Quick Summary tl;dr
Sugar causes the liver to make fat and sends a hormonal signal to make fat cells grow.
Being a normal weight does not alone mean your body can handle sugar well.
If you know you are insulin sensitive and metabolically healthy, moderate sugar from natural sources may be safe to support high-intensity activity.
Sugar is an addictive substance. It works on the same brain systems as drugs of abuse.
Restricting sugar can be liberating!
Non-nutritive sweeteners can be a crutch for some people.
You can’t eat in moderation or intuitively until you address any underlying sugar and processed food addictive tendencies.
In answering the question, “Are sugar and sweet harmful?” First, we have to define the subject and object of the question.
The subject. What is sugar? For the purposes of this article, I’m defining sugar as any edible substance that meaningfully spikes blood sugar. This includes but is not limited to added sugar and syrups, tropical and high-glycemic index fruits, and products containing refined grains.
The object. Harmful to who? Because 42.4% of Americans are obese, 70% are overweight or obese, and 88% of Americans are metabolically unhealthy (and one-third of Americans are projected to have diabetes by mid-century) ( Araújo et al, 2019), I think it’s most relevant to address the 88% majority first.
What Does Sugar Do in the Body?
If you are metabolically unhealthy — in the 88% — then dietary sugars are certainly not benign. Here is a list of just some things that sugar does in the body.
Sugar Spikes Insulin
Sugar spikes insulin levels, which sends a hormonal signal to your fat cells to grow.
Sugar is Turned into Fat
At the same time, in your liver, sugar is turned into fat via a process called ‘de novo lipogenesis.’ In fact, your body is so good at creating fat from carbs and sugar that trading calories from carbs and sugar for those from fat actually decreases the fat in your bloodstream, triglycerides!
Fructose, Cortisol and Visceral Fat
Fructose, which is found as part of normal cane sugar, high-fructose corn syrup, and in honey and sweet fruit, is particularly good as being turned into fat. Excess fructose also sensitizes fat cells to the stress hormone, cortisol.
Because different fat cell types respond differently to cortisol, this leads to a shift from storing fat in its relatively healthy subcutaneous form to storing fat in inflammatory visceral fat — the worst form of fat.
Fructose is particularly good as being turned into fat. Excess fructose also sensitizes fat cells to the stress hormone cortisol leading to more inflammatory visceral fat.
Insulin Resistant People Have High Sugars and Fats in the Blood
Because a metabolically unhealthy body is an insulin resistant body, the insulin released by your pancreas, which is supposed to stop the liver from making more sugar itself through gluconeogenesis, can’t do so.
As a result, the liver can continue to make sugar. But because of an unfortunate quirk in metabolism, insulin still tells the liver to make fat. ( Li et al, 2009) This means that eating sugar doesn’t stop the liver from making sugar, but it also causes the liver to make fat, leading to high sugars and fats in the blood.
Insulin Resistant Muscles Can't Take Up Blood Sugar
Your muscle cells, being insulin resistant, are also not good at taking up blood sugar. Muscles are supposed to be the main sink for blood sugar.
So, now, you have a situation where sugar has increased insulin levels. Your fat cells are being told to grow while the liver is making more fat and dumping fat and sugar into the blood. The muscles can’t take up the sugar as well, exacerbating the problem further.
Insulin Resistant People Burn Fewer Calories
When your muscles are insulin resistant, it also means you’ll burn fewer calories after eating — the so-called ‘thermic effect of food.’ ( Habtemichael et al, 2021) Correspondingly, that higher carb, higher sugar diets decreases total energy expenditure.
Sugar Turns LDL Cholesterol into "Bad" Cholesterol
Sugar also binds to, or “glycates,” molecules in your blood such as LDL cholesterol particles. LDL cholesterol is typically thought of as “bad cholesterol,” but there is more to the story. LDL is born big fluffy and healthy but can age and shrink to become small and harmful.
Sugar promotes the conversion of healthy LDL to unhealthy small dense LDL by binding to LDL and preventing it from getting taken up into the liver. ( Ikezaki et al, 2021) At the same time, sugar damages blood vessel walls, leading to a scenario where you have small unhealthy LDL trapped in the blood with nowhere to go but into a damaged artery wall.
That’s why it’s no surprise that insulin resistance is a 4.5-fold stronger risk factor for heart disease than is high total LDL. (Dugani et al, 2021)
Insulin resistance is a 4.5-fold stronger risk factor for heart disease than is high total LDL.
