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Macmillan Childrens Publishing Group

The Fatburn Fix

Boost Energy, End Hunger, and Lose Weight by Using Body Fat for Fuel

Catherine Shanahan, M.D.

Flatiron Books



The Fatburning Advantage: More Energy

Get the Energy You Need to Lose the Fat You Don’t


When your metabolism is damaged, you lack energy.When you lack energy, you want to eat more often, and most of us seek out foods that make metabolic damage worse.It’s a trap—but you can escape if you can get more energy.ENERGY SHAPES YOUR TEMPERAMENT

Are you a morning person, or do you need a few hours to really get going each day? Does a long day at work make you want to head outside for a walk or take a nap? Do you jump out of your seat with excitement when you get an idea about something fun to do, or do you sit quietly in place? Do you find that when you’re really hungry certain people, or certain tasks, irritate you a lot more than they do when you’ve had something to eat?

Believe it or not, your answers to these questions depend less on your personality than they do on the health of your metabolism. So an unhealthy metabolism not only impairs your energy; it also impairs your ability to attain your full human potential.

First, let’s define metabolism: your metabolism provides your body with energy. A healthy metabolism supports pretty much everything your body does, because every physiologic function relies on energy production, everything from learning, memory, and motivation to DNA replication, to cell division, to hormonal function, to the replacement of old worn-out tissue with new growth, to the removal of toxic materials from the body.

A healthy metabolism uses body fat to sustain your energy all day so that you don’t need to rely on food to keep your energy up. When your metabolism is healthy, you have plenty of energy all day long even if you don’t have time to eat. You don’t need to snack when you can burn your body fat. You don’t need beverages to keep you focused. When your metabolism is healthy, your body naturally stays at a healthy weight because your body fat provides you with energy that makes you enjoy staying active.

The important point here is that the job of your metabolism is to ensure all your cells have all the energy they need all the time. When your metabolism is unable to do its job properly, your energy drags. When your energy drags, it affects your moods, your relationships, your interest in exercise, and your ability to function at work. It even impairs your libido, affecting your interest in sex.

Low energy also makes you gain weight. When your energy is down, you’re going to feel lazier than when your energy is up. You’re more likely to choose the elevator over the stairs, and you’re not likely to want to cook a healthy meal from scratch after a long day. All the reduced activity reduces your calorie needs, which makes it all too easy for your portion sizes to exceed the reduced amount of calories you need.

Worse, many people with low energy start using food to keep their energy levels up. They start to use snacks and beverages here and there throughout the day to help sustain their energy. They may need to take snack breaks at work to stay focused on the job. They start to eat slightly larger meals, hoping to prevent the need for snacks. Or they may be so hungry by mealtimes that they eat with their eyes, piling on more than they need or getting second helpings when they know they’ve already had enough. All the extra snacking and mealtime portioning can add up to a lot of calories, which makes you prone to gaining weight. It also makes cutting calorie intake—and thus forcing your reluctant metabolism to burn body fat—feel like physical torture, or at least feel like a lot more work than it should.

Everyone with a weight problem developed their condition due in large part to disruptions in cellular energy supply that slowly but surely over the years cause ever more widespread metabolic damage. What I’m saying is your metabolic damage began before you gained weight, not afterward. It is the reason you gained weight, not just a consequence of the weight gain.

Because metabolic damage is the cause of weight gain, rather than simply a consequence of weight gain, this means that correcting a weight problem is more complicated than instructing you to eat less and exercise more. For one thing, that’s not easy to do while you don’t have the energy you need to make it possible. In order to lose weight, you have to restore your metabolic ability to supply your body’s cells with energy so you can stop needing to snack, stop overportioning at meals, and start to be more active. If your body can produce enough energy, you’ll be less hungry and less tempted by snacks that may be lying around. You’ll be less prone to overfilling your plate. You’ll also be more energized and ready to get up and be active. All those happy consequences of ample cellular energy practically guarantee you’ll lose weight. That’s how a healthy eating program that heals your metabolism (as opposed to causing more metabolic damage) is going to make your weight loss permanent.

