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Sugar – Public Enemy Number 1 – But Is It Really As Bad As They Say?

Tiago Vasconcelos

By Tiago Vasconcelos

Tiago Vasconcelos is a 20 year old competitive powerlifter currently living in Lisbon, Portugal.  He is cofounder of Kratos Strength and Conditioning through which he coaches bodybuildersRead more.

Sugar...  The demon of today's society.  The creator of all illness and the source of all evil.  Sugar makes you fat and unhealthy, right?

I've heard sugar being blamed for almost everything, it's most commonly associated with weight gain, but some people go as far as saying it causes cancer. 

First, what is sugar? Simply, Sugar is a carbohydrate, no more, no less.  What’s more, all carbohydrates are sugar, so sugar is a very broad term. 

In total, there are 3 types of carbohydrates, classified by how long the molecular chain is: monosaccharides, oligosaccharides, and polysaccharides (1)…

  • Monosaccharides are the most basic form, which include glucose (blood sugar), galactose (dairy products) and fructose (found in fruit usually). 
  • Oligosaccharides are known as simple sugar, which are monosaccharides bounded together.  If you combine glucose with galactose, you have lactose, which is found in milk.  If you bond glucose and glucose, you have maltose (found in beer & cereals, etc.)

    And if you merge glucose with fructose, you have sucrose, which is known as table sugar or processed sugar, even though if it's found naturally in honey and cane/beet sugar.
  • Polysaccharides include starch, fibre, and glycogen.

Each “sugar” has a fancy name, but once you associate each type with a food, it's easy to understand. 

Now, let’s analyse some of the common beliefs and arguments used against sugar and whether they are valid or not.  Sometimes I’ll speak about sugar specifically, sometimes about carbs in general, depending on the context.  This is needed because of how board the term sugar is, and that sugar, regardless how you look at it, is always a carbohydrate.

What is a carbohydrate

Sugar and weight gain

Everyone knows sugar makes you fat, that’s common sense – right?  Well, that’s not exactly true.  A caloric surplus makes you fat - no single food or food group makes you fat by magic.  If you have no excess energy then you have no calories to store, and therefore you don't gain fat.

Same with sugar.  There have been studies comparing diets with the same amount of calories and the same macronutrient ratio, only differing in carb sources, and there were no differences in fat loss, regardless of sugar content.  There have also been some studies comparing low-carb (therefore low sugar) versus medium or high-carb diets, in which many cases, the low-carb group wins (2).

Bodybuilder on scales

The media loves to do articles about these, and the headlines of the low-carb diet miracle are quick to show up on your Facebook newsfeed.  However, whenever that happens, the protein intake isn’t matched, skewing the results.  When protein is matched, high carb or low carb doesn’t seem to matter (3).  Protein both preserves muscle-mass and has a better satiation effect compared to carbs (4), easily explaining the difference seen between groups when protein it’s not equated. 

If calories are controlled, sugar isn’t a problem.   But that’s not what usually happens in the real world. 

Some bodybuilders count their calories every day for years on end, but that's the minority, most people don't.  Therefore the effects of it in an ad libitum diet are very important.  The problem with sugar is that it is full of empty calories, there are no nutrients, and it scores very low on the satiety index (5).

This means you're ingesting calories, not really getting very full and are therefore more likely to eat more.  And if you eat enough, you will end up in a caloric surplus and get fatter. 

Sugar also makes food tastier, which can make you prone to eat more.  So although sugar itself doesn't make you fat, it can directly lead you to eat more food, which might make you gain weight.

As a result, people claim that sugar makes you automatically hungry and overeat, so it should be avoided at all costs, but it's not that simple.  Diets must be seen as a whole.  While sugar theoretically doesn't fill you up very much and can make you prone to eating more, it doesn't mean it will happen or it will make a significant difference. 

If 2 people are consuming sugar, one of whom gets 5% of his calories from sugar, and the other 50%, the out-come is obviously going to be different.  This is why context of the diet is needed; you can't just pin-point a single food and say it will ruin your diet and your health. 

If you feel it’s hard to control your intake when your sugar intake is high, simply lower it, but it should be based on the individual, and we shouldn’t make generalisations based on fear mongering.

Sugar is addictive

It’s been claimed that sugar is just as addictive as heroin or cocaine.  This is obviously not true.  No study has successfully proven that sugar, or any other food items are comparable to actual drugs in humans. 

