Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity and Disease.
by Robert H. Lustig, MD
In this 2012 full-length book follow-up to his 2009 YouTube sensation, Sugar: The Bitter Truth, Dr. Robert Lustig describes how increased consumption of sugar has paralleled a steep rise in obesity and metabolic disease (diabetes, heart disease, cancer and dementia) over the last thirty years, amid dietary recommendations to eat less fat and cholesterol (and therefore more carbohydrates). He claims that the answer to the epidemics of obesity and metabolic disease lies in understanding the biochemical and physiological effects of our increased consumption of sugar, and offers his recommendations for how to address these problems.
In perhaps the strongest aspect of his book, Lustig deconstructs one of the most pervasive, and possibly damaging health misconceptions of our time: a calorie is a calorie. If this were true, then he says it would also be true that, “If you eat it, you better burn it, or you will store it.” According to this logic, it makes sense that the behaviors of gluttony (overconsumption of calories) and sloth (too little exercise) should cause obesity, and decades of diet advice have assumed that this is a proven, fundamental truth.
Lustig refutes this idea by devoting a large section of the book to describing the neurophysiology of the ventromedial hypothalamus (a part of our brain that controls how our body responds to hunger and feeding). He explains how our fat tissues signal to our brain that our body is well-fed via the hormone leptin. After eating, leptin causes feelings of satiety (we feel full), and signals our metabolism to speed up and burn energy. Conversely, when the leptin signal disappears, our metabolism slows to conserve energy, and we feel hungry.
Lustig describes how a high insulin level blocks the leptin signal. Interfering with our leptin signal both slows our resting energy expenditure, and also tricks our brain into signaling the “hungry” state, even when we have eaten. He describes that the linchpin of his argument is the hormone insulin, which is secreted after eating carbohydrates, and is the main hormone promoting fat and glucose storage in our adipose (fatty) tissue. By Lustig’s argument, a high insulin level triggers overconsumption of calories, but it also slows our metabolism, so that we burn fewer calories. His focus on the role of the brain in controlling our physiology and feeding behavior stems from his research interest in leptin signaling, but he does not completely describe what he means when he says that a calorie is not a calorie.
In his description of the possible ways in which hormones drive the behaviors of gluttony and sloth, Lustig avoids confronting the role of refined glucose-containing carbohydrates (starches) in promoting obesity. In spite of his own description of insulin being the linchpin of his argument, he completely ignores the well documented observation that any carbohydrate that raises insulin also promotes fat accumulation. As Gary Taubes has reviewed very convincingly in his book, Good Calories, Bad Calories, insulin has been shown to cause obesity even in undernourished individuals! Taubes’ hypothesis is that foods that raise insulin cause all food calories to be stored as fat, at the expense of the energy needs of the other tissues. His emphasis is that those starving tissues are what signal the brain to stimulate hunger and feeding behaviors, rather than the other way around. In Fat Chance, Lustig never returns to make a conclusion about what he actually means when he says that a calorie is not a calorie.
It is important to keep in mind that in the context of the Western diet, the degree to which starchy carbohydrates cause obesity or may contribute to metabolic syndrome has not been determined. Carbohydrates have been an integral part of the diet of many traditionally living cultures around the world, without causing metabolic syndrome. For example, carbohydrates from fruits, tubers, potatoes, honey and grains have provided a significant portion, or even in certain cultures (or seasons) the vast majority, of the caloric needs.
However, from a metabolic perspective, there are important differences from our modern cuisine. First, and perhaps most important, no traditional cultures utilized highly refined carbohydrates such as white flour or sugar, which are devoid of most or all of the nutrients that their unrefined sources contained. Cultures that have relied upon grains have traditionally also used methods of preparation, such as soaking and fermenting, that reduce the presence of toxins and anti-nutrients contained in the whole grain. Most traditionally utilized carbohydrate foods contain large amounts of fiber, which as Lustig also argues, slows the digestion of carbohydrates in the body. Lustig’s metabolic argument about fructose toxicity (and the possible role of the accompanying glucose) hinges upon the speed with which liquid sugar or fructose hits the liver, and fiber slows this process and reduces the corresponding insulin release. In the extreme example of bingeing on honey or fruit as a sole source of calories, it would be expected that significant weight would be gained from the resulting spike in insulin. However, since large quantities of fruit or honey would most likely have occurred seasonally, the metabolic state would also change once the season changed, with subsequent periods of low insulin allowing the body to burn off the excess stored energy and return to its natural body fat composition. In the typical Western diet, sugar is available year-round, and even between every meal. In this situation, the high insulin state would be expected to drive long-term weight gain and other metabolic disturbances that Lustig has described as the toxic effects of fructose.
After introducing the concept of hormones driving our caloric intake and resting energy expenditure, Lustig describes different aspects of our modern lifestyle that rewire our energy metabolism in this way. He describes the prevalence of processed and fast food in the standard American diet, and the replacement of fat by sweeteners. He spends a chapter describing the properties of sugar that qualify it as an addictive substance. Each chapter of the book begins with a clinical vignette describing some of his UCSF childhood obesity clinic patients’ health conditions, which illustrate various aspects of his book topics. For example, one concerns the hunger of an eight-year-old girl diagnosed with type 2 diabetes, and another an obese eight-year-old boy whose father brought home unlimited quantities of juice from his job.
Eventually Lustig describes fructose metabolism, and the ways in which it promotes metabolic syndrome. He states that sugar and high-fructose corn syrup are metabolized exactly the same in our bodies, so are effectively equivalent sources of fructose. He has written a very understandable description of the known metabolic effects of fructose (including liver inflammation and insulin resistance, chronic rise in insulin levels, high blood pressure, fatty liver, cancer, and more). These effects of fructose are significant because they challenge the widely held assumption that fat causes heart disease.
