Three reasons why your body doesn't like too much added sugar

Updated: Apr 5, 2020

Sugar is cast in the role of the dietary villain. It's tempting, delicious and easily accessible, but it's said to sabotage our health. How?

A recent article published in Open Heart, a journal of the British Cardiovascular Society, explains the toll that added sugar can take on our body.

If you don't read on, here's the bottom line. The more sugar we eat, the more difficult it becomes for our body to access energy and use nutrients, even though sugar is energy dense and even if you eat other healthy foods to 'make up' for it.

Sure, there's no doubt that sugar is excellent for a rapid boost. But your body isn't designed to constantly convert the energy from added sugars into fuel. A little here and there is one thing. Daily, repeated doses is quite another.

Added sugar contains nothing but empty calories. It isn't very useful to do any of the things that a food should do to nourish our bodies.

Compare a banana, a chocolate bar and a can of soft drink.

The banana has about 14 grams of natural sugar. The chocolate bar contains about 25 grams + of added sugar. That's just a medium chocolate bar. A regular sized can of soft drink contains about 40 grams of added sugar - that's about 10 teaspoons! The banana also provides fibre and other vitamins and minerals, and needs to be digested. The chocolate bar and the soft drink are nutrient poor, high GI and deliver a sugar shock to the system.

Three reasons that your body doesn't like high dosages of refined sugar

1. Sugar technically provides energy, but on a cellular level it halts the production of energy

Our cells contain mitochondria (little power stations) that generate energy in the cells. To do their job, the mitochondria of the cells require certain nutrients co-factors. Added sugar contains lots of calories, but our bodies can't convert the calories into energy without other nutrients. If added sugar is in plentiful supply, but the required nutrients aren't around, energy production halts.

The problem is not a little added sugar here and there. Your body can probably handle this. It's the consumption of large amounts of added sugar that creates havoc.

Let's use another comparison - chocolate milk and the humble potato.

  • Chocolate milk and potato both contain fuel in the form of carbohydrate.

  • The potato contains vitamins and minerals that contribute to the conversion of the fuel it provides into energy that the body can use.

  • The chocolate milk lacks the accessory nutrients needed to convert its fuel into energy, so the body has to call in outside help.

2. Sugar not only fails to provide any nutrients, it actually displaces other nutritious foods in our diet and depletes nutrients from our body

As a result, too much added sugar starts to deplete our tissue nutrients stores and steal nutrients from other ingested foods to liberate its calories. In excess, added sugar can sap our bodies of the nutrients that other foods provide. The more added sugars you eat, the more nutritionally depleted you can become.

True, a food in its natural form doesn't contain all of the nutrients needed for its metabolism and oxidation. But it will contain at least some of the nutrients needed to liberate its energy. A varied diet should comprise all the nutrients your body needs. To repeat, the problem is not a little added sugar here and there. Your body can probably handle this. It's the consumption of large amounts of added sugar that creates havoc.

3. Too much sugar can mimic 'internal starvation' - our cells can't access energy, and so this triggers hunger signals in the body

Too much added sugar consumption is linked to insulin resistance, which decreases the body's ability to use glucose as energy. The more insulin resistant the body becomes, the more insulin it needs to produce to attempt to clear glucose from the blood. The body can't turn to its other main fuel source - fatty acids from dietary fats and body fat stores - while insulin is present.

It's the perfect storm - glucose is in ready supply, but the body struggles to use it. And as a result, the body struggles to use fat for fuel too, even if the person has thousands of calories stored in body fat tissue. This is what creates the 'internal starvation' conundrum - cells can't generate energy from fatty acids (because insulin is high) or glucose (because the cells become insulin resistant and refuse glucose entry). The authors aptly refer to this as 'starvation in the land of plenty'. This triggers hunger, even though you have only just eaten. Sound familiar?

The conclusion? Added sugar is edible, but it's hardly 'food'

Ultimately, the authors conclude that although added sugar is edible, it doesn't pass as 'food'. The definition of food is 'material that contains essential nutrients, which our bodies assimilate to produce energy, stimulate growth and maintain life'.

It's the perfect storm - glucose is in ready supply, but the body struggles to use it. And as a result, the body struggles to use fat for fuel too.

Added sugar contains nothing but empty calories. It isn't very useful to do any of the things that a food should do to nourish our bodies. But here's the kicker - not only is added sugar a free rider in the body that fails to contribute to our health, it is actively detrimental. In other words, too much added sugar isn't just zero steps ahead, it's a step back.

