Sugar Substitutes are Associated with Weight Gain - Here’s Why.

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artificial sugars-196923-editedSugar substitutes like sucralose, sugar alcohols (xylitol, erythritol, sorbitol), aspartame, acesulfame-K, neotame, & saccharin offer a sweet taste without the associated calories. 

These sugar replacements have been championed by the food industry (red flag alert) as the solution to having your soda, ice cream, or cereal bar - without the calories!

If it sounds too good to be true - chances are you’re right.

Does switching to these sugars actually help people lose weight?

In a “calories in, calories out” doctrine of weight loss - the use of non-caloric sugars “should” lead to improved weight management.

But does the consumption of the sugar substitutes make the cut for weight loss?

The answer is an emphatic NO!

Non-Caloric Sweeteners for Weight Loss - Not so Fast!

Use of artificial sweeteners & sugar alcohols has sky-rocketed alongside the rise in obesity (see chart 1). Causal arguments have been made in both directions - the sugar substitutes lead to obesity, obesity leads to higher sweetener use. The causation doesn't matter.

Chart 1: Obesity has risen alongside the use of artificial sweeteners

artificial sugars and obesityPhoto Credit: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892765/

It is consistently clear is that artificial & non-nutritive sweeteners are not reducing weight in any meaningful way.

I scoff when I see “light” & “sugar-free” labels on products.

The food industry simply claims that the replacements are for use in people who desire to limit their sugar intake - so they’re conveniently not making direct weight loss claims.

The indirect claim perceived by the public is the use of these sweeteners helps with weight loss.

Exploring the Evidence for Weight Gain with Sugar Substitutes

sugar substitutes and obesityWhile artificial sugars are marketed as weight loss tools, the research clearly shows that they are not associated with weight loss (1; 2; 3)

The evidence dates back more than three decades.

  • In 1986, a study looked at a cohort of 78,694 women and their use or non-use of artificial sweeteners. Over one year, users of artificial sweeteners were more likely to gain weight than non-users - independent of their starting weight (4)
  • A study published in the American Journal of Clinical Nutrition in 1990 followed a group of 31,940 women over eight years. Saccharin use was correlated with weight gain over the 8 years (5).
  • In 2008, the San Antonio Heart Study followed 5,158 adults over the subsequent 7-8 years. Follow-up investigations were conducted on 3,682 of the patients. The higher the intake of artificially sweetened beverages - the higher the measures of BMI in study participants - even after controlling for gender, ethnicity, starting BMI, and diet (6)!
  • Similar findings have been demonstrated for children drinking diet soda (7; 8; 9). In cases where weight loss was discovered, the loss was attributed to total calorie restriction - not the use of the sweeteners (10).

Mechanisms of Action - Why Artificial Sweeteners Lead to Weight Gain

We established that sweetener use is correlated with statistical weight gain, not weight loss (11). Making matters worse, sugar substitutes have also been associated with the development of obesity, type 2 diabetes & cardiovascular disease (12).

There are a number of proposed reasons why this happens.

  1. Decreased Satiety: Because the sugars are unnatural, they may not trigger the same satiety signals as other food sources.
  2. Higher Total Calorie Consumption: The higher consumption may be a result of altered satiety, but a more likely cause is “calorie compensation”. Compensation occurs when someone feels they can eat more because they “behaved” well with their previous choices (13)
  3. Higher Inflammation: Consumption of sucralose was associated with pro-inflammatory gene expression in mice over 6 months (14). A recent study showed that artificial sweeteners can be toxic to gut bacteria (15).
  4. Altered Microbiome and Impaired Glucose Tolerance: The main driving force seems to be the changes in the gut microbiome & glucose tolerance.  (16; 17; 18). These changes also increased the presence of lipids, fatty acids, and cholesterol - and decreased useful metabolites normally produced by gut bacteria (19). It is the changes in microbiota that then increase the risk of chronic diseases such as obesity, type 2 diabetes & cardiovascular disease (20).

Eliminating artificial sweeteners is an important aspect of microbiome restoration - you might do all of the right things, and the limiting factor in your success could be artificial & replacement sweeteners in your diet!

Why Changes to the Gut Microbiome Take the Cake for Weight Gain:

intestinal health-1Gut bacteria play an essential role in how much energy we extract from our food (21).

When we eat artificial sweeteners, they increase groups of bacteria that are more efficient at taking energy from our food and turning it into fat.

Weight changes in the microbiome are rapid and transmissible across generations (22).

This is game-changing!

The discovery undercuts the entire “calories in, calories out” model of weight loss that’s been around for decades.

Calorie intake matters less - what your gut bacteria do with those calories matters most.

The new weight loss mantra should be:

Fix your gut -fix your weight!

Sugar Alcohol Metabolism:

Sugar alcohols are not often discussed alongside artificial sweeteners like sucralose. The research still suggests a detrimental effect of sugar alcohols on gut microbiota & motility.

Sugar alcohols (xylitol, sorbitol, erythritol) are not broken down by the body and are eliminated as waste. They add sweetness to food, but because they’re not metabolized - they are considered non-caloric.

When the sugar alcohols make it to the intestines, bacteria try to break them down, and the confusion drives changes in the gut flora (23).

Because sugar alcohols make it to the colon undigested - they also attract water - increasing the incidence of diarrhea, bloating, distention & general GI discomfort.