So where will that newfound energy come from? When you follow the Fatburn Fix Plan, your energy will come first from foods that sustain your energy and then later, in Phase II, from your ultimate source of supercharged energy: body fat.


Most of the time when we talk about body fat, we’re thinking about weight. But the fact is, we’re actually talking about energy. Body fat is full of energy. And when we talk about fat as energy, suddenly everything changes. We’re not talking about what we look like; we’re talking about how we feel. Do we feel good? Do we feel confident? Do we feel like getting our work done, cleaning the house, going to school, making a difference in the world?

If you woke up energized, in a good mood, and had enough energy all day to check off everything on your need-to-do list, imagine how much that could improve your self-confidence. If you had the mental energy to quickly resolve problems or sidestep arguments or brighten someone’s day with a surprise gift, imagine how much that could improve your entire outlook on life. Our body fat is designed to be the steady source of energy that lasts all day if we need it to, or even longer. Nature designed our bodies to be able to go between meals without energy dips whether the time between meals is two hours or twenty or even more.

In other words, our body fat is supposed to free us up from the need to constantly think about food so we can focus on living life.

But these days, our body fat does not do this. At least not for most of us. And this is the key point of the book, the result of decades of working with patients and researching how foods affect our health. The shocking truth is that modern body fat is very different than what nature intended. The difference I’m talking about is not about how much body fat we have, or where it ends up. I’m talking about the chemical nature of our body fat.

As you read in the introduction, we consume a lot of vegetable oils these days. Most people are not sure what vegetable oils are or where they come from. People often assume vegetable oil comes from junk foods and if they don’t eat junk foods they don’t have to think about it. That’s exactly what those who sell you vegetable oil want you to believe. If you’re health-conscious, then vegetable oil still gets into your body by way of foods that manufacturers work hard to convince you are healthy. A shocking 80 percent of the average American’s fat calories come from vegetable oils, leaving very little room for the healthy fats your cells actually crave. Most of the vegetable oil in your body right now does not come from cooking oils you purposefully added—instead, most of it comes from restaurant meals and packaged foods you’ve eaten.

The fatty acids in these vegetable oils must be stored in your body fat, as your body has no way of eliminating them. Over time, as you continue to eat more and more vegetable oils, the fatty acid composition of your body fat changes. Instead of reflecting the fatty acid profile nature has created to suit our energy needs, the fatty acid composition increasingly reflects the composition of the vegetable oils. Unlike the fatty acids in foods we should be eating, the fatty acids in vegetable oils are difficult for your body to burn in a controlled fashion, and cells can’t extract energy from them with normal efficiency (we’ll go into this in more detail in Part Two later on).

Your body fat is supposed to be your primary cellular fuel. When you can’t burn your body fat for energy, your cells are forced to turn to the less reliable alternative fuel: sugar. In later chapters we are going to discuss the powerful impact of those vegetable-oil-derived fatty acids on energy and metabolism. What I want to do right now is introduce you to the energy challenges faced when your body is forced to rely more heavily on sugar.

Sugar is a less reliable fuel than body fat due to the simple physiologic reality that our body can neither store it in adequate quantities nor transport it through the bloodstream in adequate amounts. For reasons we’ll soon discover, an unreliable fuel supply means your cellular engines will sometimes fail to fire on all cylinders.

Trying to live life while your cellular engines are not firing on all cylinders is going to force you to make compromises. It’s a little like trying to run a fleet of delivery trucks with unreliable engines that constantly stall or slow your vehicles down, delaying deliveries by hours or days at a time. Obviously, your business is not going to thrive the way it would given a fleet of fully operational vehicles. Right now, with blocked fatburn, your body is unable to thrive the way it would given a steady supply of energy.


Aside from the energy advantages of burning body fat, burning body fat makes losing weight much easier. The advantage comes in large part from the simple and undeniable fact that when you want to lose weight, you want to get rid of your excess body fat, which is by definition made of body fat. Not sugar.

