To understand how all this stuff works, we need to unleash some boring science in the form of a Q&A!
Q: If you’re cutting out all grains, legumes, sugar and dairy, you’re basically eating fewer carbs and replacing it with fat, right? Doesn't eating fat make you fat -- not to mention dangerously prone to cardiovascular disease?
A: Not exactly.
First, some fundamentals.
All food is comprised of three primary macronutrients -- fat, protein and carbohydrates -- that power our bodies with energy in the form of calories. The First Law of Thermodynamics, also known as the principle of energy conservation, says that energy can be transformed, but can't be created or destroyed. You know: Energy in, energy out. In the context of diet, then, the caloric energy in the food we eat can’t just disappear. It has to be stored (as fat) or used (to power, maintain and grow the human body). Calories in, calories out.
Out of this was born the old familiar “Caloric Balance Theory” (a tip of the hat to Adam Kosloff) which maintains that if you ingest more calories than you burn, your body’ll end up storing the remaining calories. In other words, excess calories make us fat. If we eat too much and move too little, we’ll throw our caloric balance out of whack and start putting on some pounds. On the other hand, if we simply eat less and move more, we’ll burn off our existing fat stores and lose weight.
This is the message we've been spoon-fed for decades. And it’s true that if you consistently or drastically overfeed, you’ll get heavier. But that’s not the whole story.
You Aren’t What You Eat
It’s well established that dietary fat -- the fat you eat -- is more calorically dense than protein or carbohydrates. In fact, each gram of fat consumed provides more than twice as many calories as a gram of protein or carbohydrate. Applying the Caloric Balance Theory, people looking to shed body fat have naturally glommed onto the idea that we should avoid eating dietary fat, and choose less calorically dense foods instead.
Plus, for decades, we’ve all heard that excessive fat intake correlates with a host of health problems, from cardiovascular disease to diabetes. Since we all know (or think we know) that these diseases are linked to obesity, many of us conclude that dietary fat must therefore cause obesity. Who cares if correlation doesn’t amount to causation? As the saying goes, “you are what you eat” -- so if you eat dietary fat, your body will turn into fat, right?
If the key to weight loss and overall wellness is to take in fewer calories, and if dietary fat makes us fat and sick, the solution, it would seem, is to go low-fat -- right?
Sounds reasonable. And over the past few decades, it’s become the common refrain among the vast majority of doctors, food companies, health authorities and nutrition experts. Dissenters are dismissed as conspiracy theorists, fringe scientists and bacon-obsessed Atkins groupies whose glucose-deprived brains have misfired. As a consequence, the low-fat movement has not only persisted, but has been widely and blindly accepted as fundamentally true -- despite mounting evidence to the contrary.
It's not dietary fat that's making us fat. It's the overconsumption of sugar.
- When eaten, neither protein nor fat -- without carbohydrates -- has any effect on blood glucose. But when we take in carbohydrates, our blood sugar levels shoot up. (This isn’t news; in fact, it’s the scientific basis underpinning the popular movement away from eating refined carbs like white bread, which have the effect of suddenly spiking blood glucose. But as we’ll discuss later, whole grains aren’t the bees’ knees, either.)
- Whenever blood glucose levels rise, the pancreas reacts by releasing a surge of insulin into the bloodstream. Insulin is a hormone that happens to be the primary mover and shaker in human metabolism. Among its many functions, insulin manages nutrient storage by driving excess blood sugar, fats and protein into the interior of our cells, where they can be used as energy or stored as fat.
- Although there are numerous factors that can affect how much insulin we produce, as well as how our bodies respond to insulin and blood sugar, the basic rule is this: The more carbohydrates we eat, the more insulin we end up secreting in reaction to the spike in blood sugar.
- As a result, two key things happen:
- First, with all the excess blood sugar and surge in insulin, the liver no longer stores glucose as glycogen -- a fuel source for the body. Instead, the glucose is synthesized into fatty acids, which are exported from the liver as lipoproteins. These lipoproteins are ripped apart as they circulate through the body, providing free fatty acids to be sucked up into the body’s cells -- including the body’s adipose fat cells, in which the fatty acids are then “bound up” together to form triglycerides.
- Insulin also inhibits the breakdown of fat in adipose tissue by interfering with the mechanisms that enable triglycerides to split into their constituent fatty acids. Triglycerides are bigger than fatty acids -- and too big to escape our adipose fat cells. In other words, once triglycerides form in your adipose fat cells, the excess insulin produced by your body makes it difficult for you to break them back down. So when we eat more carbohydrates and produce more insulin, more triglycerides -- which are also now prevented from breaking down into fatty acids -- are synthesized and locked up inside our fat cells.
- And so, over time, our fat tissue swells.