A common argument is that high-sugar foods cause a release of dopamine, which is true, but so do plenty of things, like listening to music, or hitting the gym!  Is it possible for someone to be addicted to sugar? Sure, but that doesn’t mean sugar itself is addictive.

People can be addicted to anything, even water (seriously, look it up)!

Sugar Injection

In 1993, Wilson (6) reviewed the scientific research on binge eating and found the theory that foods cause physical cravings was “without convincing empirical support.”

In a follow up study, Wilson stated:

Review shows evidence for the physiological basis of 'carbohydrate addiction' to be weak compared to drug addictions.  If 'carbohydrate addiction' is a genuine phenomenon then it is probably a habitual dependence based on strong reinforcement, like gambling, rather than a substance-based one.

There has been some interesting research about food addiction in the past years, but it’s still developing, and it’s mostly in the context of obesity or food disorders.  This isn’t very applicable to the general population.   Plus it’s not always about carbs, but food in general or multiplies combination of ingredients (such as sodium, fat, sugar, etc.).

One thing that can be argued for sugar being addictive is that most high-sugar foods are tasty and enjoyable, so you’re more likely to eat to consume more of it and more frequently.  But that’s not a good enough argument to call it addictive.  You also feel good after sex, is sex addictive? Should we avoid it because of it? I’m not convinced.

Sugar and diabetes

I'm seen as an alien every time I speak about this with friends or family, but no, sugar doesn’t cause diabetes.  There are 2 types of diabetes, which have different causes:

  • Type 1 usually develops during childhood, and your pancreas makes little to no insulin.  As a result you need to inject insulin regularly to metabolise glucose, otherwise you die.  We don't fully understand all the causes yet, but it's thought to be mostly genetic.
  • Type 2, however, is caused by a sedentary lifestyle and/or being overweight.  Of course, if someone is 100lbs overweight and sitting on the couch 24/7, it’s likely they’ll be consuming a lot of sugar, but it's not the sugar itself that is causing the problem.

Type 2 diabetes is easily preventable and may even be reversed (7).  It's relatively common for people to stop needing medication when they get in shape after being sedentary and over-weight, which got them diabetic in the first place.

Sugar and blood sugar spikes

When you eat carbohydrates, they are broken down into glucose, which later enters your blood, raising your blood sugar.  It’s a common belief that this is bad, and sugar will cause a massive blood sugar spike, much higher than normal, which would then lead to a massive a crash.

Sugar / glycemic spikes

As we discussed earlier, sugar is sucrose, which is half glucose and half fructose.  What indicates the food's effect on a person's blood glucose levels is the glycaemic index.  In sugar’s case, it has a glycaemic index of around 68 (8), which is not that high.  In fact it’s the same as whole wheat bread, and lower than pineapple, which is 69.

And let's not forget GI values are determined in an overnight-fasted state using isolated foods.  This does not happen in the real world!  When you start adding other foods, it will affect the glycaemic index of the entire meal even further, making it an almost useless concept to begin with. 

The thought that just because a meal contains sugar will cause a massive sugar spike is false.  Regardless, in normal circumstances for healthy and active individuals, elevations in blood sugar shouldn't be a concern anyway as, in my opinion; they're massively blown out of proportion.

Sugar and insulin

When there’s a rise in glucose, the pancreas senses it and releases insulin.  People believe that this makes you store fat and you instantly get fatter.  Well, they’re not wrong.

Insulin indeed allows the glucose to enter your liver, muscle, and fat cells; however insulin only regulates the storage of energy.  It can't magically create or destroy energy.  Even if you have a large spike, your blood glucose and insulin levels will eventually start to come back down.  This cycle happens throughout the day, as seen in the graph below.

Sugar Insulin Graph

If you're eating in a caloric deficit, regardless of the blood sugar spikes from each meal, over a 24h it will all balance out as you will be losing fat during the periods of fasting, and fat oxidation will exceed lipogenesis (fatty acid synthesis).

This means you will burn fat as the net effect, even with blood sugar spikes from each meal.  If insulin was responsible for fat gain than we would expect people who consume more carbohydrates as a percent of their diet to have a higher percentage of body fat than those who consume less, which we don't see, neither in research or anecdotally.

Not to mention protein is also a potent stimulator of insulin, sometimes even higher than carbs (9).  I don’t see anyone worried about the effect their protein will have on insulin release.  Perhaps we should all consume a diet of olive oil and get ripped…

Carbs and insulin sensitivity

In specific cases, such as sedentary and/or over-weight populations, a low-carb diet seems to be superior for health due one’s insulin resistance, which determines how well tissues respond to insulin.

