I was delighted to see that Carola Binder not only read Jason Fung's book The Obesity Code on my recommendation, but also wrote a nice blog post about it: "The Obesity Code and Economists as General Practitioners."
Carola begins by praising economists as generalists, and modern economists as scholars ready to take on any question that their training has prepared them for, whether it is part of the traditional sphere of economics or not. This a view after my own heart, as you can see from my post "Defining Economics."
Carola then has a nice treatment of calories in/calories out as an accounting identity can only become a theory by adding assumptions—and can easily be converted into a pernicious theory by adding the assumption the assumption that calories out is unaffected by calories in. Let me quote at length from this section of Carola's blog post:
The Trouble with Accounting Identities (and Counting Calories)
Fung's book takes issue with the dominant "Calories In/Calories Out" paradigm for weight loss. This idea-- that to lose weight, you need to consume fewer calories than you burn-- is based on the First Law of Thermodynamics: energy can neither be created nor destroyed in an isolated system. Fung obviously doesn't dispute the Law, but he disputes its application to weight loss, premised on "Assumption 1: Calories In and Calories Out are independent of each other."
Fung argues that in response to a reduction in Calories In, the body will reduce Calories Out, citing a number of studies in which underfed participants started burning far fewer calories per day, becoming cold and unable to concentrate as the body expended fewer resources on heating itself and on brain functioning. ...
The First Law of Thermodynamics is also an accounting identity. It is true that if Calories In exceed Calories Out, we will gain weight, and vice versa. But it is not true that reducing Calories In leaves Calories Out unchanged. And according to Fung, Calories Out may respond so strongly to Calories In, almost one-for-one, that sustained weight loss will not occur.
Proximate and Ultimate Causes
A caloric deficit (Calories In < Calories Out) is a proximate cause of weight loss, and a caloric surplus a proximate cause of weight gain. But proximate causes are not useful for policy prescriptions. Think again about the GDP=C+I+G+NX accounting identity. This tells us that we can increase GDP by increasing consumption. Great! But how can we increase consumption? We need to know the deeper determinants of the components of GDP. Telling a patient to increase her caloric deficit to lose weight is as practical as advising a government to boost consumption to achieve higher GDP, and neither effort is likely to be very sustainable. So most of Fung's book is devoted to exploring what he claims are the ultimate causes of body weight and the policy implications that follow.
In discussing insulin as an underlying cause of weight gain and weight loss, Carola makes the analogy between the development of insulin resistance and the Phillips Curve shifting:
Persistence Creates Resistance
So how does the body's set point rise enough that a person becomes obese? Fung claims that the Calories In/Calories Out model neglects the time-dependence of obesity, noting that it is much easier for a person who has been overweight for only a short while to lose weight. If someone has been overweight a long time, it is much harder, because they have developed insulin resistance. Insulin levels normally rise and fall over the course of the day, not normally causing any problem. But persistently high levels of insulin, a hormonal imbalance, result in insulin resistance, leading to yet higher levels of insulin, and yet greater insulin resistance (and weight gain). Fung uses the cycle of antibiotic resistance as an analogy for the development of insulin resistance:
Exposure causes resistance...As we use an antibiotic more and more, organisms resistance to it are naturally selected to survive and reproduce. Evenually, these resistance organisms dominate, and the antibiotic becomes useless (p. 110).
He also uses the example of drug resistance: a cocaine user needs ever greater doses. "Drugs cause drug resistance" (p. 111). Macroeconomics provides its own metaphors. In the early conception of the Phillips Curve, it was believed that the inverse relationship between unemployment and inflation could be exploited by policymakers. Just as a doctor who wants to cure a bacterial infection may prescribe antibiotics, a policymaker who wants lower unemployment must just tolerate a little higher inflation. But the trouble with following such a policy is that as that higher inflation persists, people's expectations adapt. They come to expect higher inflation in the future, and that expectation is self-fulfilling, so it takes yet higher inflation to keep unemployment at or below its "set point."
Rats and Mice: One other thing that Carola mentions along the way is Jason Fung's distrust of the applicability of animal studies for key obesity issues:
At the beginning of the book, Fung announces his refusal to even consider animal studies. This somewhat surprises me, as I thought that finding a result consistently across species could strengthen our conclusions, and mechanisms are likely to be similar, but he seems to view animal studies as totally uninformative for humans. If that is true, then why do we use animals in medical research at all?
I had forgotten that Jason Fung took that position. But in "The Case Against Sugar: Stephan Guyenet vs. Gary Taubes," I wrote:
I am inclined to agree with Stephan that rodent data do not support the idea that sugar is more harmful than fat (though it does seem to support the idea that fat plus sugar is worse than fat alone). But I am struck by the possibility that rodents might be much better adapted to highcarb diets than humans are. This may even allow them to eat sugar with less harm than humans. Am I wrong in thinking that for many, many generations rodents outside laboratories have tended to eat highcarb diets? The "many, many generations" is important. Even if rodents had only been eating highcarb diets for the same number of years as humans, the larger number of generations per century would have allowed rodents that hang around humans to be naturally selected to tolerate highcarb diets more than long-generationed humans.