If you find sugar alcohols in your shake & drink mixes - find an alternative unless you or your health professional determine the other benefits outweigh the poor effect of the sweeteners.

A small amount can be tolerated - but if you’re looking to heal the gut - it’s best to stay away until other aspects of your gut health improve.

What Sugar Substitute Should I Use?

The one sugar substitute that I like using & approve at the time of this writing is Stevia leaf. I use the liquid, but it is also available as a powder.

Stevia is a natural plant extract that does not appear to run into the same problems as other non-nutritive sweeteners. It is my top choice.

The jury is not completely out on stevia, but it looks pretty positive as it stands now. There is evidence for added stevia benefits to the microbiome as a natural antibacterial, anti-Lyme & anti-biofilm agent.

So not only can it help you enjoy a little sweetness in your life - it may also help improve your gut flora.

I know of many colleagues who carry stevia with them to restaurants to add to their unsweetened teas and other beverages while at conferences. I keep it on hand at home.

I use stevia most regularly in tea, smoothies & homemade sorbet.

If you want to avoid the problems associated with other sugar substitutes, use stevia instead!

What Natural Sugars Should I Use?

I’m comfortable with natural sources of sugar such as local raw honey, blackstrap molasses & maple syrup - unless…

  • Your weight loss efforts have plateaued
  • You’ve already been diagnosed with impaired blood sugar
  • You’re following a special diet such as low-FODMAP or Specific Carbohydrate Diet.

These naturally-derived sweeteners contain healthy vitamins, minerals, pollen, and botanical substances that provide some extra benefit beyond their sweet taste.

I do not like agave syrup - it is richest in fructose which is tough to digest as it requires action by the liver & aggravates weight loss efforts. Excess fructose contributes to fatty liver disease, blood sugar imbalance & diabetes.

A little agave in coffee and tea is not the worst thing for you - but I just don’t like having it on hand because you’ll find multiple ways to use it.

wine health benefits

Sugar in Alcohol & Wine

Alcohol can be a source of sugar and carbohydrates in your diet. Drinking your calories is a sure fire way to gain weight.

I do like straight tequila as a “clean” source of alcohol due to its botanical residues - and some approve its use even for diabetics.

Red wine is often highly touted as an anti-aging strategy. The polyphenols in red wine do have some benefits for gut health - yet many wine varieties are very sweet.

“But wine has resveratrol!”

I do not believe that you get enough of the anti-aging ingredient resveratrol to get overly excited. The entire array of polyphenols may be more exciting, yet individuals seldom keep it to one glass.

“But studies show that wine drinkers live longer!”

This evidence is still correlative. Wine drinkers also come from higher socioeconomic backgrounds and share many other healthy habits. It also may reflect social connectedness  & more meals made fresh at home - stronger predictors of longevity.

Recent research has suggested that no amount of alcohol is healthy (24) - so tequila & red wine lovers beware!

Drink responsibly my friends.

The Trouble with Fructose Intake

fructose and liver healthHigh fructose intake can drive imbalances in gut flora at high intakes as well as potentiate bacteria imbalance & liver congestion.

High fructose corn syrup really aggravates these problems, but regular fructose will do the same with enough dose. Eating lots of vegetables balances your fructose intake from fruit sources.

Aim for a ratio of 4-5 servings of vegetables for every serving of fruit - with a minimum ratio of 2:1. When you do the math, this allows for 1-2 pieces of fruit a day. More fruit is allowed for those with high physical activity like athletes.


If you suspect you suffer from “fructose intolerance” (sudden bloating, discomfort, & gassiness after consuming fructose) - this is more indicative of a gut flora imbalance than a problem with fructose directly.

It means you might need to take a break from all sources of fructose - and add them back in carefully after you fix your gut bacteria.

Fructose is technically a liver toxin (25) - and so while you can tolerate some without trouble - fructose-containing syrups and sweeteners quickly exceed your body’s capacity to metabolize it efficiently. 

How much more fructose are we consuming than we should? The average American consumes five times the amount of fructose than what was consumed in the late 1800's. So we're eating at least 500% more than what is natural.

The body shovels the excess energy as fast as it can into fat storage - starting in the liver first - congesting all of the liver’s important functions. Then we start depositing extra fat around the mid-section - increasing dreaded belly fat - and the cardiovascular health risks associated with it.

Cardiovascular disease is still the number one cause of death - I blame sugar, not fat, and I think you should too. There's even some professionals that claim fructose is the primary source of our obesity epidemic - consume it wisely.

Elevated Triglycerides & Belly Fat as Early Signs of Trouble

High triglycerides in the blood may seem to be an issue with fat intake - but it’s actually a sign of excess sugar not being able to make it into the liver efficiently to be processed into energy.

If you have high triglycerides, you’re eating too much sugar!

As a rule of thumb, the more unhealthy belly fat you have, or the higher your fasting triglyceride levels, the more you should limit your fructose (& sugar) consumption - even if your blood sugar has measured in a healthy range.

NOTE: Honey, molasses, and maple syrup contain fructose too, so these should still be used sparingly & you might limit them as well until your metabolic state improves.

Take home message: Eat real food, enjoy alcohol wisely & when your sweet tooth starts calling your name, use a little stevia or natural sugar sources.

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Dr Alex Rinehart

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