Sugar is Bad for Brain Health
In addition to fat cells, the liver, muscles, and the heart, the brain is vulnerable to sugar. Sugar and insulin resistance "conspire" (if you don’t mind a little anthropomorphization) to promote the aggregation of proteins associated with cognitive decline, decrease the efficiency with which regions of the brain work together, starve the brain of energy, and ultimately promote a cascade of events that precipitates conditions like Alzheimer’s disease. ( Mujica-Parodi et al, 2020, Norwitz et al, 2019)
Sugar Can Cause Hormone Triggered Cravings
Sugary foods lead to dramatic hormonal fluctuations that send more blood to the reward and desire center of the brain, and trick the brain into craving more sugar. ( Holsen et al, 2021, Lennerz et al, 2013) Thus, eating sugary foods can quickly start a vicious cycle of sugar, craving, and overeating.
The list goes on... Sugar is the gateway drug to poor glycemic control and insulin resistance, which have a role in almost all non-infectious diseases. If you want to learn more, I strongly recommend this lecture by Dr. Ben Bikman, an expert on insulin resistance.
Sugar is an addictive substance. It works on the same brain systems as drugs of abuse.
Is Sugar Okay if You Are Thin and Balance Caloric Intake and Output?
Let’s get a myth out of the way. Just because you’re skinny does not mean that you’re healthy. In the United States alone, there are three-million people with diabetes who are normal weight, and tens of millions more are insulin resistant and normal weight. Your weight and BMI do not tell you whether your body can handle sugar.
And here is another myth, balancing your caloric intake and output will lead to the health and body composition goals that you desire.
Cushing’s disease, a condition in which the body creates too much stress hormone, is an obvious example. In Cushing’s disease, hormonal changes cause the body to direct energy away from muscle towards unhealthy stores of fat. Patients develop a protruding gut and fatty back, while at the same time their musculature and limbs shrink. They can be a normal weight, but not the kind of normal weight anyone would want.
Cushing’s disease is an extreme example, but it’s just one example on a spectrum. Having insulin resistance can also cause your body to misdirect fuel to where you don’t want it. As put nicely by the authors of a recent study in Nature, insulin resistance in the brain can “result in altered substrate distribution with preferential energy accumulation in unfavorable fat depot." ( Kullmann et al, 2020) In simple terms, having insulin resistance — most people do, to some extent — causes you to put calories in unhealthy fat rather than muscle.
It’s not about the calories, it’s about how your body handles the calories. And, overtime, sugar can nudge the body in a direction of insulin resistance, more fat, less muscle, and overall poor metabolic health — even if you are a normal weight and balance your caloric input and output.
It’s not about the calories, it’s about how your body handles the calories.
Is Sugar Okay if You Are Insulin Sensitive and Active?
But what about if you are a healthy weight and you’re genuinely insulin sensitive and metabolically healthy — part of the 12%. If you’re part of this population, then your body can probably handle sugary food just fine, especially if you’re using that sugar to fuel sport.
For example, I was a runner in high-school and college. Some days, I’d run twenty miles and then go to the gym to lift heavy weights. During this time, I certainly did not shy from whole food carbohydrates and they were probably important in supporting optimal performance. But sugar?
I’d argue that we don’t have sufficient data to fully answer the question of whether eating sugar “in moderation” as a fuel is harmful to an insulin sensitive highly active person, if that person is otherwise consuming a nutrient rich diet and if that behavior is continued over decades.
I could argue the answer either way, but for the time being I’d personally only be comfortable including sugar in a diet if…
- You know that you are insulin sensitive because you’ve had a Kraft test, two-hour insulin, HOMA-IR, or even fasting insulin,
- and you are responsibly tacking the trajectory of one of these tests overtime.
- and you are otherwise eating a diet filled with sufficient nutrients.
- and you’re active.
How many people meet these criteria?
Sugar “In Moderation” is a Trap
“In moderation” is an important phrase to unpack. What does it mean, and is having some sugar “in moderation” okay?
First, imagine it’s your birthday and you want birthday cake. Fair enough. Birthdays only come once per year and a few slices of cake on an annual basis certainly won’t harm your long-term health. Go for it. Oh, but you certainly also have to make an exception for Thanksgiving. Those candied yams are too good. Christmas too. Let’s just make it the whole holiday season. Then there are other people’s birthdays, other holidays, and so on., It’s a slippery slope.
That said, for those who can truly achieve maintaining metabolic health by eating anything “in moderation,” I am in awe of you. For most people, I think this is almost impossible because of the food environment in which we live as well as the addictive properties of sugary foods.