If my technobabble doesn’t make make sense, take a look at this video:
But wait – there’s more! An excess of insulin in our blood isn’t just bad because gives you an unsightly muffin-top. It’s bad because it can make you very, very sick.
Let’s say you’re a carb junkie. You stock up on bread, pasta, rice and 100-calorie packs of Snackwells because they’re low-fat. They know you by name at Jamba Juice and Auntie Anne’s Pretzels. The constant bombardment of sugar in your bloodstream -- and the excess insulin released to move the sugar out of your blood -- eventually blunts your insulin receptors to the effects of the insulin. (Your insulin sensitivity is down-regulated -- kind of like what happens when you linger in a busy kitchen for more than a few minutes: Soon, the cooking smells seem to fade.)
The likely result? Insulin resistance -- a.k.a. pre-diabetes -- meaning your insulin receptors are no longer efficiently activated by the constant rush of insulin that’s secreted to deal with the sugar in your bloodstream. Your insulin receptors lose their ability to effectively move the sugar out of your blood, so when you eat carbs, your blood sugar level stays high -- which, in turn, triggers your pancreas to pump out more and more insulin until there’s finally enough to get your sluggish insulin receptors to do what they’re supposed to do: lower your blood glucose level.
But now, you have a crapload of excess insulin floating around in your system. Bad news. This condition, also known as hyperinsulinemia, leads directly to Metabolic Syndrome (a.k.a., Syndrome X): a cluster of disorders including coronary disease, Type II diabetes, hypertension and obesity. Not fun.
Again, I'm no scientist. I'm just another idiot with a library card and a big mouth, so you have no reason to put any faith in what I've just written above.
But if you're at all interested in the science of fat metabolism, I urge you to read "Good Calories, Bad Calories," which lays out a much more compelling case than I ever could. For those who can’t stand the thought of sifting through the science-y stuff, Taubes recently penned an easier-to-read volume entitled “Why We Get Fat: And What To Do About It.” And for those of you who can’t be bothered to read a book of any length at all, skim these notes or read this summary of "Good Calories, Bad Calories."
(Although I'm kind of bashing carbs here, note that Paleo eating isn't necessarily low-carb. But because grains, legumes and sugar are verboten, Paleo enthusiasts tend to take in fewer carbohydrates than most people. Another way of thinking about this: The Paleo crowd isn’t “low-carb”; it’s everyone eating the Standard American Diet who are eating high-carb.)
Q: But isn’t weight control all about willpower and following the "calories in, calories out" rule?
A: Not exactly. Calories aren't all created equal.
Take another look at the First Law of Thermodynamics. The Caloric Balance Theory suggests that an imbalance between caloric intake and energy expenditure drives changes in weight. But that’s not necessarily the case. Under the First Law of Thermodynamics, it’s equally possible that the reverse of the equation is true: a change in weight causes caloric imbalance.
As Taubes puts it:
[S]ome regulatory phenomenon could drive us to gain weight, which would in turn cause a positive [or negative] energy balance -- and thus overeating and/or sedentary behavior. Either way, the calories in will equal the calories out, as they must, but what is cause in one case is effect in the other... This simple misconception has led to a century of misguided obesity research.But under Taubes’ theory, what type of “regulatory phenomenon” is driving the development of beer bellies, saddlebags and big asses?
Taubes’ answer: The lipophilic -- a.k.a., fat-loving -- properties of our bodies’ adipose fat tissue. Simply put, by eating massive amounts of carbs, we seriously screw up our insulin levels, and therefore, our metabolism. Excess insulin causes our adipose tissue to swell, and we get fat. And -- consistent with the First Law of Themodynamics -- this change in weight causes a caloric imbalance, which triggers hunger. So we eat more. (To learn more about this “lipophilia theory” without having to go to the bookstore, check this out.)
Don’t get me wrong: I’m not saying that the First Law of Thermodynamics works only in this one direction, and that it’s always a change in body weight that drives a change in caloric consumption. I’m suggesting that the First Law of Thermodynamics is a two-way street; while changing our caloric intake can certainly affect our weight, changing our weight can also affect our caloric intake.
Q: So calories still count?
A: Yes. Kind of.
Face it: If you go hog-wild and ingest tons of excess calories a day, you're bound to gain weight. And on the other end of the spectrum, caloric restriction will spur weight loss. Even if you're subsisting on Twinkies.
But when it comes to weight management, strict calorie-counting is kind of pointless because your body’s metabolism (assuming it’s not been thrown out-of-whack) has a way of maintaining its natural set-point. Homeostasis is a wonderful thing.
