply put, the brain and body communicate and form a pathway to our thoughts and actions.  A behavior may represent a higher form of instinct – conditioning, and attached to this is a reward that reinforces continued use.  Therefore, one can imagine how truly difficult it is to change this behavior.  Removal of what is interpreted as a reward is met with resistance both biologically (including the actions we are driven to do or the thoughts we have), enough often to sabotage our efforts.  When you see a person with advanced lung disease smoke into their tracheostomy tube or an intravenous drug abuser inject just after they had a valve surgery for infective endocarditis – and otherwise defy reason – you can gain an appreciation that there are powerful circuits that are being activated with these addictions

Our eating patterns and selection of foods are reinforced behaviors, which are sometimes linked to coping with an adversity, whether real, such as verbal or physical abuse and other trauma, or perceived, such as fears and anxieties of the past and future welling up in the present.  Sometimes a pattern of behavior repeats itself not from the original type of stimulus but from a perceived stressor.  Thus, a maladaptive behavior becomes reinforced.  Put a reward likes cigarettes, drug and alcohol – and even sugar – into the pattern, and it creates a biological adaptation to these substances – resulting in tolerance and addiction – with a behavior leading to increased consumption.  This could manifest as someone binging or “grazing” large quantities of sugar in food.