Here is a question to chew on the next time you sit down for a meal: how much control do you really have over what you are eating?
In his new book, “Fat Chance” Dr. Robert Lustig argues that the answer is “not much.” He provides compelling evidence that our overall food consumption is determined by a complex suite of hormones that will drive us in ways that leave very little room for personal decision. This is because eating and drinking are inextricably bound up with the simple evolutionary drive to survive. And if your body believes that it is starving, it will compel you to eat – often and in great quantity. The key is in the phrase “if your body believes it is starving,” which we will return to in a moment.
The current framework for discussions of obesity assumes that the cause is simply that people, having plenty of food available, just eat too much for reasons of personal weakness or lack of willpower. According to this line of reasoning, thin people are virtuous and self-disciplined while overweight people are simply gluttonous. If they simply chose to eat less or to eat less “fatty” food, they’d be thin too. As Lustig argues, however, this view of obesity is almost certainly wrong.
To make his point, Lustig goes into great detail about the hormonal pathways that signal both hunger and satiety. As an endocrinologist, Lustig works with children that have had trauma to a part of the brain, the ventromedial hypothalamus (VMH), that acts as a master controller of nutrient metabolism. In particular, damage to the VMH can disable the pathways that accept a signal that we have eaten enough. Without the satiety signal, only the hunger signal remains.
It makes no sense to argue about “self control” or gluttony in the children under Lustig’s care: how much “discipline” do you expect from a six month old baby? His patients gain massive amounts of weight because their brain is continuously signaling to them that they are starving. They eat because they believe – no less than someone who is truly starving to death – that they will die without more food.
With this foundation established, the rest of the book describes how these insights apply to people that do not have structural damage to the brain. In particular, Lustig describes how the brain’s ability to respond to satiety signals is often severely compromised in the obese. This isn’t because of some congenital defect but rather due to the continuous consumption of low-quality, sugar-laden food. Not only does continuous over-consumption of fructose (a component of sugar and high fructose corn syrup) spike insulin and affect satiety signaling, the sweetness in sugar also has addictive qualities that make it very hard to resist in its own right.
“The quality of what we eat determines the quantity. It also determines our desire to burn it.”
To sum the position: much of our modern diet is laden with a substance, sugar, which holds a near-addictive appeal. Building the heavy use of sugar into the foundations of our food environment has resulted in a huge increase in the number of people with damage to their metabolic hormone systems that results in overeating. The people who overeat due to this damage are not “gluttonous” in a moral sense – they are simply responding to signals that they are, quite literally, starving to death.
Lustig goes to some length as well to demonstrate how, despite the presence of fructose in fruits, a more natural diet does not cause the problems found in processed foods. In particular, the fructose found in fruit is suspended in a matrix of soluble and insoluble fiber. Extracting the fructose requires work by the digestive system: work that slows down the rate of absorption and significantly blunts the ill effects of fructose. What we do by processing our foods is to strip out that fiber, extracting and concentrating the fructose. One take-away of his discussion of processing is that juice should in no way ever be considered a “healthy” drink. A glass of orange juice, for example, contains more sugar than a can of cola! Lustig reserves some of his most blistering criticism for the companies that market boxes of juice to children with labels implying that it is natural and healthy when it clearly is not (remember that Lustig has worked primarily with children). In essence, he argues, juice is poison for developing metabolic systems masquerading in a guise that appeals to caring parents.
In the last section of Lustig’s book, Dr. Lustig makes an often emotional appeal to fix the broken food environment, primarily through government regulation. Of course, he recognizes that much of the fault for the current environment lies with prior government policies (corn and sugar subsidies, the “low fat” recommendations from the USDA) but he argues strongly that the environment won’t change without top-down regulation.
Lustig’s book is a milestone in the discussion of obesity. Together with Gary Taubes, Lustig is standing the entire field of nutrition on its head. It is simply no longer credible to argue that the problem with Western diets is too much fat or that obesity is simply a matter of “eating too much and exercising too little.” We have created a toxic food environment and now blame the victims for falling prey to its appeal.
Lustig and Taubes will also, I hope, put a nail in the coffin of “nutritionism” – the belief that there are magic substances or foods that “make one thin” or healthy. If you have read my piece “On Weight and Diet” you know already our perspective on nutritionism. So it is encouraging to see that Lustig’s primary conclusion with respect to diet is simply “eat real food, minimally processed.”
With all of that out of the way, the primary disagreement that I have with Lustig – and that most reviewers have had – is that he places a bit too much faith in a top-down approach to the food environment. It is just too easy for the large food processors to influence policy through “regulatory capture” – the placement of people defending their interests on government regulatory agencies. While I believe that we should make every effort to lobby for saner agricultural policy, my personal sense is that a strong grass-roots effort to build understanding of the role of the food environment is likely to play an essential role as well.