Why does this matter to me?

First, let's be clear - it's not all or nothing. You don't need to eliminate added sugars. This is unnecessary and probably unrealistic. But foods high in added sugars should not be a daily dietary staple, no matter how fit or active you are.

How much is too much?

Most health authorities recommend consuming no more than 10 % of your daily calories from added sugar - that's 50 grams of sugar (or 12 teaspoons) of a 2000 calorie daily diet. This is intended as an upper limit for the majority of the population, not a suggested amount. In fact, the World Health Organisation updated its Guidelines in 2015 to note that a further reduction to below 5 % (roughly 6 teaspoons) per day would provide additional health benefits.

Be sensible. For me, foods that contain added sugar are a treat, not the norm.

How about 'flexible dieting'?

Flexibility in your diet is important. But it doesn't mean that you can simply select any foods you like so long as they meet your daily macro targets. Some flexible dieters may assure you that it is effective. They may even have hard proof of their results - photos of a lean, sculpted body that they maintain on a diet of sugary cereal and pop tarts. But here's the bottom line. What might 'work' is not the same as what's optimal. Personally, I put too much effort into my training to rely on sub-optimal food for results. 90 % of the time, I will opt for natural, unrefined food sources because this will give my body the nutrients it needs to repair and grow. 10 % of the time, I eat as I like. I find that I do better on a clean diet, because my body likes it and it's more predictable. I don't bloat, I don't have an upset stomach, I don't have food hang overs, I don't have energy crashes. If you are serious about your progress, the last thing you want is to feel crap for your training.

The reality is that if you eat high sugar foods, day in day out, then you put your health at risk. This applies even if you are not fat, or don't have high blood sugar or diabetes. Just because you look thin on the outside, your body might still take a hit on the inside in the long term.

But I'm bulking! I'll shred later, bro.

If you are a bodybuilder, your off season is not an automatic justification for a lengthy, no rules all-you-can-eat diet to 'help you' bulk. A 'dirty bulk' should only be used in a small number of cases as a tool for a purpose - to shock the body into gaining weight and to stimulate muscle growth.

Your body is the only one you have. Show it some respect, and it will deliver the results.

For people who genuinely struggle to put on weight, it might be justified to consume high quantities of high calorie foods that contain added sugar just to bump up calories. This person has already increased their calories from 'clean' foods and added shakes to supplement their diet, but still needs more sheer calories to shock their body into change. Some problem, huh. So, to boost their caloric intake as efficiently as possible, they might opt to include more calorie dense, processed foods in their diet (as most of us know first hand, it is easier to eat a high volume of ice cream and pancakes, than rice and potatoes). This is a deliberate strategy to achieve a specific goal. It accompanies an individualised training program to enable the body to utilise the simple sugars. If the person is smart, they will monitor their progress to ensure that the high calories actually results in the desired weight gain (ie, mainly muscle gain, and a controlled amount of fat gain) and is only used for as long as it remains beneficial (ie, a week, a couple of weeks, a month).

Let your body be your guide. For example:

  • If you put on weight but don't get fat, then it may be that your body is effectively using the glucose from added sugars to replenish glycogen stores and enhance recovery.

  • If you start to get fat, then it might be time to return to predominantly clean foods.

After you max out the benefits, it's not all that useful to continue to consume lots of calories from added sugar if 1) your body can't use them properly for energy to fuel your training, 2) your body struggles to transport the glucose to your muscles to replenish muscle glycogen stores, and 3) in the process, you actually deplete your body of the vitamins and minerals that it needs for hypertrophy.

Take home message

There are not many absolute rules when it comes to diet. But this is one -

No matter who you are, you should monitor and control your added sugar consumption.

If you are a bodybuilder or athlete who relies on processed foods that contain added sugars to put you in a caloric surplus, watch out for the tipping point of diminishing returns.

There's no need to fear sugary foods on occasion, especially if you train hard and often, eat plenty of healthy foods and want to put on muscle. The smart approach is to listen to your body. Your body will tell you if it is happy to put the added calories to good use.

For most people, it's fine to have a 'free' meal every 5 to 7 days that meets your carbohydrate needs from any foods that you like. But most of the time, do you body a favour and keep it clean. Your body is the only one you have. Show it some respect, and it will deliver the results.


James J DiNicolantonio and Amy Berger, 'Added sugars drive nutrient and energy deficit in obesity: a new paradigm', Open Heart 2016: 3.