Every discipline tends to develop conventions that the best research that is feasible for the typical researcher should be treated with respect. But if the best experimental research that is feasible is studies on rodents that might be much better adapted to highcarb diets than humans and small-sample-size human studies, it shouldn't make it any more persuasive to those of us who are not acculturated diet scientists for them to say "This is the state of the art."
Advocacy of Fasting as Jason Fung's Key Contribution: In her last two paragraphs, Carola says on the one hand "most of [Jason Fung's] advice is unlikely to be controversial" and then distances herself from the centerpiece of Jason Fung's advice: fasting, in the sense of going for periods time without any food. The reduction in obesity (and associated ills) to be had from eating a lowcarb diet are small compared to the reduction in obesity that is possible from scheduling in substantial chunks of time with no food.
A lowcarb diet does have some direct benefits, but the most important thing to know is that fasting is very hard when one is eating a lot of carbs when one does eat. More precisely, eating foods high on the insulin index when one does eat makes fasting very hard. (See "Forget Calorie Counting; It's the Insulin Index, Stupid" on what foods are high and what foods are low on the insulin index.) Conversely keeping one's insulin levels relatively low when one does eat makes the adjustment to an even lower insulin level while fasting much smoother.
Many pages in The Obesity Code and in Jason Fung's other book The Complete Guide to Fasting are devoted to arguing that fasting is not harmful and specifying the exceptions: such as that pregnant women and children should be wary of fasting. (Also, I would add that women who want to get pregnant should not fast. It is likely that the body takes no food as a signal it is not a good time to head toward having a baby.) There is not much scientific dispute over the claim that fasting will lead to weight loss. And there is an increasing amount of evidence that even modest increases in fasting can help. See "Stop Counting Calories; It's the Clock that Counts."
The key dispute is over whether fasting is (a) hard and (b) dangerous. It is on these grounds that Jason Fung's contentions are the most important. Given individual differences, and the current state of knowledge, individual experimentation is important in helping to figure out the answer to whether fasting is hard. My claim is that fasting for up to 20 hours might not be all that hard for you if you have already starting eating lowcarb. For those who have no particular reason to think that fasting would be dangerous for them, widespread experience with fasting for religious reasons and the many situations our ancestors faced that meant they simply didn't have food for a 20 hour stretch of time suggests that fasting that length of time is not likely to be all that dangerous.
The bottom line is that Jason Fung minus the idea of fasting would not be the Jason Fung who is my hero. What makes Jason Fung important is his trenchant advocacy of fasting as a way to fight obesity and its accompanying ills.
Technical Note on Snacking: Carola speaks of her love of grazing. I don't think of snacking per se as bad. It is length of the eating window within a day that matters. If the total length of the eating window is kept to a reasonably short time—say ten or twelve hours if one is just trying to keep a steady weight—snacking as often as desired on things with a low insulin index during the eating window is fine in my book. A warning though: much of what is called "snack food" is quite high on the insulin index and would indeed be a problem. But my snack of choice, a mix of sugar-free roasted almonds and cashews, is no problem at all.
Don't miss these other posts on fighting obesity:
- Stop Counting Calories; It's the Clock that Counts
- Forget Calorie Counting; It's the Insulin Index, Stupid
- Obesity Is Always and Everywhere an Insulin Phenomenon
- Sugar as a Slow Poison
- How Sugar Makes People Hangry
- The Case Against Sugar: Stephan Guyenet vs. Gary Taubes
- The Keto Food Pyramid
- Mass In/Mass Out: A Satire of Calories In/Calories Out
- Jason Fung: Dietary Fat is Innocent of the Charges Leveled Against It
- Faye Flam: The Taboo on Dietary Fat is Grounded More in Puritanism than Science
- Katherine Ellen Foley—Candy Bar Lows: Scientists Just Found Another Worrying Link Between Sugar and Depression
- Ken Rogoff Against Sugar and Processed Food
- Kearns, Schmidt and Glantz—Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents
- Salt Is Not the Nutritional Evil It Is Made Out to Be
- Whole Milk Is Healthy; Skim Milk Less So
- How the Calories In/Calories Out Theory Obscures the Endogeneity of Calories In and Out to Subjective Hunger and Energy
- Putting the Perspective from Jason Fung's "The Obesity Code" into Practice
- Julia Belluz and Javier Zarracina: Why You'll Be Disappointed If You Are Exercising to Lose Weight, Explained with 60+ Studies (my retitling of the article this links to)
- Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?
- Diana Kimball: Listening Creates Possibilities
- On Fighting Obesity
- Analogies Between Economic Models and the Biology of Obesity
- Debating 'Forget Calorie Counting; It's the Insulin Index, Stupid'
Also see the last section of "Five Books That Have Changed My Life."