INTRODUCTION In the summer of 2001, most of my friends, like me, had just graduated from college. They had chosen to move to big cities, get fancy jobs, and spend their nights hanging out with friends and going to concerts--typical stuff for twenty-something-year-olds. I, on the other hand, had chosen a different way to spend my evenings. I spent them feeding rats. Let me back up for a minute and give you some context. I had started graduate school at Princeton University that summer. I arrived in Princeton with a huge case of imposter syndrome. Imposter syndrome is the psychological term used to describe the feelings that people can get when they think they don''t deserve to be someplace, and that at any moment someone is going to discover they are a fraud or an "imposter" and expose them.

(A topic for another book, I suppose.) No one in my family had ever even been to college, and here I was getting a PhD in neuroscience from an Ivy League school. I couldn''t help but feel that clearly, someone had made a mistake in letting me in. Despite the negative voices in my head, I resolved to push forward and do my best. I was assigned to work with a professor named Dr. Bartley Hoebel. His friends and students all called him Bart. He was a very tall (6"7"-ish), lean man, who had a quiet, gentle nature.

He was a true Ivy Leaguer, having trained at the University of Pennsylvania and Harvard, and was now a well-respected professor at Princeton. He was accomplished, with hundreds of published scientific papers on what happens in the brain in response to people engaging in motivated behaviors, like eating, drinking, using drugs, or mating. He was regularly invited to give presentations all over the world to discuss his latest research findings. I thought that his research was fascinating and felt very fortunate to be his student. One day that summer, Bart asked me to come to his office so that we could have a meeting to talk about what I might want to work on as a research project that I could eventually turn into a PhD dissertation. This had to be a big idea--something that I would work on for the next five years of my life. Little did I know I would still be working on it over twenty years later. We started to talk about how there was a lot of interest in the scientific community regarding obesity at the time, as there still is now, and media reports often mentioned rising obesity rates.

Keep in mind that the year 2001 was a while ago, and back then most people (including doctors) viewed obesity as being caused by a lack of willpower on the part of the individual, and essentially put all the blame on the person who was overweight or obese for being that way. We began thinking about how it was strange that, despite all the public health warnings concerning the dangers of being obese, and the multimillion-dollar diet industry that offered an array of choices and plans to follow to lose weight, people still couldn''t do it. The South Beach Diet®, the Zone Diet®, WeightWatchers®, the Master Cleanse®--these are just a few of the more popular options that many people tried and failed. They were being handed a plan, but it was impossible to stick to. Why? Could it all be about lack of willpower? And if, for argument''s sake, it was, what was causing people not to have the willpower to make healthier choices about what they ate? For some individuals who had obesity-related comorbid conditions, like diabetes or heart disease, this was a matter of life and death. It seemed like more than willpower was at play here. What if being overweight or obese had less to do with the person and their supposed lack of willpower, and more to do with what they were eating? Thanks to advancements in technology and agriculture, our food supply has continued to evolve. This is a good thing, as it has allowed us to avoid starvation and feed the increasing number of humans that inhabit the earth.

However, when we look at the changes that have occurred over the past fifty years, it seems that many of these changes are for the worse. More and more people are relying on fast food, processed grocery store foods, and vending machines as a staple in their diet. And there is a common thread among these foods: they all contain added sugar. Pour on the Sugar Sugar. It has been around for centuries, and for most of that time we have lived in harmony with it, but that suddenly is changing. I will get into this more in the next chapter, but back in the early 2000s, we were coming off the "low fat" diet trend that had begun in the 1970s. Fat had been demonized by the American Medical Association (AMA) and other important medical groups because of its supposed negative impact on heart health, and these groups also argued that it caused obesity. To break it down to sound bites for the media: If you eat fat, you will get fat.

Fat = bad, carbs = good. What started this idea? Back in the 1960s a physiologist named Ancel Keys published a theory that dietary fat raises cholesterol levels and gives you heart disease. This began a decades-long era in which all dietary fats were thought to be bad for your health. In the late 1970s, "Dietary Goals for the United States" was published, advising Americans to significantly curb their fat intake, and in 1984, the National Institutes of Health (NIH) officially recommended that all Americans over the age of two eat less fat. Turns out, they were all very wrong. But at the time, because the public had been sternly warned to avoid fats in fear that they would die from a heart attack or end up obese, most Americans were ditching the fats and, instead, eating more and more carbohydrates. This meant that in the 1970s we saw an influx of sugar in our food supply that slowly went up over time. You could see this for yourself when you went to the grocery store.

Aisles were lined with "low fat" cookies and snacks, and they all contained added sugars. If you lived through this time period, you may fondly recall SnackWell''s®, which were a popular brand of fat-free cookies and other treats. People were (falsely) led to believe that you could indulge guiltlessly on them, because they were labeled as "fat-free." Back then, it was fat that was bad for you, so companies were doing you a favor by taking it out of the products. The problem was that if you take the fat out, the food usually tastes terrible. So the food companies added sugar to make it taste good again. Sugar is a carbohydrate, so it was safe, and heck, better for you than the dreaded fat! All the while in the background, it was becoming apparent that sugar might not be all that good for us. Sweets were usually--and still are--the main topic of discussion when people wanted to lose weight.

Many people for years had been talking about how they craved sugar, had a sweet tooth, and if they were trying to lose weight, giving up the white stuff was the hardest part. Sugar seemed to be a barrier for many people, and it stood in the way of losing weight. Giving up desserts and sweets was usually the tactic to try to lose weight, and usually the downfall for most dieters because it was hard to stick to. In the latter part of the 1990s another shift occurred. The media had begun to take note of America''s inability to give up the white stuff. You could pick up any magazine at the grocery checkout at that time and read a headline about "being hooked on carbs" or "ways to beat your sweet cravings." Mass media hinted that people were hooked, in some way, on sugars and carbohydrates. Were these just sensationalized headlines to grab readers, or was there actually something to this idea? I started to look more carefully at some of the processed food products that were on the market--many contained so much added sugar, and in amounts that we would never ever see in nature.

As a neuroscience student, I knew that the parts of the brain that evolved to regulate our appetite were used to concentrations of sugar that were more like what you would find in nature--for example, in an apple. But now, our brains were being blasted multiple times each day with the effects of ten times that amount of sugar from cookies, cakes, and protein bars. Not to mention all the sugar-laden foods that people were eating because they thought they were healthy, like some yogurts, salad dressings, and even fruit smoothies. It reminded me of what happens with drugs like heroin and cocaine. Part of the reason drugs like these are so addictive is because they over-activate the brain reward centers (more on this in chapter 3). They hijack the reward system and set our pleasure into overdrive. Drugs make you feel good (at first, at least), and our brain adapts accordingly to make us crave that feeling again and again, which makes us do almost anything to get it. I started to ponder: What if these processed foods that were so commonplace in our society, with loads of added sugar, were hijacking our brains in the same ways that drugs of abuse do? Could people be hooked on sugar in the way people get "hooked" on other things, like drugs and alcohol? Could people actually get addicted to sugar? After our initial discussion, Bart asked me to look into the scientific literature to see what I could come up with about sugar addiction as a basis for my dissertation.

Excited to prove how great a student I was and to confirm to my inner monologue that Princeton was correct to admit me, I went off to the library to put together a literature review to discuss at our next meeting.