Even though this argument may seem obvious, when you visit a typical dietitian or read the typical weight loss literature, all the focus is on sugar. You don’t hear much at all about what to do specifically to burn off your body fat. You’re told to eat fruit, which is loaded with sugar, or whole grains like oatmeal, which your digestive system breaks down into almost nothing but sugar. You’re told to eat frequently, in small amounts, to keep you from feeling hungry, or cranky, by keeping your blood sugar up. You’re also typically told that you need to exercise to lose weight—and here’s where you might think you’ll burn fat. But wherever you go to exercise, the trainers typically tell you that for lifting weights or exercising at high intensity, you need to support muscle glycogen by fueling up with sports beverages or other products that are typically sweetened with sugar.

Let’s talk a moment about where sugar comes from, because even when they don’t specifically mention sugar, when dietitians or anyone else advise eating fruits, pasta, and breads made with flours—including whole grain flours—or starchy foods like potatoes and rice, they’re still telling you to eat foods that will raise your blood sugar. Why do fruits and pasta and so on raise your sugar? Because fruits and starches are loaded with sugar. Your digestive system breaks down fruit to extract the natural sugars. It also breaks down starches from flours, rice, and potatoes into sugar. What about whole grain flour, brown rice, and sweet potatoes? Those all get rapidly broken down into sugar. And not in trivial amounts. An apple, for instance, has more sugar than a Hershey’s chocolate bar; so do two small slices of bread. Even though fruit sugar is totally natural and unrefined, sugar is sugar. And once sugar gets in your bloodstream, it has the same harmful effects whether it came from oatmeal, orange slices, or Oreos. In other words, well-meaning people are unfortunately advising you to eat foods that are likely to raise your blood sugar, which is ultimately harmful to your health.

Burning body fat for fuel not only energizes you in ways that support weight loss; it also gives you a huge collection of tangible health advantages not available to you while your cells are dependent on sugar because burning body fat enables your cells to produce a special kind of brain fuel, called ketones. These advantages were largely unknown until very recently (we’ll learn more about ketones in Part Two).


Many health professionals still believe that if you don’t have any weight to lose, the sort of fuel you’re burning makes zero difference to your health. But burning body fat gives us all kinds of health advantages. Some have to do with ketones, and some have to do with the simple fact that body fat provides you with a steady supply of energy.

Here are five basic but underappreciated facts of physiology that explain why your body will become far more energized as you train your metabolism for burning body fat and lose your dependence on sugar.

1. Our bloodstream can’t carry much sugar at any one time, so sugar burners suffer from frequent energy deficits. At a normal blood sugar level, our bloodstream contains only 4 grams, which translates to about 16 calories. Much more than that damages your tissues because sugar is so sticky that it sticks to all your body tissues, glomming them up. Fat, on the other hand, is not sticky, so it does not glom up your body tissues. If you are a good fatburner, then the amount of cellular energy available in your bloodstream at rest equates to about 60 calories. During exercise, a healthy metabolism can easily dump ten times that amount of calories into your bloodstream. Having more calories in your bloodstream means your body is literally pulsing with energy.

2. We don’t have a lot of space to store sugar in our body, and only the liver can release its stored sugar back into the bloodstream. The average liver stores less than 50 or so grams of sugar as glycogen, and women tend to store even less. 50 grams represents 200 calories. Most people burn about 1 to 2 calories per minute at rest and 2 to 3 during light work activity, so 200 calories will last at most about three hours at a desk job and less than that with employment that requires any kind of activity. Fat stores, on the other hand, are capable of fueling us for days of sustained energy, or weeks at a time at rest and even longer if we’re overweight.

3. If you eat more than a few grams of sugar when your glycogen stores are full, this forces your body to convert the extra into fat. Eating fruit, bread, chips or starchy snacks, and other high-carbohydrate foods multiple times a day forces our hormones into fat-building mode every time. Once we’re in fat-building mode, it’s going to be several hours before we can start releasing body fat from storage again. Eating fat, on the other hand, does not have the same effect on our hormones. Once we’ve burned off or stored any fat from a recent meal, we can get about the business of releasing it back into the bloodstream much more quickly, thus giving our cells a shot at burning it.

