Is there a Plan B against chronic disease? — Mental models matter.

An unrealistic mental model can undermine an effective solution to a problem. A classic example is the leaky bucket mental model of a child at risk of death due to a diarrheal disease. That unrealistic mental model has killed millions of children by opposing oral rehydraton salts (ORS) as an effective treatment. Even deadlier is the refrigerator mental model of metabolism that opposes ketogenic diets as an effective treatment against chronic disease, also called noncommunicable disease or NCD. According to the World Health Organization, “Noncommunicable diseases (NCDs) kill 40 million people each year, equivalent to 70% of all deaths globally.” […] ”Cardiovascular diseases account for most NCD deaths, or 17.7 million people annually, followed by cancers (8.8 million), respiratory diseases (3.9 million), and diabetes (1.6 million). These 4 groups of diseases account for 81% of all NCD deaths.”

This essay describes both of those unrealistic mental models.

“Leaky bucket” mental model

An effective treatment that significantly reduces the risk of death due to diarrheal disease is oral rehydration salts (ORS), described in the oral rehydration therapy (ORT) case study by Molly Kinder.

Diarrhea is an intestinal disorder characterized by abnormally frequent and watery stools. Acute watery diarrhea lasts just a few hours or days and can quickly become deadly. Bacteria (such as E. coli and salmonella), protozoa, and viruses can all cause diarrhea; of these, rotavirus is the leading cause in developing countries. […]

Dehydration is diarrhea’s most acute effect. During an episode of diarrhea, the body expels electrolytes (sodium, chloride, potassium, and bicarbonate) and water — all of which are necessary for life. Life-threatening dehydration ensues when the loss of the essential fluids is not replaced quickly and the body begins to ‘dry up.’ Symptoms of dehydration include thirst, restlessness, sunken eyes, rapid breathing, heart failure, bloated stomach, convulsions, and fainting. When fluid loss reaches 10 percent, dehydration turns fatal. […]

Avoiding death from dehydration requires the swift restoration of lost fluids and electrolytes. Until the development of oral rehydration therapy (ORT) in the 1960s, the only effective treatment available was through intravenous infusions in a hospital or clinic that ‘rehydrated’ patients. Intravenous therapy is far from a treatment of choice in the developing world because of its high cost, the hardship patients experience in traveling to clinics from remote areas, and the shortages of both trained personnel and supplies. Many people instead turn to popular drugs, including antibiotics, which can stop diarrhea but still expose the child to the risk of dehydration. The majority of these drugs demonstrate no proven health benefit and in some cases cause dangerous side effects.

A massive cholera outbreak in refugee camps on the border of India and Bangladesh in the 1970s exposed the limitations of intravenous treatment and paved the way for a radically different approach to treating dehydration. In 1971, the war for independence in what is now Bangladesh prompted 10 million refugees to flee to the border of West Bengal, India. The unsanitary conditions in the overcrowded refugee camps fueled a deadly cholera outbreak characterized by fatality rates approaching 30 percent. Health officials from the Indian and West Bengal governments and relief agencies faced a daunting task: Conditions were squalid and chaotic, intravenous fluid was in scarce supply, treatment facilities and transportation were inadequate, and trained personnel were limited. Mass treatment with intravenous therapy alone would not halt the impending crisis.

Dr. Dilip Mahalanabis, a cholera expert at the Johns Hopkins Centre for Medical Research and Training in Calcutta and head of a health center at one of the refugee camps, proposed an alternative to the intravenous treatment. He suggested the camp use a new method of oral replacement of fluid, known as oral rehydration therapy, that had been developed in the 1960s in Bangladesh and Calcutta.

The science was as ingenious as it was simple: A solution of water, salt, and sugar was found to be as effective in halting dehydration as intravenous therapy. Dr. Mahalanabis’ team recognized the many advantages of oral therapy over the intravenous rehydration: It is immensely cheaper, at just a few cents per dose; safer and easier to administer; and more practical for mass treatment. ORT, however, had still not been tested in an uncontrolled setting, and skeptical health specialists cautioned that only health professionals and doctors should administer the new therapy.

Mahalanabis’ team moved quickly to introduce the treatment to the 350,000 residents of the camp. Packets of table salt, baking soda, and glucose were prepared in Calcutta at the diminutive cost of one penny per liter of fluid. The solution was widely distributed, with instructions about how to dissolve it in water. Despite the shortage of trained health personnel, large numbers of patients were treated, with mothers, friends, and patients themselves administering the solution.