When small amounts of insulin produce a very large response, you have high insulin sensitivity and can handle carb intake better.  But if your body requires a lot of insulin for a similar response, you have low insulin sensitivity a low carb diet may be better.

If someone with low insulin sensitivity was on a high-carb diet, they'd have a much harder time controlling their caloric intake and they'd feel tired and grumpy often.

High carb and low carb foods

However, just like most things related to sugar, this doesn’t have much relevance for active and healthy individuals, since the main factors that determines insulin sensitivity is body-fat percentage and level of physical activity.

Even extremely insulin resistant individuals can eat a relatively high amount of carbs after training, since their insulin sensitivity is temporarily elevated.  It’s true that there's also a genetic component to it, so it's possible for a lean athlete to have poor insulin sensitivity, but such cases are rare, and not the norm.

Regardless of insulin sensitivity, calories are still king and you can still lose weight just fine (10), which will improve insulin sensitivity itself as discussed.  Just be aware that you will have a harder time doing so if you're eating a very high carb diet and your insulin response is poor.  (11)

If with a high carb intake you feel sloppy, bloated, and you experience a crash in energy, simply lower your carbohydrate intake and/or improve your insulin sensitivity by being more active and getting leaner.

This doesn’t make carbohydrates or sugar bad, you simply don’t respond well to a high carb intake.



Some people like to hate on fructose specifically instead of going after sugar in general.  Fructose is a sugar much sweeter than the others, found in fruit and many plants.  Some studies even show fructose can affect your health, but they use extreme and unrealistic amounts of it. 

Like in anything, the dose makes the poison.  You can't simply extrapolate those results to moderate fructose consumption. 

Quoting a review by Salwa Rizkalla in 2013: 

In considering the volume of contemporary literature on fructose, 1 conclusion stands clear: fructose is safe at typical intake levels but can produce adverse metabolic effects when abused—as is true of most nutrients

Another review, which was just published last month [July 2015], concluded:

Higher-level evidence from controlled feeding trials shows that fructose-containing sugars in either liquid or solid form have adverse cardiometabolic effects only when they supplement diets with excess calories compared with the same diets without the excess calories.  

In the absence of harm when fructose-containing sugars are exchanged for other sources of carbohydrate under energy-matched conditions, excess calories appear to be the dominant consideration.

Corn Syrup Fructose table

Many people also like to blame HFCS (high fructose corn syrup) however, the difference between its composition and sugars composition is rather small and your body processes them equally. The only practical difference between sucrose and HFCS is in the bonding.

The glucose and fructose in HFCS is free and unbounded, while glucose and fructose are bonded in sucrose. But it makes no difference, and has similar effects on hunger and satiety.

Added sugar is unnatural

This is a senseless argument to start with!  Just because something is natural, doesn’t mean it’s good, and just because it’s not natural, doesn’t mean it’s bad.

There are “natural” poisonous berries that can kill you, and there are man-made substances that can improve your health and even save your life.  And this is assuming you bypass the problem of defining what is actually natural, which is extremely difficult!

We have been modifying food and the environment as long as we’ve existed, if we get technical, there are very few natural things in our world.  People just like to cherry-pick specific examples to support their bias. 

I’m not saying that processed food (what people usual call “unnatural”) is good and you should have a diet of Twinkies, but what is good or bad should be determined by proper logic and evidence, simply stating something is natural or not doesn’t prove anything. 

Sugar is a recent addition to the human diet

This is often an argument used to people who follow the Paleo diet.  First of all, sugar being a recent addition to the human diet doesn’t prove anything.  Just because our ancestors ate a certain way, doesn’t mean it was the healthiest.

More often than not, we ate what we could to survive based of what we could get from our environment, that’s why diets change so drastically according to geographic location, even in the same time period.  We couldn’t afford to be picky eaters.

Paleo foods

In fact, a study in the American Society for Clinical Nutrition in 2000 (15) estimated that the Palaeolithic diet constituted anywhere from 20 up-to 40% carbohydrates!  Definitely lower than the average diet in today’s society, but doesn’t exactly match the idea that we consumed a low carbohydrate diet.

Most of the diet was made up of fruits (fructose), but sometimes, depending on geography, grains were also included.

In a study from University of Utah (16) 2 years ago [2013], it was shown that that humans and pre-human ancestors have been eating grasses and grass-like plants for about 4 million years.  Similar evidence has been showing up recently.  This is relatively new because archaeological evidence relies heavily on the discovery of hard materials. 

