The Obesity Code. Jason Fung

so movement was reduced. Result: weakness during physical activity.

      •Calories are needed to replace hair and nails. Fewer calories were available, so hair and nails were not replaced. Result: brittle nails and hair loss.

      The body reacts in this way—by reducing energy expenditure—because the body is smart and doesn’t want to die. What would happen if the body continued to expend 3000 calories daily while taking in only 1500? Soon fat stores would be burned, then protein stores would be burned, and then you would die. Nice. The smart course of action for the body is to immediately reduce caloric expenditure to 1500 calories per day to restore balance. Caloric expenditure may even be adjusted a little lower (say, to 1400 calories per day), to create a margin of safety. This is exactly what the body does.

      In other words, the body shuts down. In order to preserve itself, it implements across-the-board reductions in energy output. The crucial point to remember is that doing so ensures survival of the individual in a time of extreme stress. Yeah, you might feel lousy, but you’ll live to tell the tale. Reducing output is the smart thing for the body to do. Burning energy it does not have would quickly lead to death. The energy budget must be balanced.

      Calories In and Calories Out are highly dependent variables.

      With reflection, it should immediately be obvious that caloric expenditure must decrease. If we reduce daily calorie intake by 500 calories, we assume that 1 pound (0.45 kilograms) of fat per week is lost. Does that mean that in 200 weeks, we would lose 200 pounds (91 kilograms) and weigh zero pounds? Of course not. The body must, at some point, reduce its caloric expenditure to meet the lower caloric intake. It just so happens that this adaptation occurs almost immediately and persists long term. The men in the Minnesota Starvation Experiment should have lost 78 pounds (35.3 kilograms), but the actual weight lost was only 37 pounds (16.8 kilograms)—less than half of what was expected. More and more severe caloric restriction was required to continue losing weight. Sound familiar?

      What happened to their weight after the semi-starvation period?

      During the semi-starvation phase, body fat dropped much quicker than overall body weight as fat stores are preferentially used to power the body. Once the participants started the recovery period, they regained the weight rather quickly, in about twelve weeks. But it didn’t stop there. Body weight continued to increase until it was actually higher than it was prior to the experiment.

      The body quickly responds to caloric reduction by reducing metabolism (total energy expenditure), but how long does this adaptation persist? Given enough time, does the body increase its energy expenditure back to its previous higher level if caloric reduction is maintained? The short answer is no.¹¹ In a 2008 study, participants initially lost 10 percent of body weight, and their total energy expenditure decreased as expected. But how long did this situation last? It remained reduced over the course of the entire study—a full year. Even after one year at the new, lower body weight, their total energy expenditure was still reduced by an average of almost 500 calories per day. In response to caloric reduction, metabolism decreases almost immediately, and that decrease persists more or less indefinitely.

      The applicability of these findings to caloric-reduction diets is obvious. Assume that prior to dieting, a woman eats and burns 2000 calories per day. Following doctor’s orders, she adopts a calorie-restricted, portion-controlled, low-fat diet, reducing her intake by 500 calories per day. Quickly, her total energy expenditure also drops by 500 calories per day, if not a little more. She feels lousy, tired, cold, hungry, irritable and depressed, but sticks with it, thinking that things must eventually improve. Initially, she loses weight, but as her body’s caloric expenditure decreases to match her lowered intake, her weight plateaus. Her dietary compliance is good, but one year later, things have not improved. Her weight slowly creeps back up, even though she eats the same number of calories. Tired of feeling so lousy, she abandons the failed diet and resumes eating 2000 calories per day. Since her metabolism has slowed to an output of only 1500 calories per day, all her weight comes rushing back—as fat. Those around her silently accuse her of lacking willpower. Sound familiar? But her weight regain is not her failure. Instead, it’s to be expected. Everything described here has been well documented over the last 100 years!

       AN ERRONEOUS ASSUMPTION

      LET’S CONSIDER A last analogy here. Suppose we manage a coal-fired power plant. Every day to generate energy, we receive and burn 2000 tons of coal. We also keep some coal stored in a shed, just in case we run low.

      Now, all of a sudden, we receive only 1500 tons of coal a day. Should we continue to burn 2000 tons of coal daily? We would quickly burn through our stores of coal, and then our power plant would be shut down. Massive blackouts develop over the entire city. Anarchy and looting commence. Our boss tells us how utterly stupid we are and yells, “Your ass is FIRED!” Unfortunately for us, he’s entirely right.

      In reality, we’d handle this situation another way. As soon as we realize that we’ve received only 1500 tons of coal, we’d immediately reduce our power generation to burn only 1500 tons. In fact, we might burn only 1400 tons, just in case there were further reductions in shipments. In the city, a few lights go dim, but there are no widespread blackouts. Anarchy and looting are avoided. Boss says, “Great job. You’re not as stupid as you look. Raises all around.” We maintain the lower output of 1500 tons as long as necessary.

      The key assumption of the theory that reducing caloric intake leads to weight loss is false, since decreased caloric intake inevitably leads to decreased caloric expenditure. This sequence has been proven time and again. We just keep hoping that this strategy will somehow, this time, work. It won’t. Face it. In our heart of hearts, we already know it to be true. Caloric reduction and portion-control strategies only make you tired and hungry. Worst of all . . . you regain all the weight you have lost. I know it. You know it.

      We forget this inconvenient fact because our doctors, our dieticians, our government, our scientists, our politicians and our media have all been screaming at us for decades that weight loss is all about Calories In versus Calories Out. “Caloric reduction is primary.” “Eat Less, Move More.” We have heard it so often that we do not question whether it’s the truth.

      Instead, we believe that the fault lies in ourselves. We feel we have failed. Some silently criticize us for not adhering to the diet. Others silently think we have no willpower and offer us meaningless platitudes.

      Sound familiar?

      The failing isn’t ours. The portion-control caloric-reduction diet is virtually guaranteed to fail. Eating less does not result in lasting weight loss.

       EATING IS NOT UNDER CONSCIOUS CONTROL

      BY THE EARLY 1990s, the Battle of the Bulge was not going well. The obesity epidemic was gathering momentum, with type 2 diabetes following closely behind. The low-fat campaign was starting to fizzle as the promised benefits had failed to materialize. Even as we were choking down our dry skinless chicken breast and rice cakes, we were getting fatter and sicker. Looking for answers, the National Institutes of Health recruited almost 50,000 post-menopausal women for the most massive, expensive, ambitious and awesome dietary study ever done. Published in 2006, this randomized controlled trial was called the Women’s Health Initiative Dietary Modification Trial.¹² This trial is arguably the most important dietary study ever done.

      Approximately one-third of these women received a series of eighteen education sessions, group activities, targeted message campaigns and personalized feedback over one year. Their dietary intervention was to reduce dietary fat, which was cut down to 20 percent of daily calories. They also increased their vegetable and fruit intake to five servings per day and grains to six servings. They were encouraged to increase exercise. The control group was instructed to eat as they normally did. Those in this group were provided with a copy of the Dietary Guidelines for Americans, but otherwise received little help. The trial aimed to confirm the cardiovascular health and weight-reduction benefits of the low-fat diet.

      The average weight of participants at the beginning of the study was 169 pounds (76.8 kilograms). The starting