One of Lustig’s most important contributions from his YouTube lecture was his description of the role of two different kinds of LDLcholesterol in heart disease. Many people think of LDL as being the “bad” cholesterol, but he explains beautifully in his lecture that one type of LDL is small, dense and able to slip under the edge of the cells lining our blood vessels and initiate atherosclerotic plaques that lead to heart disease. This small, dense LDL-cholesterol is caused by eating carbohydrates. The other type of LDL-cholesterol is large and buoyant, and does not cause heart disease. This is the type of LDL that increases after a meal containing saturated animal fats. So, while some evidence shows that the total LDL-cholesterol level does correlate with death rates from cardiovascular disease, it is now well understood that this is due to eating carbohydrates, not fat!
Lustig argues that fructose is much more potent than glucose at raising the levels of small dense LDL. However, his critics have pointed out that the degree to which this is true in humans has not been proven. The idea that sugar could be the cause of metabolic syndrome and heart disease represents a complete paradigm shift from our decades of assumption that eating fat causes heart disease. Although this represents one of Lustig’s most significant contributions from his lecture, the point was only briefly mentioned in his book.
One of my fundamental criticisms of the book is that although he vilifies sugar, Lustig claims that eating sugar is specifically bad because it is both carbohydrate (glucose) and fat (fructose) at the same time. His logic here is very vague, and contradicts his prior statements that fructose (and its metabolic effects) are distinctly different from those of fat. To say that fructose is fat is certainly not true, and when he equates fructose with fat, it perpetuates the last thirty years of nutrition and medical advice that have led to our present state of health. It may be that eating glucose with fructose can make the effects of fructose worse by raising insulin levels, but to me this would implicate carbohydrates, not fat, as the cause of metabolic disruptions.
This example brings me to another general criticism of his book. The style and organization are confusing, and most of his claims are spoken as truth without supporting evidence. One frustrating example was for his chapter on fructose, when he describes how fructose in the liver is metabolized to excess acetyl-CoA, which is converted into fat that can promote heart disease. His description did not clarify what type of fat is formed or how that fat promotes heart disease, but did refer to his chapter on metabolic syndrome. I flipped to that section of the book, but acetyl-CoA is not mentioned at all in that chapter, and the sections referring to how an overburdened liver exports fat referred back to the chapter where I started. I found this type of circular logic in many places in the book.
After describing how fructose is a toxin, the second half of Lustig’s book reaches beyond his area of expertise in metabolism and neuroendocrinology into recommendations for personal and public health solutions to the obesity epidemic. In this part of the book, he speeds through descriptions of possible strategies for eating that have been proposed as solutions to obesity and disease, such as Atkins, vegan, traditional Japanese, Mediterranean, Ornish, and Paleolithic. All of these diets restrict the intake of sugar.
To his credit, in one chapter he does describe several good examples of how humans are perfectly evolved to eat fat, which he calls the “hunter” lifestyle. However, he dismisses a low-carb, high-fat “paleolithic” diet as “too expensive.” It was disconcerting to read his contrasting comments about a vegan diet, which he calls the “gatherer” lifestyle (all carbohydrates). He states that a vegan diet (even a “fruitarian” diet!) can be perfectly healthy, and is practiced with success by multiple cultures around the world. Here is where I was hoping that he would combine existing knowledge into a strategy for eating that keeps our metabolism running, reduces inflammation, and helps our hunger/ reward hormone system work well. However, he does not recommend a dietary strategy.
From Lustig’s description of our physiology, it is easy for me to see how a sugar-free diet could help prevent metabolic syndrome. This advice may be enough to improve the lives and health of the large portion of the population that has metabolic syndrome, but he does not describe or justify a dietary strategy for optimal health. Instead, he ends with the underwhelming advice to simply cook your own food.
For a public health solution Lustig is an advocate for cutting sugar out of processed food. He briefly outlines the roles of government programs such as SNAP and WIC, the FDA and USDA, and the Farm Bill in promoting overconsumption of sugar. His view is that a lawsuit against the FDA to remove fructose from its Generally Regarded As Safe (GRAS) list would be the only way to force food manufacturers to reform, but that it is politically untenable (after all, it only took about one hundred years of eating trans fat before the FDA removed it from the GRAS list just last year). He obviously believes that speaking out about the toxicity of sugar is important for swaying public awareness, and that the way to force change is through lawsuits that will not happen until massive numbers of people begin to pressure politicians to support such maneuvers. Notably, the FDA has just this year proposed changing the Nutrition Facts label on food products to include a line for added sugars, and to eliminate the line for percent calories from fat. So, it is possible that changes in awareness about the effects of sugar have already percolated through the ranks of the health and nutrition authorities.
I am not sure how to “digest” the take-home message that federal regulations on sugar are the solution to chronic disease. Although restrictions on sugar would force changes in the processed food industry that would be high-impact because so many people depend upon it, this approach still perpetuates a processed- and fast-food culture that cannot provide healthy, nutrient-dense food. It is a disaster that we depend so heavily upon industrial agriculture for advice on diet and health rather than upon the traditions of our cultural wisdom.
Understanding how sugar can be toxic to our health is an important goal, and this book does describe well the shocking metabolic effects of fructose. However, Dr. Lustig’s diet advice unfairly blames fat, and he has not reconciled his concept that a calorie is not a calorie with the known role of refined carbohydrates in causing obesity. Overall, his claims are presented without evidence, and the book does not provide a fundamentally new solution. Take ninety minutes to watch the YouTube lecture, but I give the book a disappointed Thumbs Down.
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly journal of the Weston A. Price Foundation, Spring 2014.