To illustrate that point, let me ask you a question: Why do you think that the processed food and sugar industry, including companies like Coca-Cola, PepsiCo, Kellogg’s, and General Mills have historically funded the Academy of Nutrition and Dietetics, the body that determines what dietitians learn and advise?
No dietitian will tell a patient, “here, have a coke.” So why would the sugar industry waste its money? What are they buying? The answer became clear to me when reading the book, “The Dietitians Dilemma,” by dietitian Michelle Hurn. Therein, she describes how companies like General Mills use their influence to determine the learning objectives for dietitians’ continuing education, including teaching patients, quote, “the role of packaged foods play in a sustainable diet.”
In a nutshell, the food industry pushes the agenda of anything “in moderation.” Packaged foods are okay, in moderation. Coke is okay, in moderation. The free daily Krispy Kreme you can now get for getting your COVID19 vaccine is okay, in moderation. It actually sounds quite reasonable on the surface. Treating yourself now and then sounds like it should promote sustainable diet. But there’s a catch that can be summed up in a simple formula.
“In moderation” + “addictive sugary processed foods” = ???
If you can’t figure out what ??? is, we will fill in the blank together in a bit.
Sugar Can be Addictive
Sugar is an addictive substance. ( Avena et al, 2007) The brain systems that support the abuse of addictive drugs, like nicotine, amphetamine, or cocaine, are the same systems that support sugar addiction. These include the dopamine system and opioid system and other components of the limbic system, which controls emotion.
Just like drugs of abuse, the more sugar you have the more sugar you want. This is called sensitization. Interestingly, in studies performed on rats, sugar cross-sensitizes with amphetamine or cocaine. In other words, giving rats sugar sensitizes them to these drugs of abuse. Why? Because they work on the exact same brain systems.
In fact, the neurobiological and neurochemical imprint of drugs of abuse and sugar are highly similar. They decrease the expression of certain dopamine receptors, like the D2 receptor, as well as decrease the expression of brain opioids, like enkephalin.
Also similar to drugs of abuse, sugar restricting can cause temporary withdrawal symptoms. And these symptoms can be mimicked in the presence of sugar by injected opioid blockers, further confirming that sugar and drugs of abuse work on the same systems.
We live in a sugar-laden world in which many of us need more sugar drug to get the same “hit.” So, let’s fill in the question marks together.
"In moderation” + “addictive sugary processed foods” = 42.4% obesity.
That’s where we are right now and that is what the processed food and sugary industries are buying by funding dietitians’ education and scientific research. If you want a dietitian’s word for it, read Michelle’s book.
Admittedly, one could make the order of magnitude argument i.e that sugar and opioids might work on the same system, but the latter is stronger. But this argument falls flat when you consider the social and environmental contributions to addiction.
To abuse a substance, the motivation to use the substance needs to outweigh the deterrent of social stigma as well as the obstacles in the way to obtaining the substance. Drugs like heroin and cocaine need to pack a bigger punch to be addictive. By contrast, sugar “in moderation” is socially encouraged and everywhere. It doesn’t need to pack as big a punch to be addictive.
In closing on the topic of sugar addiction, I have just one more rhetorical question to set up the next section: Would you tell an alcoholic that it’s okay to have alcohol “in moderation?”
Sugar is a substance of abuse that's hard to avoid. Not only does it have addictive properties, but it is socially encouraged and everywhere. No wonder sugar "in moderation" is so hard.
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If You Eliminate Sugar, Are You “Restricting?”
The attack dog of “in moderation” mentality is the accusation that “restrictive diets” are not sustainable.
That’s true, but only to a limited extent. For example, if you try to restrict calories without changing anything else, you’ll fail in the long term. You can be the most motivated person in the world, but conscious caloric restriction leads to a slowed metabolism, obesogenic changes in the microbiome, cravings and mood disturbances. Biggest Loser reunions don’t happen for a reason.
But “restricting” sugar is fundamentally different because you’re not fighting your biology but working with it! Most of us are chained to sugar like a ball and chain. It hacks the brain and we feel compelled to treat ourselves “in moderation” every single day, if not multiple times per day. But, when you eliminate sugar and carbohydrates, your body progressively learns to use fat as fuel and those cravings do dissipate. The chain is broken, and you are liberated.
Here is a list of quotes from clients with whom I’ve worked who reversed diabetes, pre-diabetes, or obesity by restricting sugar. Not one has regressed on her/his goal.
“I can’t believe the cravings are gone. I feel so free!”
“I thought I needed my sweets. I thought life would be miserable without them, but I don’t miss them at all. And I’ve lost 42 pounds!”
“Just got offered birthday cake at the office. I politely declined without effort. I actually didn’t even want it whereas before I would have needed to exert serious willpower to say no.”