All calories are not created equal. Given what we know about the insulin-driving properties of dietary carbohydrates, sucking down a Neverending Pasta Bowl at the Olive Garden is likely to make you fatter than having a steak -- even if you're taking in the same number of calories. Weight loss just isn't as simplistic or one-sided as advocates of the Caloric Balance Theory would have you believe.
If you take two people of the same weight -- one on a high-carb diet and one on a low-carb diet, but both eating the same number of calories -- both will shed pounds if there’s a caloric deficit. That’s just the nature of the First Law of Thermodynamics.
But the carb fiend is going to be releasing more insulin than the low-carb eater, and that excess insulin’s going to interfere with the breakdown of triglycerides in fat cells. Recall that not only does insulin store fat in adipose fat cells, it also prevents the fat that is already in a fat cell from breaking up into fatty acids and exiting the cell. So all else being equal, the high-carb eater’s going to hold on to more fat than the low-carb eater.
Also, not to get too science-geeky or anything, but we should touch briefly on lectins and leptins. There's evidence that foods high in lectins (like cereal grains and legumes) trigger leptin resistance. Leptins are hormones that tell you when you're full, so when you're leptin resistant, you tend to keep on eating. Conclusion: When you eat a crapload of carbs, the result is that you have a much more difficult time reaching satiety, and you end up eating even more.
Q: You're telling me that eating carbs make you want to eat more?
A: Yes. Specifically, carbs make you want to eat more carbs.
In addition to what I described above, you should know that grains are addictive. Here’s a paragraph from “The Origins of Agriculture – A Biological Perspective and a New Hypothesis” by Greg Wadley and Angus Martin:
The ingestion of cereals and milk, in normal modern dietary amounts by normal humans, activates reward centers in the brain. Foods that were common in the diet before agriculture (fruits and so on) do not have this pharmacological property. The effects of exorphins are qualitatively the same as those produced by other opioid and/or dopaminergic drugs, that is, reward, motivation, reduction of anxiety, a sense of well being, and perhaps even addiction. Though the effects of a typical meal are quantitatively less than those of doses of those drugs, most modern humans experience them several times a day, every day of their adult lives.Now you know why folks are addicted to cookies and cupcakes, but not eggs and ribs. Take away their carbs, and the junkies go into withdrawal.
But wait -- there's more! Serious dieters tend to exercise. A lot. Exercise -- especially chronic cardio -- makes people want to eat more. Really. And exercise makes 'em hungry for carbs in particular. Plus, low-fat dieters are apt to ditch fat and protein in favor of more carbs because they’ve been told that this is better and healthier for them. But as I've pointed out , eating carbs actually makes folks want to eat even more -- and specifically, more carbs. What comes next? Caloric excess. Plus, the carbs they eat will drive fat into their fat cells, where they’ll stay trapped.
Let's face it: We all know people who constantly diet and exercise like crazy, but never seem to lose much weight. (Don't tell me you've never seen a less-than-svelte aerobics instructor or a plus-sized jogger with ham-hock shoulders and thighs.) Could it be because they’re starving from all the incessant cardio they're doing, and then snarfing up carbs because they mistakenly think they've "earned" an extra cupcake?
Even if they restrict themselves low-fat and fat-free foods, a lot of folks can't seem to shed the pounds. Is it because they're eating lots of pasta and bread, thinking that these "low-fat" foods will somehow prompt weight loss?
I think we can all agree that starvation diets -- the kinds featured on TV shows like "The Biggest Loser" and "Oprah" -- are not sustainable. A body can't run at a calorie deficit forever. Is it any wonder calorie-restriction diets are also known as yo-yo diets?
Q: So if you’re so anti-carbs, why don’t you just follow the Atkins Diet?
A: First of all, I’m not anti-carbs as a blanket matter. Demonizing carbs doesn’t make a lot of sense -- especially given that people like the Kitavans of Papua New Guinea are healthy and thriving despite subsisting on a high-carb diet. The role of excess carbohydrate intake in the development of insulin resistance, obesity and metabolic diseases is just one piece of the puzzle. We also have to consider the role of pro-inflammatory agents in certain foods, the leptin content in grains and legumes (discussed above), and each individual person’s need for glycogen repletion (for example, after strenuous activity).
While many Paleo eaters skew towards the low-carb side (especially those who are still in the process of losing body fat and reversing their metabolic problems), there are plenty of others -- myself included – who actually eat a good amount of carbs on a regular basis. I consume lots of vegetables and a moderate amount of fruit. Plus, after every workout, I wolf down a big ass sweet potato with some protein. I’m clearly not going out of my way to go low-carb. But by avoiding processed foods (which are chock-full of sugar, grains and/or legumes), I’m still consuming far less in the way of carbohydrates than most people.
For more information about all this stuff, go visit my primer on the Paleo diet.
