The Obesity Code. Jason Fung
Since nobody wants to be fat, doctors in particular should have both the knowledge and the dedication to stay thin and healthy.
So why are there fat doctors?
The standard prescription for weight loss is “Eat Less, Move More.” It sounds perfectly reasonable. But why doesn’t it work? Perhaps people wanting to lose weight are not following this advice. The mind is willing, but the flesh is weak. Yet consider the self-discipline and dedication needed to complete an undergraduate degree, medical school, internship, residency and fellowship. It is hardly conceivable that overweight doctors simply lack the willpower to follow their own advice.
This leaves the possibility that the conventional advice is simply wrong. And if it is, then our entire understanding of obesity is fundamentally flawed. Given the current epidemic of obesity, I suspect that such is the most likely scenario. So we need to start at the very beginning, with a thorough understanding of the disease that is human obesity.
We must start with the single most important question regarding obesity or any disease: “What causes it?” We spend no time considering this crucial question because we think we already know the answer. It seems so obvious: it’s a matter of Calories In versus Calories Out.
A calorie is a unit of food energy used by the body for various functions such as breathing, building new muscle and bone, pumping blood and other metabolic tasks. Some food energy is stored as fat. Calories In is the food energy that we eat. Calories Out is the energy expended for all of these various metabolic functions.
When the number of calories we take in exceeds the number of calories we burn, weight gain results, we say. Eating too much and exercising too little causes weight gain, we say. Eating too many calories causes weight gain, we say. These “truths” seem so self-evident that we do not question whether they are actually true. But are they?
PROXIMATE VERSUS ULTIMATE CAUSE
EXCESS CALORIES MAY certainly be the proximate cause of weight gain, but not its ultimate cause.
What’s the difference between proximate and ultimate? The proximate cause is immediately responsible, whereas the ultimate cause is what started the chain of events.
Consider alcoholism. What causes alcoholism? The proximate cause is “drinking too much alcohol”—which is undeniably true, but not particularly useful. The question and the cause here are one and the same, since alcoholism means “drinking too much alcohol.” Treatment advice directed against the proximate cause—“Stop drinking so much alcohol”—is not useful.
The crucial question, the one that we are really interested in, is: What is the ultimate cause of why alcoholism occurs. The ultimate cause includes
•the addictive nature of alcohol,
•any family history of alcoholism,
•excessive stress in the home situation and/or
•an addictive personality.
There we have the real disease, and treatment must be directed against the ultimate, rather than the proximate cause. Understanding the ultimate cause leads to effective treatments such as (in this case) rehabilitation and social support networks.
Let’s take another example. Why does a plane crash? The proximate cause is, “there was not enough lift to overcome gravity”—again, absolutely true, but not in any way useful. The ultimate cause might be
•human error,
•mechanical fault and/or
•inclement weather.
Understanding the ultimate cause leads to effective solutions such as better pilot training or tighter maintenance schedules. Advice to “generate more lift than gravity” (larger wings, more powerful engines) will not reduce plane crashes.
This understanding applies to everything. For instance, why is it so hot in this room?
PROXIMATE CAUSE: Heat energy coming in is greater than heat energy leaving.
SOLUTION: Turn on the fans to increase the amount of heat leaving.
ULTIMATE CAUSE: The thermostat is set too high.
SOLUTION: Turn down the thermostat.
Why is the boat sinking?
PROXIMATE CAUSE: Gravity is stronger than buoyancy.
SOLUTION: Reduce gravity by lightening the boat.
ULTIMATE CAUSE: The boat has a large hole in the hull.
SOLUTION: Patch the hole.
In each case, the solution to the proximate cause of the problem is neither lasting nor meaningful. By contrast, treatment of the ultimate cause is far more successful.
The same applies to obesity: What causes weight gain?
Proximate cause: Consuming more calories than you expend.
If more calories in than out is the proximate cause, the unspoken answer to that last question is that the ultimate cause is “personal choice.” We choose to eat chips instead of broccoli. We choose to watch TV instead of exercise. Through this reasoning, obesity is transformed from a disease that needs to be investigated and understood into a personal failing, a character defect. Instead of searching for the ultimate cause of obesity, we transform the problem into
•eating too much (gluttony) and/or
•exercising too little (sloth).
Gluttony and sloth are two of the seven deadly sins. So we say of the obese that they “brought it on themselves.” They “let themselves go.” It gives us the comforting illusion that we understand ultimate cause of the problem. In a 2012 online poll,1 61 percent of U.S. adults believed that “personal choices about eating and exercise” were responsible for the obesity epidemic. So we discriminate against people who are obese. We both pity and loathe them.
However, on simple reflection, this idea simply cannot be true. Prior to puberty, boys and girls average the same body-fat percentage. After puberty, women on average carry close to 50 percent more body fat than men. This change occurs despite the fact that men consume more calories on average than women. But why is this true?
What is the ultimate cause? It has nothing to do with personal choices. It is not a character defect. Women are not more gluttonous or lazier than men. The hormonal cocktail that differentiates men and women must make it more likely that women will accumulate excess calories as fat as opposed to burning them off.
Pregnancy also induces significant weight gain. What is the ultimate cause? Again, it is obviously the hormonal changes resulting from the pregnancy—not personal choice—that encourages weight gain.
Having erred in understanding the proximate and ultimate causes, we believe the solution to obesity is to eat fewer calories.
The “authorities” all agree. The U.S. Department of Agriculture’s Dietary Guidelines for Americans, updated in 2010, forcefully proclaims its key recommendation: “Control total calorie intake to manage body weight.” The Centers for Disease Control2 exhort patients to balance their calories. The advice from the National Institutes of Health’s pamphlet “Aim for a Healthy Weight” is “to cut down on the number of calories . . . they get from food and beverages and increase their physical activity.”3
All this advice forms the famous “Eat Less, Move More” strategy so beloved by obesity “experts.” But here’s a peculiar thought: If we already understand what causes obesity, how to treat it, and we’ve spent millions of dollars on education and obesity programs, why are we getting fatter?
ANATOMY OF AN EPIDEMIC
WE WEREN’T ALWAYS so obsessed with calories. Throughout most of human history, obesity has been rare. Individuals in traditional societies eating traditional diets seldom became obese, even in times of abundant