Do Sugar Free Sweeteners Make You Fat?

Do Sugar Free Sweeteners Make You Fat?

For many years people have been drinking sugar free drinks or eating sugar free foods to lose weight. Does it work? Or is it possible sugar free sweeteners make you fat?

A recently published study looking at 10 years of sugar free sweetener use shows there may be a strong correlation between their use and weight gain. You read that right… not weight loss but weight gain.

However, before we take that as gospel you need to understand some basics of weight loss and weight gain. You also need to understand the difference between correlation and causation studies. There are definitely some cause for concern and if you want to know the truth about sugar free sweeteners and the impact on your waistline and your health then read on...


Insulin and its role in Weight Gain

Many people don’t truly understand the role of insulin and therefore don’t fully appreciate the powerful nature it has on body composition and health. Insulin is a critically important hormone responsible for removing excess sugar from the blood.

It helps to transport glucose (sugar) into your muscles, liver and fat tissue. It does this because excessively elevated blood sugar levels can cause severe health problems. Insulin, when chronically released may result in a condition called Metabolic Syndrome (see image below).

The Metabolic Syndrome


Metabolic Syndrome is a set of health disorders that can often lead to obesity.

Insulin is also a pro-inflammatory hormone that may cause a cascade of mental and physical health issues. Most importantly while insulin is present, lipolysis (fat burning) cannot take place. So, if you are chronically releasing insulin due to poor dietary choices (processed carbs, sugars etc), then you may become insulin resistant or type 2 diabetic.

Once you become insulin resistance in muscle then your body produces even more insulin as your sensitivity to it becomes decreased, therefore even less fat burning takes place due to chronically high levels of insulin in your blood. However, your fat tissue stays insulin sensitive and will take up all the carbohydrates you keep eating and turn them into adipose tissue (fat). As you can see it’s a vicious cycle.

Note: Carbohydrates release the most amount of insulin, followed by protein, while fats and ketones do not release insulin at all.

Eating fats or protein with carbohydrate foods may slow the rise in blood sugar levels and reduce the need for a lot of insulin. This is also why low glycaemic foods make better choices as less insulin is released to manage the utilisation of the nutrients you consume.

Note: Ketones improve insulin sensitivity and reduce the release of the hunger hormone ghrelin. So this keeps you feeling fuller for longer.

Managing insulin and maintaining a stable blood sugar level is one of the healthiest ways to burn fat and reduce inflammation.

Why am I telling you all of this? Because the suggestion circulating the internet is sugar free sweeteners make you fat because they release insulin like their sugary counterparts.


Do Sugar Free Sweeteners Stimulate The Release Of Insulin?

In living breathing humans no! However, an in vitro (petri dish) study of rat pancreas and an in vivo (living animal) rat study with infused (not consumed) Ace-K (Acesulfame Potassium) sugar free sweetener showed a mild rise in insulin (1).

But let me remind you… you are not a rat and you do not inject your sweeteners!

There are many human clinical trials assessing the impact sugar free sweeteners have on insulin and other hormones that may impact fat loss or gain (2,3,4,5,6,7,8) and they conclusively show no impact on insulin or other hormonal changes like ghrelin (hunger), growth hormone, cortisol etc.

This is great news because it means sugar free sweeteners do not contribute to metabolic syndrome through the release of insulin and will not shut off fat burning as a result.

However, there is evidence that some artificial sweeteners (not stevia) may disrupt the gut microbiome which can lead to weight gain and other health challenges. Stay tuned, we will cover this in an upcoming blog!

So, if sugar free sweeteners don’t impact insulin. How do they contribute to weight gain? Or do they?


Do Sugar Free Sweeteners Increase Cravings For Sweets?

The argument that sugar free sweeteners (including stevia) may increase cravings for sweet foods by stimulating the part of the brain (Hypothalamus) that controls hunger is worth discussing.

When you consume something sweet your body may releases dopamine, which then stimulates the reward centre of your brain creating a hunger for said sweetness.

