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How do Diet Sodas affect our health?

How do Diet Coke and other low-calorie drinks affect our health and weight?

We usually choose low-calorie diet drinks as a healthier alternative to sugary drinks such as colas and other lemonades, packet juices, etc.

We consider diet drinks to be healthier because they have few or no calories. In other words, the main difference between, for example, Coke and Diet Coke is that sugar is replaced by artificial sweeteners and by switching from regular Coke to Diet Coke, we can significantly reduce our sugar/calorie intake (100 g of regular Coke contains almost 10 g sugar/42 kcal).


At the same time, many studies suggest that this choice does not actually help you lose weight. Even worse, low-calorie diet drinks may even contribute to weight gain!

I looked into the matter, and the findings were really surprising. That’s what this article is about.


Before we begin, I would like to touch briefly on two points:

  • What does “Diet” mean? Specifically, which food or drink is diet and which is not?
  • The role of research in proving or disproving various hypotheses. Or, more precisely, what are the types of studies, and what do they prove or do not prove?

Types of diets

Today, we mostly understand the word “diet” as a diet plan for weight loss.


It has a much broader meaning – in fact, the word “Diet” refers to everything we put in our mouths daily.

Many want to lose weight and have products in their fridge that help them achieve this goal.


Goals can vary from person to person, for example, to reduce the symptoms of a disease, to comply with religious dietary restrictions, to increase body mass, etc.


The contents of their pantries and fridges will change accordingly – different diets will be followed.

Here are just a few examples of how different diets can be:

  • Cultural and regional diets, which reflect the traditional eating habits of different cultures, such as Mediterranean, French, Japanese or Indian cuisines (or diets), etc.
  • Diets targeting specific nutrients or ingredients, such as low-sodium diets, high-fibre diets or diets aimed at improving calcium intake.
  • Therapeutic diets, such as the DASH diet for hypertension, the Mediterranean diet for heart health or the ketogenic diet for epilepsy.
  • Diets that exclude specific allergens, such as the gluten-free diet for coeliac disease or the dairy-free diet for lactose intolerance.
  • Dietary restrictions linked to religious or spiritual beliefs, such as kosher or halal
  • Diets aimed at reducing the effects of food production on the environment, such as vegetarian and vegan diets.
  • Diets followed for aesthetic purposes or to improve body composition, such as diets to increase muscle mass or diets to improve the health of skin, hair, etc;
  • Diets to increase life expectancy, such as the Okinawa diet.
  • Diets to improve healthy gut microflora, such as diets that include probiotics and prebiotics.
  • Diets are used to treat eating disorders such as anorexia or bulimia.
  • Diets to enhance athletic performance, such as diets for endurance sports or strength training.
  • General dietary guidelines focus on a balanced intake of all essential nutrients to promote general health and well-being.

As you can see, the range is quite wide 😊.


The use of the word “Diet” is also ambiguous:

  • In the scientific community, it refers to products that, based on nutritional science, can contribute to a person’s health and/or well-being.

On the other hand.

  • In marketing and advertising, it refers to products that the manufacturers believe contribute to weight loss (either through appetite suppression or reduced calories).

How many studies are needed to support a nutrition claim?

To illustrate the point, let me ask the question: ‘Is wine bad for your health?’.

There is indeed a lot of research on this topic. A large proportion of them warn us of an increased risk of cancer, and we all know that wine should not be consumed before getting behind the wheel of a car because alcohol slows down our reaction.


We have all seen how alcohol transforms people who consume it too much and/or too often.


On the other hand, wine is made from grapes, which contain many health-promoting phytochemicals, and there is also enough research to show that wine can improve, for example, heart health.

So – Is wine bad or good for health?

The answer is – it depends… It depends not only on how much or how often we drink wine but also on our lifestyle, genetics, gender, weight and many other factors.


In addition, it should be remembered that studies are varied, and their results often suggest an association but do not show causality, for example:

  • Descriptive studies – surveys and questionnaires. These studies are conducted to identify associations and explore relationships, but they cannot establish causality. For example, people who drink Diet Coke tend to take in more calories during the day. This may be true, but we do not know whether the increased calorie intake is due to Diet Coke or something else.
  • Randomised controlled trials are considered the gold standard of research. To assess the effect of an intervention (e.g. the effect of specific substances, products, etc.), study participants are randomly allocated to treatment and control groups. The studies aim to establish cause and effect relationships, e.g. Cola containing phosphoric acid causes a decrease in bone mineral density, which may lead to a higher risk of osteoporosis.
  • Review studies:
    • Systematic reviews that critically analyse existing research on a specific topic. These are often used to build evidence-based practice.
    • Meta-analyses combine data from several studies to obtain a more precise estimate of a particular effect.

