Why We Underestimate Our Risk of Type 2 Diabetes


You’d think the world would be running through the streets in a movie-style panic. An epidemic of unprecedented proportions is inexorably advancing.  In our lifetimes, half of us may develop a devastating disease that could cause us to go blind, lose a leg, or die far too soon. But we aren’t in a panic. The authorities are talking it up, of course, but most of us aren’t doing much at all to prevent type 2 diabetes. We’re getting fatter by the year, and we’re moving less and less.  Many of us who already have type 2 diabetes are not making the changes that could keep its consequences at bay. Why not?

It may be because of the way that we assess risk. It’s just not a simply logical process: If it were, we’d look soberly at all the scientific evidence, judiciously realize that we and our nearest and dearest are doomed to a dread disease if we don’t get a move on, and take immediate steps to ward off the possibility. But, obviously, we’re not. Every year, the estimate of how many people will suffer from type 2 diabetes in the future goes up, not down, despite all the information that’s being stuffed into our cerebral cortices.

The reason lies in the fact that we don’t assess risk with our cerebral cortex alone. Instead, we use a conglomeration of the limited facts we’ve learned, a lot of feelings, social influences, and inborn triggers and decision-making shortcuts of which we are often not even aware. And most of those inherent triggers and shortcuts work against giving a high risk assessment to a chronic disease like type 2 diabetes.

Our brain is not one mass of brilliant human thinking matter that you could cut up like a loaf of bread and find solid human throughout. In fact, it’s the most complicated thing in the universe. To simplify things tremendously, it’s got three interconnected parts:  one part reptile at the bottom, one part mammal above that, and, at the very top, one part that we think of as purely human. And below all that are the hormones, a system of communicators secreted by glands that did the job before animals even had a nervous system. They’re still going strong in humans. Even the human part of our brain shares a lot with the monkeys: in fact, we share 99 percent of our DNA with monkeys. That explains a lot when it comes to human behavior.

Evolution does not waste its time redoing what it’s already done. The reptile brain worked just fine for reptiles, and we’ve got a reptile brain pretty much fully functional buried at the bottom of our own brains, taking care of all the things that reptiles do, including breathing, copulating, eating,  territorial aggression, and a lot of risk assessment. It’s down there a lot like the boiler room in a large building, clanking and steaming away, creating the heat that keeps the rest of the whole thing moving. It motivates us, and it drives us.  Without it, we’d never get going. We’d think, “I should make a sandwich, but it’s too much trouble,” and we’d starve to death. Or we’d think, “I should probably procreate, but what an enormous effort it would be just to get that female to let me near her.” Fortunately or unfortunately, the reptile brain is still thrashing around down there: it’s what rears into action when somebody cuts you off and you want to bash into him with your new car, as irrational as that might be.

As mammals evolved, their mammal brain grew right over the top of the reptile brain, allowing them such talents as the attachment necessary to nurse their young and various other emotional hardware.  So we’ve got an emotional brain tacked on top of our reptile brain, called the limbic system, that we share with the rest of the mammalian world.  Us and the prairie voles, we fall in love in the same way.

Finally, we’ve got our human brain, the cerebral cortex, lying over the top of these two ancient brains like a blanket. It’s the thinking part, the part that we’re aware of, the part that we think of as ourselves. It’s the cerebral cortex that says, “I think I’ll get that sandwich with extra cheese.”  It has no idea, however, of everything that went on down below in the reptile brain before that idea swam up into consciousness, all the blood sugar checking, the secretions, the signals here and the hormones there, the huffings and crankings that prompted the hunger drive. When it comes to drives and emotions, thoughts are often like a cherry on top of a volcano.  They’re a plausible explanation to yourself, so that your behavior makes sense to you when you act like a reptile or a mammal, or when you decide to eat that triple burger even though you’re 50 pounds overweight and pre-diabetic.

In fact, we still assess risk the way we did on the plains of Africa for millions of years. We’ve only been away from those plains for around 12,000 years, much too short a time to have developed an instinctive aversion to the cardiovascular drawbacks of a microwaved Hot Pocket. Evolutionarily, we are still those primitive, and constantly hungry, people. We just have cars, fast food joints, grocery stores, and a future full of dangers that we never evolved to fear.  Put those together, and you have us:  A world of chubbies who are on the high road to type 2 diabetes and global warming. 

Our response to risk, or threat, is incredibly complex, just like our brain, with its tangled elements of chemistry, neural wiring, subconscious instincts, social nature, and conscious rationalizing. The quickest way that we assess risk is instinctual, resulting in the instantaneous flight or fight response. It’s based in the amygdala, way down at the bottom of the brain, and it responds faster than thought to dangers that we have feared since the Stone Age: snakes and spiders, dark places, falling, drowning, angry faces, and social rejection. But what about new risks, risks like type 2 diabetes, with which the amygdala has no experience?

We use a combination of reason and emotion that allows us to assess risks without having to review every single fact before being able to decide.  This process of making decisions without total knowledge is called “bounded rationality,” and it uses subconscious mental shortcuts, called heuristics, to come to rapid conclusions about risk even though unbounded rationality is impossible. 