The results were extraordinary: At the height of the outbreak, cholera fatalities in the camp using ORT dropped to less than 4 percent, compared with 20 percent to 30 percent in camps treated with intravenous therapy.

The success of ORT in the refugee camps demonstrated that diarrhea could be treated effectively and inexpensively even in the world’s most impoverished and isolated regions. Thus, ORT, heralded by Lancet as ‘potentially the most important medical discovery of the 20th century,’ gave the world a powerful tool to reduce the estimated 5 million annual deaths from diarrhea recorded in the 1970s. In 1972, one year after Mahalanabis’ results from the refugee camps, the WHO made ORT the world’s standard treatment for diarrhea, setting in motion a revolution that would drastically cut diarrheal deaths in the following decades.

Egypt was one of the pioneers of national-level administration of ORT, and its experience represents a tremendous public health success story. In the 1970s, as the efficacy of ORT was being proved, diarrhea posed a serious public health problem in the North African country. In 1977, diarrhea caused at least half of the large number of infant deaths in Egypt (the infant mortality rate at the time was 100 per 1,000 live births). That year, the Egyptian Ministry of Health introduced packets of Oralyte, oral rehydration salts (ORS) packaged for the United Nations Children’s Fund (UNICEF), in its public clinics; soon after, a parastatal company began manufacturing ORS packets called Rehydran for sale at pharmacies.

Despite the availability of oral rehydration salts (ORS), progress by the early 1980s was disappointing. Few mothers were aware of the new treatment and even fewer used it. In 1982, only 10 percent to 20 percent of diarrhea cases used ORS, and most of the ORS lay untouched in warehouses and clinics. Instead, the most widespread treatments were ineffective anti-diarrheal medicines, and physicians commonly recommended that mothers withhold fluids and food and suspend breast-feeding — dangerous advice that was at odds with the effective use of ORT. […]

Beginning in 1980, the Bangladesh Rural Advancement Committee, a large nongovernmental organization, began a program to promote ORT in rural Bangladesh. The program, the largest nationwide ORT program ever undertaken, trained tens of thousands of oral rehydration workers, or female health workers aged between 20 and 50, who went door-to-door training mothers about dehydration and ORT. The health workers visited each household in the program area and taught at least one woman in the household the “10 points to remember,” including what diarrhea and dehydration is and looks like, how to rehydrate through ORT, how to make the solution at home and when to use it, when to call the doctor, and when to continue feeding. The oral rehydration workers demonstrated how to make a homemade oral solution called lobon-gur through the “pinch and scoop method” by mixing a 3-finger pinch of salt, a fistful of sugar, and a liter of water. (Today, packaged oral rehydration salts are widely available in most of the country, including the rural areas.)

The program employed an innovative performance-based salary system that provided incentives for oral rehydration workers to accurately and thoroughly teach mothers the 10 points. Approximately one month following the workers’ visits, a monitor would randomly select and visit 10 percent of the households. The monitor would ask the mother questions about the 10 points and test her ability to make the mixture properly. The health worker would be paid based on how much the mothers within the program area had learned. […]

Between 1980 and 1990, 13 million mothers were taught to make oral rehydration mixtures in their homes. An evaluation of more than 7,000 households found that between 25 percent and 52 percent of cases of “severe diarrhea” used the lobon-gur mixture. Today, the usage rate of ORT in Bangladesh is 80 percent, one of the highest in the world. ORT is now part of the Bangladeshi culture: Studies show mothers are transmitting ORT knowledge to the next generation. […]

Despite this success, some elements of the program were disappointing. The private sector has been slower at converting to ORT than have the public facilities; because private physicians see nearly three quarters of all cases, this gap will need to be addressed. And the market for anti-diarrheals remains large — a continued trend that poses a threat to ORT use and to children’s lives.”

The MacArthur award winning behavioral economist Sendhil Mullainathan describes in his TED Talk this rather odd behavior of opposing an effective treatment. In general, he describes why we continue to have unrealistic mental models. In particular, he describes the “leaky bucket” unrealistic mental model that opposes the use of oral rehydration salts (ORS) to treat diarrheal disease:

What’s going on here? Well the easy answer is, we just haven’t gotten those salts to those people. That’s actually not true. If you look in areas where these salts are completely available, the price is low or zero, these deaths still continue unabated. Maybe there’s a biological answer. Maybe these are the deaths that simple rehydration alone doesn’t solve. That’s not true either. Many of these deaths were completely preventable, and this is what I want to think of as the disconcerting thing, what I want to call “the last mile” problem.

