44 pages • 1 hour read
Jason FungThe Obesity Code: Unlocking the Secrets of Weight Loss
Nonfiction | Book | Adult | Published in 2016A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Part 2Chapter Summaries & Analyses
Part 2: “The Caloric Deception”
Part 2, Chapter 3 Summary and Analysis: “The Calorie-Reduction Error”
Chapter 3 focuses on the fallacy of the “calories in, calories out” theory of weight loss. Experiments reveal that the body compensates for extreme caloric reduction by expending less energy. The subjects of the Minnesota Starvation Experiment of 1945, for example, experienced a decrease in resting metabolic rate and a drop in body temperature in response to caloric deprivation (37). Their blood pressure and physical endurance also dropped. The psychological effects were equally striking: the subjects were unable to concentrate, experienced constant hunger, and became disinterested in everything, save food. In short, their bodies adapted to caloric reduction by reducing expenditure. Adaptation started with a rapid drop in body fat. After the experiment ended, however, the subjects regained weight quickly until they were heavier than they were at the outset.
Caloric-reduction diets are comparable to the Minnesota Starvation Experiment. Dieters lose weight by eating less, prompting their metabolisms to slow, which leads to a plateau in weight loss and eventually to weight gain. A 2006 National Institutes of Health study of 50,000 post-menopausal women conclusively undermined the approach to weight loss. A third of the women followed a low-fat diet, participated in educational sessions, and were encouraged to exercise. A control group was told to eat as they normally did and received minimal educational support. The “Eat Less, Move More” group initially lost weight, but eventually regained it. By the end of the study, there were no significant differences between the two groups. The study confirmed what doctors have known for decades: that caloric reduction only results in temporary weight loss. Despite numerous studies, however, the “Eat Less, Move More” movement is as strong as ever. Dieters blame themselves for failing to lose weight when the problem lies with the approach.
Studies show that the body adapts to caloric reduction not just by reducing expenditure, but also hormonally. For example, weight loss increases ghrelin levels, a hormone that triggers hunger. Further, low-fat diets impact satiety hormones, such as peptide YY, cholecystokinin, and amylin, making dieters feel less full. Increased hunger, combined with decreased satiety, raises the desire to eat. Like metabolic decreases, these hormonal changes are both immediate and persistent. Fung describes under-eating as a “vicious cycle” (46). Dieters reduce their caloric intake as their bodies adapt to starvation, doubling down on their efforts until the cycle becomes intolerable. Once they break, the old weight comes back, and then some. Despite its inefficacy, health authorities continue to promote caloric reduction as the path to lasting weight loss, essentially blaming people for gaining weight when the problem lies in false information and faulty tools.
Part 2, Chapter 4 Summary and Analysis: “The Exercise Myth”
Chapter 4 examines the connection between exercise and weight loss. Concerns about heart disease in the 1950s led healthcare professionals and government officials to hail the virtues of exercise as a prime way to lose weight. An exercise industry emerged as people embraced active lifestyles. Exercising, however, does not translate to lower obesity rates, as evidenced by statistics. Countries with low exercise rates, like the Netherlands, have lower obesity rates than those with high exercise rates, like the US. Conventional wisdom holds that exercise rates have decreased since hunter-gatherer times and that sedentary lifestyles led to obesity. However, the research shows that obesity rates have increased alongside exercise rates, especially from the 1980s to the mid-2000s (51).
Studies reveal that exercise has a minimal effect on weight loss. A 2007 survey found that women who do aerobics six days per week only lose an average of 3 pounds over the course of a year, while men lose an average of 4 pounds (54). According to the 2010 Women’s Health Study, a 10-year study of nearly 40,000 women, intense exercise leads to no weight loss (54). One explanation is a phenomenon called compensation: People tend to eat more after rigorous exercise. People who exercise are also less likely to be active during the rest of the day. Indeed, a 2009 study revealed that children who take physical education classes at school do the same amount of physical activity per week as children who take no classes. Fung provides an abysmal assessment of current approaches to weigh loss with an unvarnished analogy: “We are writing a final examination called Obesity 101. Diet accounts for 95% of the grade and exercise for only 5%. Yet we spend 50% of our time and energy studying exercise. It is no wonder that our current grade is F—for Fat” (56).
Part 2, Chapter 5 Summary and Analysis: “The Overfeeding Paradox”
Chapter 5 focuses on the unexpected results of overeating experiments. The caloric reduction theory of weight loss holds that overeating necessarily results in weight gain. However, studies show that the types of foods one ingests matter far more than the total number of calories. Overeating carbohydrates results in weight gain, whereas overeating proteins and fats does not. Additionally, the metabolism increases in response to overeating. Although weight gain can occur, it tends not to last (just as undereating does not result in lasting weight loss). Overeating studies consistently show that increased caloric intake leads to increased expenditure. Fung surmises that if excess calories do not cause obesity, then cutting calories won’t result in weight loss.
Homeostasis is a biological principle describing the body’s tendency toward equilibrium. If a person’s weight drops below its set point, the body will compensate to raise it. For obese people, the set point is too high. The compensating mechanisms are largely hormonal. The appetite hormone (ghrelin) increases when body weight decreases below the set point. Similarly, weight loss suppresses the satiety hormones (peptide YY, cholecystokinin, and amylin). The metabolism also slows in response to weight loss: Heart rate slows, body temperature and blood pressure drop, and the heart volume decreases to conserve energy. Overeating spurs similar hormonal responses. The body will briefly gain weight before activating weight loss mechanisms by decreasing appetite. The metabolism will also increase to burn excess calories. Rather than fight obesity with diet and exercise, Fung recommends finding ways to lower the homeostatic mechanism. He identifies leptin as a key hormonal regulator. Most obese people have high levels of leptin. They are also leptin resistant. Finding a treatment for leptin resistance, then, is key to fighting obesity.