Heuristics are rules of thumb that allow us to make judgments based on limited information in a limited time. Without heuristics and emotional input, we’d be forever stumped by the smallest decision, forced to accrue ever more information in a never-ending process. When the brain is faced with the risks we encounter in our complex world, this mental shortcut toolbox springs into action to help us judge quickly whether we are in danger. But it’s fallible, unfortunately, especially when it comes to modern risks like type 2 diabetes.

One of the rules of thumb in the heuristics toolbox is “loss-aversion”; that is, we are more likely to take a risk if by doing so, we are less likely to lose something we already have. That’s another way of saying that a donut in the hand is worth the risk of diabetes 25 years down the road.

Another rule of thumb that we use is the primitive assumption that what seems good can’t be bad. Sunlight feels good, so we don’t worry as much about skin cancer as we would if sunlight felt bad. And fatty sugary foods taste so delicious that we can’t really believe, deep down, that they aren’t good for us as well.

“Optimism bias,” another tool in the very old kit, is a real power when it comes to how we assess the risk of type 2 diabetes. We all wear rose-colored glasses when estimating the risk of events in the far future, where we optimistically see diabetes as not happening to us. This bias is reduced as the future becomes the present, but by then, it’s too late to lose that belly and stop diabetes: it’s already here.

Our degree of optimism also depends on factors other than the distance of the risky event into the future. We underestimate the likelihood of unsensational causes of death like diabetes, heart disease, and stroke, three of the five leading causes of death in the US, but overestimate the risk of death from sensational or vivid causes like cancer or botulism, in part because we are subconsciously convinced that the easier it is to recall an event, the more common it must be. And it’s much easier to recall a plane going down in flames than statistics about plodding diabetes.

In addition to the mental shortcuts that we take to evaluate risks, we use a psychological shorthand to assess risks on the basis of their characteristics: Some threats just feel more frightening than others, and our feelings are powerful enough to swamp our reason in responding to those risks.

One element that ups scariness is a sense of lack of control.  The more control we feel that we have over whether or not a negative event will happen, the more optimistic we are that it won’t happen, and the less afraid we are of that risk. Because we have a great deal of control over whether we get type 2 diabetes, its risk is underestimated and we feel safe. The risk of cancer, conversely, is overestimated because it is not only random, but also memorably and vividly painful and horrifying.

Related to control is the factor of choice: If a risk is one that you’ve chosen to take yourself, you feel safer than if you are at risk because of the actions of others. If a risk is involuntary, you feel more threatened than you would if you had undertaken the risk on your own. If you choose to eat donuts by the dozen and expose yourself to the specter of diabetes, you don’t worry about diabetes as much as you would if some outside force was imposing the donuts, and the risk, on you.

Pain and suffering is a risk characteristic that makes us more afraid, and type 2 diabetes is a silent disease for a long time, one that we usually can’t even perceive without a diagnostic test. We’re just less concerned about risks that don’t involve vivid pain and suffering. If we do consider diabetes’ terrible consequences, we think of them as far into the future, where their risk is blurred and weakened by our congenital optimism bias.

Risk versus benefit plays into our assessment of a risk’s scariness, especially that of type 2 diabetes.  We intuitively weigh the value of trade-offs constantly when assessing risk, and we subconsciously downplay risks in order to enjoy benefits.  The greater the benefit, the lower we assess the corresponding risk. For example, the immediate benefit of another couple sugar donuts causes us to downplay the risk of future diabetes associated with obesity. The reptile brain drives us to eat calorie-rich food, and, as a result, we tweak the risk-benefit ratio however we must to get what we want. In order to have the benefit of that satisfying donut right now, we downgrade the associated danger of diabetes and thrust it out of our minds.

Another factor in our assessment of risk characteristics is whether the risk is natural or man-made.  Because we intuitively evaluate natural risks as less risky than artificially created ones, we assess diabetes as less scary than man-made radiation exposure, for example, though diabetes has killed infinitely more people than radiation. 

Whether a risk is catastrophic or chronic plays into our subconscious assessment of its threat.  A catastrophe is big, sudden, and awful, like a plane crash, whereas a chronic disease like diabetes develops slowly and kills people here and there, not all at once. As a result, we tend to overestimate the risk of a plane crash and underestimate that of diabetes. We also tend to overestimate the threat of a risk if it’s new and exotic and underestimate it if it’s familiar.  Diabetes is so familiar that it’s like an old shoe compared to something like the Ebola virus. So we, erroneously, assess the latter as more dangerous than the former, and it scares us more.

Dangers that affect children are assessed as far scarier and more threatening that risks that affect only adults because evolutionarily, our drive is to protect the future of the species.  Type 2 diabetes predominately affects adults, and older ones at that. Unlike the community of type 1 diabetes, which has an enormously active population of driven adults at war against it, we can’t seem to get exercised enough about type 2 to get up from the couch. If type 2 does become a threat to our children, which seems very possible at the rate we are going, maybe that will change.

Finally, we tend to assess risk the way the rest of our culture assesses risk. We have become a culture of overweight people who see ourselves as perfectly normal because we look just like all the rest of our portly neighbors who eat fast food and donuts. Fat has become the new thin. If our community doesn’t see it as a threat, then why should we? We are social animals, right down to our plump little feet. But we need to start those feet running now, because diabetes is right behind us, and it’s gaining. It’s time to start thinking with our human brain.


How Risky Is It, Really? by David Ropeik

Risk  by Dan Gardner


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