4. Foods that raise our blood sugar don’t trigger a sense of fullness. That makes sweets and starches very easy to overeat, and overeating makes us tired. When you eat foods with fat, they make you feel full. So when you avoid blood-sugar-elevating foods, you are less likely to overeat than when you don’t. This is why my patients who can consistently avoid sweet and starchy foods can start being more active and more productive at work even in the early phases of the plan.

5. Sweet-tasting foods intensify your desire for more sweet-tasting foods, creating sugar addiction. Sweet-food addictions, as with all substance addictions, will so powerfully disrupt the mood and reward system in your brain that you start to depend on sweet flavors for your sense of well-being. When your brain depends on sweet tastes and the rush of blood sugar that follows sweet taste for you to feel good, you start to believe that you need sugar to feel good. Rather than creating any kind of desire to be active, say, after work, your brain creates a desire to rest and eat. Once your brain stops convincing you that you need sugar to feel good, you will find yourself more able to get that same good feeling from other life activities, which is essential to helping you enjoy some regular exercise.

Clearly, even though we often equate sugar with energy, the human body is not designed to get energy from sugar. Our bodies are designed for a fat-based energy economy, and that’s why we store extra dietary sugar as body fat.

The last two of the five basic physiologic facts I just introduced are deserving of further discussion, and I will expand on them next. If giving in to your cravings has fostered a negative self-image, what you’re about to learn might wipe away the guilt.


The 60-calorie figure is based on the following: A blood level of free fatty acids of approximately 20 mg/dl, which translates to 1 gram per 5 liters (total blood volume in an average man), or 9 calories—plus a blood level of triglycerides of 110 mg/dl, which translates to 5.5 grams per 5 liters, or about 50 calories; 9 plus 50 is 59, which I rounded up to 60. (Keep in mind that the normal range of triglyceride levels is 70 to 150 mg/dl.) And when we exercise, the amount of fat in our bloodstream can climb ten times higher, which would provide an additional 90 calories for a total of 145.


Sugar was never intended to be a principal fuel source for our body, and the impact of forcing your metabolism to rely more heavily on sugar than nature ever intended is profound. A sugar-based energy economy is bad for all of our organs, but the negative impact on our brain cells is probably the most profound.

You may think poorly of yourself if you know you are likely to give in to temptations like a plate of cupcakes in the office or the extra squirt of caramel syrup in your macchiato. But that’s not really you. Fueling with sugar has turned you into a person who thinks of sugar often and gives in to temptations more often than you’d like. I can tell you from personal experience that is not who you really are.

I used to live for my daily sugar infusion. I’d be writing notes on a patient and thoughts of the chocolate bar I packed with my lunch would pop into my head, intruding on my concentration. I used to run ten miles so I could sit down on my red bean bag chair and finish off a pound of peanut M&M’s. I used to drink coffee with the equivalent of a quarter of a cup of sugar, and when that was gone, my first thought was Only twenty-three hours and ten minutes until I get my next hit. Now that I have transformed my metabolism from sugar dependence to fatburning energy independence, I’m simply not hungry all day and I have zero desire to eat. I am no longer tempted by the batch of cookies in the break room. Now, a perfectly delightful dessert is a few slices of Gruyère cheese melted on dark German rye—it’s seriously every bit as pleasing as cheesecake used to be. But I’m not basing this promise to you on my personal experience alone; the science backs it up.

Your brain controls your food cravings. When your body fat stops serving your brain as an energy source, the brain is pretty smart; it very quickly learns to instruct you to seek out sugar. Your brain also controls your moods and how you will behave at work, at home, driving your car, and everywhere else. This means a sugar-dependent brain can hijack any and all of your habits to serve its need for energy.

Copyright © 2020 by Colorado Preventative Medicine