“Nick! After six months without sweets I just treated myself to a handful of wild blueberries and it was literally the sweetest thing I’ve ever tasted. Ice cream never tasted so good!”
This last quote, about the blueberries, may be the most telling. By restricting sugar, you reboot your appetite and taste systems, returning to a metabolic state that is most compatible with human thriving.
What that person was experiencing was not an exaggerated reaction to a handful of blueberries, but a normal reaction. That’s what a small amount of low-sugar wild berries should taste like and it’s the rest of us who are robbed that sweet pleasure by, ironically, sugar.
I realize that sounds like a paradox, so I’ll try to reframe it.
We think the pleasure we derive from food is associated with intrinsic properties of that food. The ice cream sundae must be more of a treat than a few berries. But we’re wrong. The pleasure we derive from food, including sweet taste, arises from an interaction between compounds in the food and our biology.
The “sweet” is in the mind, not in the quantity of sugar. I could give you my first-hand account and many secondhand accounts, but the only way to really understand what I mean is to try it yourself. And, for those of you reading this who know what I mean, please share your experience in the comments.
But if nothing else from this piece sticks with you, remember this: Restricting sugar is liberating.
Restricting sugar is liberating! You can’t eat in moderation or intuitively until you address any underlying sugar and processed food addictive tendencies.
Are Artificial Sweeteners Okay?
Non-nutritive sweeteners, including both natural sweeteners (think Stevia) and artificial sweeteners (think aspartame), have their pros and cons. The obvious pro, for most people, is that they are basically calorie free. However, that doesn’t necessarily translate into weight loss.
For example, a Cochrane review on the intake of non-nutritive sweeteners found “No evidence of any effect on overweight or obese adults or children actively trying to lose weight.” They also reported that researchers found significantly higher increase in blood glucose in children of preschool age receiving aspartame and saccharine compared with normal sugar. Not all the studies reported negative results, but the fact that many do suggests that just giving the body sweet without the calories does not fix the problem.
Returning to the “in moderation” concept, here’s something else to ponder. Research funded (Veldhuizen et al, 2017), in part, by Coca-Cola discovered that drinks with 112.5 Calories (and artificial sweetener) were preferred over those with 150 Calories. Why? The answer is immensely complicated but boils down to the fact, again, that pleasure is in perception. The body’s hormonal system and brain perform careful calculus to adjust taste preferences, and the sugar industry pours billions of dollars into figuring out how to use that biological calculus to make us always want more.
Artificial sweeteners are a lever the food industry uses to get us to eat more of their products without the guilt but often with just as much of a negative metabolic impact. I suppose ignorance is bliss, and bliss and diabetes.
Furthermore, artificial sweeteners, like aspartame or saccharine, can screw up the microbiome. ( Suez et al, 2014) For example, feeding saccharine to people who didn’t usually eat artificial sweeteners caused most to become glucose intolerant within one week. And, when their microbiomes were transplanted into mice, those mice also became glucose intolerant, proving that saccharine messed up the microbiome to cause glucose intolerance.
But it’s not all doom and gloom. There are certain natural non-nutritive sweeteners, like allulose, stevia, and monkfruit, along with the sugar alcohol erythritol, which have a superior profile. To the best of my knowledge, there isn’t evidence that any of these four options meaningfully spike blood sugar or insulin. And they are likely safer for the microbiome.
Therefore, allulose, stevia, monkfruit, and erythritol may serve as useful crutches for those wanting to cut sugar but not sweet. Do I personally recommend this? No. In my experience, restricting sugar and sweet together is the best way to let people’s metabolism and taste perceptions recalibrate so they become liberated from the shackles of sweet.
Wouldn’t it be nice to experience blueberries as more indulgent than ice cream?
Intuitive Eating, the Holy Grail!
I think a good place to end would be on the concept of “intuitive eating,” which is related to the concept of “in moderation.” Some argue that it’s best to listen to the body. It’s wise and it will tell you what it needs.
But instructing someone to eat “in moderation” and “eat intuitively” is like telling a driver direction for how to get to point X by saying, “And then you arrive at point X.” Technically, it’s accurate. Practically, it’s useless.
Eating intuitively is the goal, but to get there you need proper directions. Step 1 is reducing or eliminating sugar. This helps restore metabolic health and liberates you from the shackles of sugar. If you think those shackles are unbreakable, I promise you, they are not.
Again, if you remember nothing else, remember this: Restricting sugar is liberating.
Eating intuitively is the goal, but to get there you need proper directions. Step 1 is reducing or eliminating sugar.
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