Why am I telling you all this?

To make you understand that, when it comes to nutrition, you can “prove” almost anything by focusing on the results of just a few descriptive studies or not telling the whole story.

This is why I include a list of sources/studies in all my articles – so that any reader of the article can also judge for themselves how accurate my conclusions and recommendations are.


Calories are not the only problem

If you drink two cans of regular cola (2 x 330ml or 2 x12oz) every day, you are consuming around 280 ’empty’ calories. That’s about 8400 calories per month, which, if not used up during physical activity, turns into about 900 g of fat (1 g of fat = 9 calories).

In other words, if a person likes Coke and does not do hard physical work, there is at least one good reason to start drinking Diet Coke instead of regular Coke.


The worry is that artificially sweetened diet lemonades may trigger cravings for sweet and calorie-dense foods so that the number of calories consumed during the day may increase rather than decrease.


Animal studies have shown that at least one artificial sweetener (aspartame) damages the part of the brain that signals the animal when to stop eating.


Several human studies have found that people who drink artificially sweetened drinks tend to gain weight.



Many other randomised controlled trials have found that artificially sweetened low-calorie drinks can help reduce weight.


Studies on calorie-free drinks in relation to weight loss are also complicated by the so-called “reverse causality”. In other words, people who are at risk of obesity, choose calorie-free drinks, and from the outside appears that the weight gain is caused by these drinks.

And, of course, the numerous studies on artificial sweeteners and the possible health problems associated with them. However, there is still no conclusive evidence that artificial sweeteners can increase the risk of certain cancers, cardiovascular diseases, kidney problems, etc. etc. etc.


Is it better to drink carbonated water without artificial sweeteners?

Carbonated water drinks without artificial sweeteners have long been considered safe – what can happen if the drink contains neither sugar (calories) nor artificial sweeteners?


However, there is one study in rats and humans that calls this view into question.

Let’s start with rats.

Male rats were divided into four groups, and each group was given one of four drinks for more than a year: water, non-carbonated drink with sugar, carbonated drink with sugar, and carbonated drink with artificial sweetener.

The results were really surprising:

  • The rats that drank the carbonated drinks (whether with sugar or sweetener) ate more than the rats that drank water or the non-carbonated drink with sugar;
  • Rats that drank carbonated beverages (whether with sugar or sweetener) gained weight faster than rats that drank water or non-carbonated beverages with sugar;
  • The amount of ghrelin (a hormone that controls hunger) in the stomach tissue was higher after drinking carbonated drinks (compared to rats drinking non-carbonated drinks).

And now for humans.

20 male students drank five drinks a day for one month (the same as the rats: water, non-carbonated lemonade with sugar, carbonated lemonade with sugar or carbonated lemonade with sweetener). Soon after, their blood ghrelin levels were measured.

When they drank any carbonated beverage, their ghrelin levels rose higher than when they drank water or lemonade without gas.

Although this study did not assess the students’ food consumption or weight changes after drinking the different drinks, the elevated ghrelin levels after drinking carbonated beverages suggest that these drinks may trigger hunger, increased food consumption and subsequent weight gain.

Why might drinking carbonated beverages contribute to ghrelin release?

The study authors suggest that pressure-sensitive cells in the stomach increase ghrelin release in response to the carbon dioxide in carbonated drinks.


So, what to drink when losing weight?

The answer is simple – water. Unsweetened tea, water with lemon, cranberries, mint leaves…. are also good alternatives.


Key takeaways

Although pure water is the best drink from a health point of view, it is not the favourite drink for many people.

That’s why.

If you like lemonade, it’s a good idea to switch from regular to a calorie-free alternative. Diet (calorie-free) fizzy drinks can also be a reasonable choice, as long as you make healthy eating choices every day and monitor your weight regularly.

There is a real possibility that carbonated beverages may have an underestimated negative effect on appetite and weight. However, it would be premature to say we should all give up carbonated beverages.

The artificial sweeteners and other chemicals currently used in diet lemonades are safe for most people, and there is still no credible evidence that these ingredients cause cancer or other health problems.

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