Summary: Don't let anyone tell you there is only ONE factor driving obesity (sugar, fat, insulin, sedentary behavior, etc.) because there are many. But take heart, understanding the complexity can help us take better control of our eating behaviors, our health, and maybe inspire a little self-compassion. This one's on me for being so late. Stephan Guyenet, PhD's book "The Hungry Brain" was published in February and I am reviewing it now. But don't be like me, get this book NOW if you haven't.
"If our eating behavior is primarily guided by conscious choices based on rational thinking, then educating the nation on what to eat should be a highly effective way of making us slimmer and healthier over time... In contrast, if our everyday eating behavior is primarily guided by brain systems that aren't so rational, information alone shouldn't be a very effective way to change it, no matter how accurate, clear, and compelling it is." (pg 3)
- Stephan Guyenet, PhD, The Hungry Brain
I'll get to the point: This book is good
I strongly believe "The Hungry Brain" is REQUIRED READING for nutrition enthusiasts
In fact, I think this book is a necessary addition to a nutrition class syllabus and to the libraries of anyone who practices or works with populations trying to manage weight: RDs, MDs, personal trainers, everyone. Interested in a free copy? I am doing a drawing on my Instagram, check it out at the bottom of the review!
Why? Unlike most diet books that attempt to distill a complex problem into a simple one with a single solution, Stephan Guyenet takes a measured and scientific approach to the neuroscience of obesity. And despite having practical tips for weight loss and healthy eating, it is not a "diet book." Not only does he make a scientific case for his point of view regarding neuro-regulation of appetite, but he includes the detailed and fascinating history surrounding appetite, satiety, and overeating.
This isn't surprising considering Guyenet's background as an actual scientist. Unlike many weight-loss focused books (which can be written by anyone with any or no expertise), Guyenet is an expert in his field. With a PhD in neurobiology, it's clear from the writing that he knows the topic inside and out and he's passionate about it. For those who are't familiar with Guyenet, you can see his blog here.
What's the book about?
In Guyenet's own words: "In this book, I'll argue that overeating and obesity are caused by a mismatch between ancient survival circuits in the brain and an environment that sends these circuits the wrong messages." (pg 5)
Guyenet has long been a mainstay of the paleo diet community and in my opinion, this book really nicely emphasizes the strong points of the paleo diet heuristic while dismissing the more mythological aspects of paleo. Namely, there is strong evidence that the modern food environment encourages overeating - a tenet of the paleo diet encourages eating whole, non-processed foods - but there is less strong evidence for some of the nutritional tenets of paleo, like eschewing potatoes or legumes. (Yes, I realize there are varying shades of paleo, but go with me on this journey.)
The writing is clear and the science is well-explained, but don't expect Guyenet to dumb it down for a lay audience. The history of scientific progress in weight regulation as well as the experiments and observations that inform his conclusions are meticulously described.
The downside is that this book requires that you concentrate a little bit.
The upside is that Guyenet isn't trying to sell you on tenuous principles; everything he claims is cited and explained to the nth degree.
In fact, I think we should require that all diet books contain this level of detail. If the author can't explain every mouse study supporting (or not supporting) his or her position, maybe they aren't expert they're purporting to be?
The main points:
The book is split up into 11 chapters, each of which explores a different aspect of how humans came to be so good at overeating. In the beginning, he focuses on the development of the brain and how humans make sophisticated food choices, and how food reward affects those choices. Then, he goes into how appetites are stimulated and satiated and the hormonal aspects of hunger regulation. Finally, he delves into how our brains, our hormones, and therefore our appetites are affected by a modern environment plagued with constant low-level stress and sleep disruption. The final chapter deals with how to outsmart the evolutionary hand we've been dealt when it comes to foods.
Guyenet makes several key points:
1. We can't blame a single nutrient, or even a single cause. In Guyenet's point of view, with which I am inclined to agree, simplifying the "obesity epidemic" to a single flashpoint (like the 1980 dietary guidelines) is as misguided as blaming all weight gain on "lack of self control."
In Chapter 4, Guyenet directly addresses the single nutrient theories for explaining obesity:
"In popular media, there is a perennial debate over whether sugar or fat is responsible for the obesity epidemic. This has led some people to view obesity research as a team sport rather than a scientific discipline. Allow me to end the debate by stating what most researchers find quite obvious: It's both. In particular, the combination of concentrated sugar and fat in the same food is a deadly one for our food reward system. It's also a pairing that rarely occurs in nature..." (pg 79)
I have to admit, I drew a smiley face next this quote. If only one statement could end that endless, tired debate! Wishful thinking indeed, but yes, I agree. Let's end this debate!
2. There are biological reasons for overeating. From an evolutionary standpoint, food has historically been scarce and mechanisms that increase appetite and allow humans to eat more than they need is protective. Guyenet goes into detail describing observational work done in modern hunter-gatherer tribes including the !Kung, Yanonmamo, and Hazda and detailing how the bulk of their labor is devoted to obtaining enough food. Additionally, Guyenet notes that these people, as well as ancestral hunter gatherers, spend large percentages of their lives hungry.
