Weight Loss

Eating Out of Habit

When offered a platter of cheese, pretzels, and donuts, most people will probably reach for the donuts, according to a new study. That could be because the brain values foods like donuts, with both fats and carbohydrates, more than foods high in only fats, like cheese, or only carbs, like pretzels. People could be wired to want that deadly combo: fats and carbohydrates.

According to a study at Yale, the researchers took fMRI (a functional MRI shows blood flow to parts of the brain while viewing or hearing information) images of participants’ brains while showing them photos of different foods. The brain scans showed participants’ brains lit up more when they were shown foods containing fats and carbs. This included mostly processed foods like donuts, M&Ms or hamburgers. Foods with just carbs, like bread and pretzels, and those with fats and no carbs, like cheeses, did not get the same response, regardless of the number of calories, amount of sugar, or portion sizes. This suggests that foods with both fats and carbs activate the reward centers in the brain and are more alluring and habit-forming, almost the same way drugs are addicting.

According to another study in Psychology Today, the development of habits affects our eating patterns. Researchers were interested in the activity of a certain brain region known as the ventromedial prefrontal cortex, located in the mid-lower section of the frontal lobe. A major function of this region is to anticipate the value of an expected event. This is important in the brain’s reward pathway, which manages positive and negative reinforcement of behavior. For example, when we are sitting hungrily at a restaurant and the waiter approaches the table with plates of food, neuronal fireworks light up the brain in anticipation of the meal. The ventromedial prefrontal cortex is firing away because it detects high reward. Once we are full, however, the response is vastly diminished. If the waiter were to bring another plate of food, the ventromedial prefrontal cortex would barely respond at all. The low response devalues the experience of eating, discouraging us from continuing to chow down. In short, the ventromedial prefrontal cortex participates in a feedback loop: It positively reinforces eating when we are hungry, but that very act of eating eventually causes the ventromedial prefrontal cortex to discourage us from eating and to recognize that we are full.

Those who ate out of habit were different. While the participants were hungry, their ventromedial prefrontal cortices again showed a big signal, indicating that they assigned a high reward to the food.  But when they had just eaten a large meal, the fMRI results revealed that the ventromedial prefrontal cortex activity was just as strong as it was when the subjects still had their appetites. The anticipated reward value of the snack was not downgraded, even though they were full. The feedback loop was broken. Apparently, because the subjects were eating the snacks out of habit, their brains failed to dissuade them from eating. In fact, by maintaining the reward signal, the ventromedial prefrontal cortex was doing the opposite: positively reinforcing the behavior of eating without being hungry. The development of habit changed the act of eating from something dependent on the need for nourishment and transformed it into something automated.

This may explain why we often eat when we’re not hungry. We let our habit system take over, and our eating becomes automatic. How do we permit the habit system to seize command? Can we control it? Think of it this way: there are two systems for directing our behavior, the procedural habit system and the thoughtful conscious system. Consider how we drive a car. When driving a new route, we are completely consciously aware of our decisions on the road.  After driving a common route, such as to work, we might not even remember the trip.  We can drive on autopilot, especially if our minds are busy thinking about things other than driving.

The conscious system can drive, and it can reflect on the events of the day, but it can’t do both at the same time. If the conscious system is preoccupied, the habit system is assigned the driving duties. By passively allowing thoughts to flood our minds (what we might call “spacing out”), we take our conscious system out of commission and the habit system takes over. Clearly a bad idea when behind the wheel of a dangerous weapon!

The habit system can similarly take over the process of eating. This often occurs when we are distracted by something, such as reading or watching television. Thats why we are discouraged from eating in front of the TV – it can lead to overeating by allowing the television to monopolize our conscious attention. Therefore, if we are doing something routine while watching, such as eating potato chips, the habit system will take control of that behavior. Just as a preoccupied driver may navigate on autopilot, the preoccupied diner may consume five bags of chips without thinking, while the mind is distracted by watching sports or a favorite TV show.

This study made it clear, when we allow our minds to be preoccupied, our ability to consciously control our behavior is suspended, and our behavior follows a preprogrammed course. We can choose to take control at any time, seize our brain circuitry from the habit system, and make healthier decisions.

    -Dr. Courtney

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