See, we spent a lot of energy, in many domains — technological, scientific, hard work, creativity, human ingenuity — to crack important social problems with technology solutions. That’s been the discoveries of the last 2,000 years, that’s mankind moving forward. But in this case we cracked it, but a big part of the problem still remains. Nine hundred and ninety-nine miles went well, the last mile’s proving incredibly stubborn.

Now, that’s for oral rehydration therapy. Maybe this is something unique about diarrhea. Well, it turns out — and this is where things get really disconcerting — it’s not unique to diarrhea. It’s not even unique to poor people in India. […]

Alright, what’s the problem? The problem is this little three-pound machine that’s behind your eyes and between your ears. This machine is really strange, and one of the consequences is that people are weird. They do lots of inconsistent things. They do lots of inconsistent things. And the inconsistencies create, fundamentally, this last mile problem. See, when we were dealing with our biology, bacteria, the genes, the things inside here, the blood? That’s complex, but it’s manageable. When we’re dealing with people like this? The mind is more complex. That’s not as manageable, and that’s what we’re struggling with.

Let me go back to diarrhea for a second. Here’s a question that was asked in the National Sample Survey, which is a survey asked of many Indian women: “Your child has diarrhea. Should you increase, maintain or decrease the number of fluids?” Just so you don’t embarrass yourselves, I’ll give you the right answer: It’s increase. Now, diarrhea’s interesting because it’s been around for thousands of years, ever since humankind really lived side by side enough to have really polluted water. One Roman strategy that was very interesting was that — and it really gave them a comparative advantage — they made sure their soldiers didn’t drink even remotely muddied waters. Because if some of your troops get diarrhea they’re not that effective on the battlefield. So, if you think of Roman comparative advantage part of it was the breast shields, the breastplates, but part of it was drinking the right water.

So, here are these women. They’ve seen their parents have struggled with diarrhea, they’ve struggled with diarrhea, they’ve seen lots of deaths. How do they answer this question? In India, 35 to 50 percent say “Reduce.” Think about what that means for a second. Thirty-five to 50 percent of women forget oral rehydration therapy, they are increasing [risk] — they are actually making their child more likely to die through their actions. How is that possible? Well, one possibility — I think that’s how most people respond to this — is to say, “That’s just stupid.” I don’t think that’s stupid. I think there is something very profoundly right in what these women are doing. And that is, you don’t put water into a leaky bucket.

So, think of the mental model that goes behind reducing the intake. [It] just doesn’t make sense. Now, the model is intuitively right. It just doesn’t happen to be right about the world. But it makes a whole lot of sense at some deep level. And that, to me, is the fundamental challenge of the last mile.

This first challenge is what I refer to as the persuasion challenge. Convincing people to do something — take oral rehydration therapy, intercrop, whatever it might be — is not an act of information: “Let’s give them the data, and when they have data they’ll do the right thing.” It’s more complex than that. […] Diarrhea, and many last mile problems, are like that. They are situations where the mental model doesn’t match the reality.

See what’s really puzzling and frustrating about the last mile, to me, is that the first 999 miles are all about science. No one would say, “Hey, I think this medicine works, go ahead and use it.” We have testing, we go to the lab, we try it again, we have refinement. But you know what we do on the last mile? “Oh, this is a good idea. People will like this. Let’s put it out there.” The amount of resources we put in are disparate. We put billions of dollars into fuel-efficient technologies. How much are we putting into energy behavior change in a credible, systematic, testing way?

Now, I think that we’re on the verge of something big. We’re on the verge of a whole new social science. It’s a social science that recognizes — much like science recognizes the complexity of the body, biology recognizes the complexity of the body — we’ll recognize the complexity of the human mind. The careful testing, retesting, design, are going to open up vistas of understanding, complexities, difficult things. And those vistas will both create new science, and fundamental change in the world as we see it, in the next hundred years.”

“Refrigerator” mental model

Every bit as unrealistic as the “leaky bucket” mental model of a child with a diarrheal disease, most people think of the metabolism of a person as a “refrigerator.” That unrealistic mental model is consistent with the following three heavily used phrases that initially seem intuitively correct. However, their flaws appear when considered in the context of reality instead of the “refrigerator” mental model.

1) You are what you eat.