He notes that nonindustrial diets share three factors in common: Limited variety, limited ability for processing, and few cooking methods. These aspects limit how enjoyable meals can be, but also limit total caloric density and intake. Further, he points out that the baseline hunger most hunter-gatherers experience mean that "Gluttony is good for them," and that this tendency likely exists for humans in the industrial food environment as well, where "We try to use the sophisticated tools of our cognitive mind to restrain our impulses to overeat..." and as you know, "...the impulses often win." (pg 97)
3. Palatability: The availability and palatability of highly processed foods has contributed significantly to our current problems with high body weight. This is not because there is a single input (fat, sugar, pesticides, etc) that contributes to the problem, but because the combinations of nutrients and salt are so tasty, they can override the brain's satiety signals and cause people to overeat without realizing it. Guyenet presents a strong case that this happens in humans as well as in rats.
"The most highly palatable foods tend to be dense in easily digested calories and combine multiple innately preferred food properties in highly concentrated form..." (pg 58) Significant research, Guyenet puts forward, shows that people instinctively increase their intake with meals they find to be highly rewarding. And, not surprisingly, a variety of highly rewarding foods further enhances that effect. In fact, human studies have shown that people with obesity who have unlimited access to a single food source with no variability and little food reward lose weight rapidly. Perhaps unsurprisingly, studies also show that tendencies to overeat highly palatable foods vary between individuals.
4. High stress, low sleep environment: Constant stress caused by news, work, and other life issues exacerbates the effects of the high-palatability food environment. Ditto short sleep. In fact, Guyenet points out compelling evidence that while stress typically reduces intake when primates are presented with plain foods, it increases intake when highly palatable foods are available. And this is fairly consistent when it comes to humans as well.
"Human studies were showing that stress doesn't just change the amount of food we eat; it also markedly alters the types of foods we eat. Depending on how you're wired, calorie intake can go up or down during stress, yet regardless of this, most of us gravitate toward calorie-dense "comfort foods" like chocolate, ice cream, macaroni and cheese, and pizza." (pg 212)
Disrupting the circadian rhythm? Yeah, it can also negatively impact your eating habits.
5. Hormones: Guyenet includes a fascinating description of the history of the discovery of leptin (very much drama!) as well as the breeding of strains of obese mice frequently used to do nutrition and weight research. In addition, he looks specifically at people who have rare genetic mutations that cause obesity, and the results of studies on humans who have lost large amounts of weight.
In his breakdown of the body of science surrounding weight gain, weight loss, and the body's weight "set point," Guyenet makes conclusions that are both uplifting and, well, depressing.
"The findings... lead us inescapably to the conclusion that appetite and adiposity are, to a large extent, biological phenomena that are regulated by nonconscious parts of the brain. Their research [multiple scientists in this field] has brushed away a variety of archaic hypotheses... and left us with a clear understanding that food and adiposity are not simply the result of conscious, voluntary decisions." (pg 130)
The good news? We can and should stop letting people believe they have no "self control" if they struggle with weight.
The bad news? "...once a person develops obesity, it becomes a self-sustaining state and the person has to overeat to feel the same satisfaction that a lean person feels after eating a smaller meal." (pg 134)
But, there is hope!
In an effort to keep out spoilers, I've left out Guyenet's solutions for how individuals can adjust for factors that make weight loss and balanced eating such a hard task! In the book, they're placed in gray pull-out boxes that give you the practical take away from each chapter with to-dos that can help you adjust your eating habits to optimize your diet and weight.
The final chapter of the book, titled "Outsmarting the Hungry Brain" condenses these tips into six steps you can use to make better food choices and avoid typical eating pitfalls. Though the advice isn't entirely novel, by the end of the book you have a strong understanding of what drives your motivation to make poor food choices in each of the situations Guyenet lays out.
In his words, "The good news is that the lipostat [your brain's "thermostat-like" tendency to maintain your body weight at the highest point] responds to the cues we give it through our diet and lifestyle, and we can use this to our advantage."
That background knowledge make the tips feel especially useful - In fact, I brainstormed extremely specific ways to put these into action. Interested in knowing them? Leave a comment saying so and perhaps I'll put a blog post together on it!
Ultimately, Guyenet posits that the only way to tackle the "obesity epidemic" as a society is to make environmental changes that will nudge people toward making healthier choices day-to-day (not totally unlike the conclusions made by Dr. Gibney in Ever Seen a Fat Fox). My inclination is to agree, since the population reading technical nutrition books is extremely self-selected. In order to get the general public making healthy food choices regularly, we need to make some systemic changes.
In the meantime, for those of us who read this book, there are easy, practical, and evidence-based changes we can make right now.
WIN A COPY OF "THE HUNGRY BRAIN"!
No, you can't have my copy, I have written notes and scribbled all over it. But I happen to have a spare, brand-new copy of the book I will send to one lucky winner - Check out the details on my Instagram, here!