Generally, when you eat something sweet that contains calories the calories are processed, and the body slowly releases leptin (satiation hormone) which shuts off the hunger. But if there are no calories then leptin may not get released and you may continue to crave food. So, if you are drinking calorie free diet drinks or chewing calorie-free gum regularly then this may have an impact on your sweet cravings.

However, sugar free sweeteners used in protein shakes or amino acids that contain calories (although not from carbohydrates) won’t be a problem. In fact, amino acids (from protein) have been found to help control sugar cravings and promote fat loss.

An essential amino acid called L-phenylalanine is responsible for releasing cholecystokinin (CCK). CCK is a hormone released in the intestines after food enters the gut. Its role is to tell the brain you have food so can stop eating and focus on digestion.

Researchers have pinpointed brain cells called tanycytes which are found in the wall that lines the third ventricle of the brain. They are thought to transfer information between the brain and the cerebrospinal fluid and are known to sense glucose. New research indicates that they're also quite adept at sensing amino acids as well.

After exposing tanycytes from the brain tissue to the essential amino acid lysine they discovered that these cells released signals to the brain indicating satiety (fullness) within 30 second.

This is further support that amino acid and ketone supplements (which supress ghrelin) containing sugar free sweeteners are not going to leave you craving sweets. Especially if the sugar free sweetener is stevia.


What About Calorie Free Pre-workouts and Thermogenic Drinks?

While many pre-workout and thermogenic drinks contain no calories that doesn’t make them the same as diet sodas or gum since theses formulas have ingredients which help reduce cravings in other ways. Fat Burners and Pre-Workouts generally contain stimulants that increase the release of adrenaline. Adrenaline shuts off hunger.

When was the last time you were running for your life and had a craving for a Mars Bar or a Big Mac? Never right!! That’s because running for your life releases adrenaline and adrenaline shuts down your appetite. You can’t digest food while being physically active, so your body uses this feedback of adrenalin to control hunger.



Sugar free sweeteners don’t increase insulin or other hormones that may adversely affect your metabolism. However, many of them (except for stevia) may adversely impact your gut health (Blog coming soon).

They do not contribute to metabolic syndrome or type 2 diabetes through insulin secretion or increased cravings. However, they may increase cravings when consumed chronically without other ingredients like stimulants or amino acids.

So, what about the 10-year study? Often people who consume a lot of artificial sweeteners have a less healthy lifestyle and generally eat less nutrient rich wholefoods.

This unhealthy lifestyle may be the real contributor to weight gain or maybe it’s the disruption of the gut microbiome? Read our next blog coming soon to understand the gut health weight gain connection.


Take Aways

  • Leave your sugar free sweetener consumption for your Protein Shake, Amino Acids, Ketones, Fat Burners or Pre-Workouts.
  • If using supplements or food containing sugar free sweeteners, use a natural option like Stevia.
  • Try to minimise or eliminate diet drinks and chewing gum.
  • Do not replace your sugar free sweetened options with sugar full options unless your goal is to gain weight.


Disclaimer: The above article is merely a guide and is in no way a recommendation or a treatment protocol for any health conditions or diseases. You should always consult with a qualified health care provider before changing your supplement, training or nutritional strategy. Supplementation should not be attempted by pregnant or breastfeeding women, anyone on prescription medication or children under the age of 15 unless advised by your qualified health care provider.


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Effect of aspartame and protein, administered in phenylalanine-equivalent doses, on plasma neutral amino acids, aspartate, insulin and glucose in man.Møller SE1. Pharmacol Toxicol. 1991 May;68(5):408-12.

Aspartame and its constituent amino acids: effects on prolactin, cortisol, growth hormone, insulin, and glucose in normal humans. Am J Clin Nutr 1989 49: 3 427-32

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Effects of oral ingestion of sucralose on gut hormone response and appetite in healthy normal-weight subjects. Ford HE1, Peters V, Martin NM, Sleeth ML, Ghatei MA, Frost GS, Bloom SR. Eur J Clin Nutr. 2011 Apr;65(4):508-13. doi: 10.1038/ejcn.2010.291. Epub 2011 Jan 19.