Somewhat like a refrigerator, your body can store some of what you eat. A typical refrigerator has room for a lot of different foods. The meat compartment can hold a variety of meats, and the shelves can hold a lot of sugary drinks in bottles and cans, but the refrigerator’s butter compartment can hold just a couple pounds of butter. In reality, unlike in a refrigerator, your metabolism is highly constrained by your body’s capacity to store nutrients. Your body’s storage capacity for dietary protein is minuscule (i.e., just the amount to rebuild currently damaged muscles), and your body’s storage capacity for glucose is limited to about one pound (i.e., typically about 80% in all of your muscle cells, more if you are unusually muscular, typically less than a half an ounce in all of your blood, and the rest in your liver cells), but your body has a virtually unlimited storage capacity for fat, which is the destination for all excess dietary sugar and protein.

Therefore, what most people think of as a refrigerator-like metabolism is actually more like a butter maker. This is easy to verify on your own metabolism. A blood glucose meter costs about $9 and blood glucose test strips cost about 18 cents per strip. Eat a large serving of meat and use your glucose meter to see how the meal raises your blood glucose, which typically gets converted to fat because the standard American diet typically keeps our glucose storage full.

2) A calorie is a calorie.

A refrigerator is indifferent to the types of food you put in it. In reality, unlike in a refrigerator, the types of food you eat directly drive your metabolism. We know that eating certain carbohydrates (e.g., sugar, highly refined grains) can significantly increase your blood glucose, and chronically high levels of blood glucose can cause

  • hardening of the arteries,
  • heart disease,
  • stroke,
  • kidney disease,
  • blindness,
  • increased infections, and
  • loss of toes, feet, or fingers caused by poor circulation and infections.

Reducing the risk of that damage, a metabolism responds to a high blood glucose by releasing insulin, which typically lowers blood glucose. However, we also know that a large serving of fat quickly reduces your body’s sensitivity to insulin, thereby interfering with your body’s ability to lower high levels of blood glucose. For example, the recent article Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance in The Journal of Clinical Investigation by Hernandez et al. documents a study in which fourteen lean and healthy individuals drank 1.18 grams of palm oil for each Kilogram of body weight (i.e., that is 6.2 tablespoons of palm oil for a 150 pound person), resulting in “decreased whole-body, hepatic, and adipose tissue insulin sensitivity by 25%, 15%, and 34%, respectively.

Although it may initially seem obvious that eating even more fat would increase your risk of damage due to high blood glucose even more (i.e., by your becoming even less sensitive to insulin), in reality your metabolism is highly nonlinear and increasing your dietary fat does not necessarily increase your risk of damage due to high blood glucose. Specifically, if your diet replaces enough glucose with enough fat, your metabolism switches into a state of ketosis in which your cellular preference for fuel switches from glucose to fat … because there is not enough glucose. In ketosis, blood glucose remains relatively low and therefore the problem of reduced insulin sensitivity is much less of an issue because insulin is no longer needed to lower an already low level of blood glucose.

In other words, your metabolism is more like an intricate dance that quickly responds to your food choices than it is like a refrigerator that operates the same regardless of the types of food you put in it. This is easy to verify on your own metabolism. A blood glucose meter costs about $9, blood glucose test strips cost about18 cents per strip, a blood ketone meter costs about $12, and blood ketone test strips cost about $1.63 per strip. Eat an avocado (i.e., about 75% of its calories are from fat) for breakfast and see how it affects your blood glucose and blood ketones. For the next day’s breakfast, eat approximately the same amount of calories in toast instead of avocado. See the difference in how it affects your blood glucose and blood ketones. (Measuring ketones is a cheap surrogate to measuring insulin. As insulin increases, ketones decrease.)

3) Eat less and exercise more.

It is a truism that a refrigerator will gain weight if you put in more food than you take out. Similarly, a refrigerator will lose weight if you put in less food than you take out. As is often the case, the interesting question is, ‘Why?’ In reality, unlike in a refrigerator, your metabolism includes a lot of chemical signaling that affects your appetite. Although we are still a long way from fully understanding all of that signaling, it is interesting that a Roux en-Y gastric bypass surgery skips over the first meter of small intestine and the morbidly obese gastric bypass patients immediately lose their long unwanted obsession with food. (Some researchers believe that a significant increase in the Glucagon-like peptide (GLP)-1 levels of the gastric bypass patients may be a hint as to what is going on.) Similarly, it is interesting that hunger is much tamer for ketogenic dieters. Most ketogenic dieters conclude that two meals per day are enough.

[end of installment 2]