Grains and other soft materials don't survive very long.  But, thanks to today's technology we are now starting to better understand what ancient humans actually ate without relying on tools alone, further expanding our knowledge about the history of human nutrition.

Sugar is the reason we are obese

I already touched on sugar and weight-gain, but some people try to prove it by the fact that there is a correlation between increased sugar consumption and obesity and some diseases


However, research has shown that calorie consumption has increased dramatically over the past few decades (17), and some claim this more than sufficient to explain the increases in obesity (18).  Physical activity decreased (19), further increasing weight gain, and obviously not making us any healthier.

Not to mention, blaming obesity into one single factor is foolish.  Obesity is a very complex topic that has dozens of variables that come into play.  Even though it has an obvious solution - stop eating so much – the factors that lead to that overconsumption of calories are not, and avoiding weight re-gain is a very hard task.

Food exposure, purchasing power, food abundance, cheaper food production, hyper palatable foods are among dozens, if not hundreds of variables that all play a role.  Trying to explain obesity with sugar consumption is a childish and silly way of trying to justify our current health problems.

I asked Dr. Spencer to give his opinion on sugar and obesity:

Sugar has recently been blamed for the obesity epidemic, but it's a little more complicated than meets the eye. 
There may very well be biological plausibility to sugar and obesity among other diseases, but it also depends on what else it is packaged with.  Think about blueberries compared with candy bar. 
We need to stop demonizing isolated single factors and look at the big picture.


Blaming everything we can think of on sugar or carbs is another senseless and unscientific approach to nutrition.  It started with carbs in the 70’s with the Atkins diet.  Then we shifted to blaming fat in the 80’s.  Once we figured that was wrong, we started to go after a specific type of fat - saturated fat.

But damn it, looks like saturated fat in moderation isn't bad either.  Let’s go back to carbohydrates then.  No? Fine, carbohydrates aren't the culprits, but must be the sugar then! Not the sugar? Then processed sugar! Ok not all processed sugar, but HFCS!

Unfortunately, this cycle is unlikely to end, because people refuse to acknowledge that our current health problems are far too complex to blame on a single phenomenon.  It's also hard to admit that we don't exercise as much as we should, or that we simply eat too much.

I consulted Alan Aragon about this topic.  Alan has over 20 years of success in the fitness field, being one of the most influential figures in sports nutrition. His response was:

Alan Aragon

Sugar that's naturally occurring within milk and fruit (also called intrinsic sugars) is really not a concern, especially if there's an awareness of one's total carbohydrate requirement.   Added sugars, such as table sugar, sugar-sweetened beverages, syrups, and sugar added to various desserts and packaged snack foods (also called extrinsic sugars) pose more potential threats to the quality of a diet if they are not properly moderated. 

A call for the elimination of extrinsic sugars is not only extreme, but it's unnecessary.  As the evidence stands, individuals leading a physically active lifestyle and consuming a diet whose macronutrient targets are fulfilled with a majority coming from whole and minimally refined foods can enjoy a minority of their carbohydrates from added sugars and still live ripe, long lives.

Putting an exact number on this limit is difficult, since I don't believe hard lines can be drawn due to the variability of factors that influence the viability of this 'discretionary' allotment. With that said, a maximum of 10% of total calories coming from added sugars seems reasonable as a general guideline.

Competitive and recreational athletes with high volumes of exhaustive, endurance-oriented training may breach this limit and not compromise health or diet quality. As with everything, the individual situation has to be carefully considered; there's no universal prescription.

If there’s something that I want you to take away with this is 2 things:

  • The overall diet and life-style rules above any particular food choice.  Both for body composition and health.
  • Sugar is not the devil.  That doesn’t mean a diet based on sugar is okay (it’s not), nor that reducing sugar intake might not have some benefits for certain populations (such as higher satiation, better diet adherence or higher energy levels)

Context is everything.  As Eric Helms once said, “Good diets can include ‘bad’ foods and bad diets can include ‘good’ foods.”

Tiago Vasconcelos

About Tiago

Tiago Vasconcelos is a 20 year old competitive powerlifter currently living in Lisbon, Portugal.  He is cofounder of Kratos Strength and Conditioning, through which he coaches bodybuilders, powerlifters, and the general public for improvements in body composition and strength improvements.
You can find out more about Tiago via his Facebook page.


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