How your brain makes you overeat

Turns out the more we desire a food, the more we have to consume to feel satiated.

  • The brain's reward system releases dopamine when tasting food.
  • Researchers at Max Planck discovered a second dopamine release in the stomach, affecting higher cognitive functions.
  • The more we desire a food, the weaker the second release, which might lead to overeating.

As if losing weight wasn't hard enough. A new study from researchers at the Max Planck Institute for Metabolism Research reveals that we're rewarded twice when eating. The first dopamine kick occurs when tasting food; the second, when the food reaches your stomach.

Making this process even more insidious, the more you crave the food, the less dopamine is produced by your stomach, which the researchers believe might lead to overeating.

Previous research has shown that even thinking about food starts the process of salivation by releasing a protein enzyme, amylase, which helps break down food before it reaches your stomach. Interestingly, if you head to your favorite restaurant and they're out of the dish you've been craving, the emotional discontent is real. Your brain has been tricked—well, your brain tricked itself.

For this study, the researchers write that pleasant taste and nutritional value are both reinforcers for consuming certain foods. Yet the desire for a gustatory-pleasing experience overrides health concerns. They point to research highlighting the brain's dopaminergic system as the key mediator in overeating. In simple terms: If we like it, we eat it, and keep eating it beyond the point of satiation.

As the team puts it:

Highly processed food with added fat and sugar is known to include higher food wanting and overconsumption.

This has been expressed in evolutionary terms elsewhere. Sweet and fats were rare throughout most of history. When our ancestors discovered them, they gorged. Now, at a time when the entirety of taste profiles and nutrients are a few swipes on your phone away, the dopaminergic system hasn't caught up to the news that we don't need all those tastes all the time. Dopamine keeps us swiping.

To test the physiological reasons for this, the team at Max Planck recruited 12 normal-weight male volunteers (average age, 56) to drink either a milkshake or a tasteless chemistry experiment in a glass. They then performed PET (positive emission topography) scans on their brains. Lead researcher, Marc Tittgemeyer, explains the results:

With the help of a new position emission topography technique we developed, we were not only able to find the two peaks of dopamine release, but we could also identify the specific brain regions that were associated with these releases.

The first release, as expected, occurred in the reward system. They identified dopamine release in the lateral hypothalamus and dorsal striatum, as well as the orosensory pathways, mesolimbic dopamine system, and regions associated with reward value signaling, memory, and inhibition control. This complex interplay of regions connects desire with continual consumption, especially those last two regions, the hippocampus and lateral ventral anterior nucleus of the thalamus.

The second dopamine release occurred 15-20 minutes later, when the milkshake was in their stomachs. These higher cognitive function regions include the anterior insula, ventral posterior medial nucleus of the thalamus (again), caudate nucleus, palladium, and amygdala, among others. Basically, the brain was being told that a) everything is all good and b) I like it.

The strangest result was the fact that the more a volunteer craved the milkshake, the less dopamine was produced in the second stage. As study co-author, Heiko Backes, states:

On one hand, dopamine release mirrors our subjective desire to consume a food item. On the other hand, our desire seems to suppress gut-induced dopamine release.

The researchers agree that this might be the physiological reason we overeat. As with many drugs, we desire the feeling we originally received when first consuming the food. The stronger the desire, the less effective it is. Our response is to keep returning in hopes of chasing down that initial feeling.

Of course, 12 men drinking milkshakes is just the beginning of this research, but fascinating at that. The more we understand why we overeat, the closer we are to finding solutions.

--

Stay in touch with Derek on Twitter and Facebook.

​There are two kinds of failure – but only one is honorable

Malcolm Gladwell teaches "Get over yourself and get to work" for Big Think Edge.

Big Think Edge
  • Learn to recognize failure and know the big difference between panicking and choking.
  • At Big Think Edge, Malcolm Gladwell teaches how to check your inner critic and get clear on what failure is.
  • Subscribe to Big Think Edge before we launch on March 30 to get 20% off monthly and annual memberships.
Keep reading Show less

For a long time, the West shaped the world. That time is over.

The 21st century is experiencing an Asianization of politics, business, and culture.

Videos
  • Our theories about the world, even about history or the geopolitics of the present, tend to be shaped by Anglo perspectives of the Western industrial democracies, particularly those in the United States and the United Kingdom.
  • The West, however, is not united. Canada, for instance, acts in many ways that are not in line with American or British policies, particularly in regard to populism. Even if it were united, though, it would not represent most of the world's population.
  • European ideas, such as parliamentary democracy and civil service, spread across the world in the 19th century. In the 20th century, American values such as entrepreneurialism went global. In the 21st century, however, what we're seeing now is an Asianization — an Asian confidence that they can determine their own political systems, their own models, and adapt to their own circumstances.
Keep reading Show less

Why modern men are losing their testosterone

Research has shown that men today have less testosterone than they used to. What's happening?

Flickr user Tom Simpson
Sex & Relationships
  • Several studies have confirmed that testosterone counts in men are lower than what they used to be just a few decades ago.
  • While most men still have perfectly healthy testosterone levels, its reduction puts men at risk for many negative health outcomes.
  • The cause of this drop in testosterone isn't entirely clear, but evidence suggests that it is a multifaceted result of modern, industrialized life.
Keep reading Show less

Why the ocean you know and love won’t exist in 50 years

Can sensitive coral reefs survive another human generation?

Videos
  • Coral reefs may not be able to survive another human decade because of the environmental stress we have placed on them, says author David Wallace-Wells. He posits that without meaningful changes to policies, the trend of them dying out, even in light of recent advances, will continue.
  • The World Wildlife Fund says that 60 percent of all vertebrate mammals have died since just 1970. On top of this, recent studies suggest that insect populations may have fallen by as much as 75 percent over the last few decades.
  • If it were not for our oceans, the planet would probably be already several degrees warmer than it is today due to the emissions we've expelled into the atmosphere.
Keep reading Show less