Introduction
Whether it is health warnings by the WHO or Saccharin bans, sugar substitutes are polarizing. Quick alarming fact: Romans used lead pots or lead alloys to help make wine-sweetening agents. In fact, Lead(II)acetate is considered one of the first sugar substitutes, which is a pretty horrific thought. Given these factors, it’s understandable why sugar substitutes face so much scrutiny.
As overall food consumption has increased, so has a need to satisfy our desire for sweetness without calories — hence the increasing use of sugar substitutes. In this article, we cover whether using sugar substitutes for weight loss is helpful and what to look out for when utilizing them as part of weight management.
Let’s dig in.
What is a sugar substitute?
For this article, we are using sugar substitute as a catch-all term, which includes but is not limited to low-calorie sweeteners or non-nutritive sweeteners. We aren’t using the term artificial sweetener because not all of these sweeteners are “artificial,” but they aren’t all non-nutritive. In truth, there’s probably a need for a better umbrella term. Still, the purpose of this article is that the general label of sugar substitute suffices.
These are a few of the common sugar substitutes:
| Sweetener | Type | Origin |
|---|---|---|
| Acesulfame K | sugar substitute | Acetoacetic acid & potassium |
| Allulose | low-calorie sweetener | Extracted from plants like corn or wheat as well as fruits |
| Aspartame | sugar substitute | Aspartic acid & phenylalanine (amino acids) |
| Erythritol | sugar alcohol | Fermented from corn or glucose |
| Monk fruit | non-nutritive extract | Monk fruit extract |
| Saccharin | sugar substitute | Historically: Coal tar derivatives (some countries may still use this method) Currently: Methyl anthranilate or phthalic anhydride (petroleum-based) |
| Stevia | natural non-nutritive | Stevia plant leaves |
| Sucralose | sugar substitute | Modified sucrose (table sugar) |
| Xylitol | sugar alcohol | Derived from birch trees |
How are sugar substitutes hypothesized to help with weight loss?
The goal of most weight loss is to decrease body fat. Since fat loss occurs when you consume fewer Calories than you expend, adding sugar substitutes to your diet could be a way to reduce total Calorie intake. For example, if you usually drink tea with sugar, which adds around 110 Calories per cup, switching to a sugar substitute that contains only 5 Calories can help reduce daily Calorie intake. Over time, consistently making these swaps could lower overall energy intake and support fat loss.
At its base level, if sugar substitutes help you eat fewer Calories and lose body fat, they serve their purpose because that’s really all they’re meant to do. They’re not trying to stoke or alter your metabolism, it’s just replacing something with higher Calories with something with little to no Calories. That might seem an overly simplistic statement, but it’s a bit of a controversial one.
So, do sugar substitutes actually make a difference?
A quick look at research methods and causality
You’ve probably seen many conflicting outcomes if you’ve ever explored sugar substitute research. Does it help weight loss? Does it cause weight gain? We’ll explore these questions, but before we do, it helps to understand how studies are designed, which can determine the types of conclusions we can draw from them.
Typically, research is divided into observational and experimental studies. In observational studies, we “observe” and collect data on participants. This can involve tools like surveys, self-reports, or food diaries. Experimental studies are more hands-on and involve researchers manipulating an independent variable to test a hypothesis.
Observational studies allow us to draw associations between variables and outcomes, but they don’t tell you something caused a particular outcome. When you see an association in observational research, you could be dealing with a causal relationship (the variable you observe causes the outcome you observe). Still, you could also be dealing with a confounded relationship (the variable and the outcome are both causally related to a third variable). For example, ice cream sales are associated with drowning, but ice cream doesn’t cause drowning. Instead, people tend to buy more ice cream and spend more time near the water when it’s warm outside, so the conditions that increase ice cream sales also increase the rates of drowning, an association without any causal link or even reverse causation. Reverse causation is when the presumed “outcome” is actually the causal factor impacting the variable of interest, not the other way around.
Reverse causality can happen when we misinterpret the relationship between events. This means we think A is causing B, but B could actually cause A. Here’s a very simple example: let’s assume that we had a dataset of people at least 7 feet tall, and we were doing an observational study to determine how they got so tall. One of the variables in the dataset is “profession,” and we observe that people who are 7 feet tall are disproportionately likely to be professional basketball players. So, we conclude that being a professional basketball player makes you taller. But of course, that’s nonsense! There is a causal relationship at play, but it goes in the opposite direction. Being a professional basketball player doesn’t make you taller. Instead, being taller is often a significant advantage in basketball, so tall people are disproportionately likely to become professional basketball players.
Now, let’s return to the topic of this article. Suppose we observe people with higher body fat and notice they are drinking a lot of sugar substitute beverages. In that case, we ask, “Does substituted sugar consumption lead to fat accumulation? Or are people with higher body fat levels more likely to use sugar substitutes in an attempt to manage their weight?”
To test whether sugar substitutes cause weight gain (or weight loss), we need randomized controlled trials (RCTs) to filter out variables and see more direct relationships. A well-designed RCT does allow us to more confidently establish causal relationships, and the direction of causation. In this example, if sugar substitutes cause weight gain, that should be easy to test: have one group of subjects consume sugar substitutes, have another group abstain from sugar substitutes, and then see whether the subjects consuming sugar substitutes start gaining more weight than the abstainers.
Why this mini-lesson on study types and reverse causality?
If you’re reading this article trying to understand if you should embrace sugar substitutes or eliminate their use from your world, there’s a chance you could already have been swayed by studies like these that state sugar substitutes are related to a higher volume of visceral, intermuscular, and subcutaneous adipose tissue. Not the best PR for non-nutritive sweeteners.
The CARDIA study above was part of sugar substitute’s rough 2023. The prospective cohort observational study followed people over time to see how their diet and body compositions progressed through the years. Using a dietary recall questionnaire, researchers assessed participants’ dietary intake at three points: baseline, year 7, and year 20. Within that recall, participants reported details about their food intake, including whether it contained sugar substitutes. The study concluded that higher sugar substitute intake was associated with greater fat accumulation in all measured areas.
In a 2016 paper, Drewnowski and Rehm used a cross-sectional analysis of 22,231 adults with self-reported 24-hour dietary recall from five different surveys conducted over 10 years. The study included sucralose, aspartame, and saccharin and examined foods and liquid beverages containing these sweeteners, such as diet sodas.
Similar to the CARDIA study, they found associations between sugar substitute use and body composition. However, rather than linking sugar substitutes to weight gain, they discussed the possibility of reverse causality and found that sugar substitute use was tied to weight control behaviors. This means that people who consumed sugar substitutes were more likely to be trying to lose or maintain weight, which the researchers found held true even after adjusting for BMI.
The authors note, “The relation between weight loss/maintenance intent and current LCS (low-Calorie sweeteners) use was not unique to obese individuals but held at all levels of BMI. That would suggest that LCS use was tied directly to dieting behaviors, regardless of whether the participants were overweight or obese. This new finding suggests reverse causality, linking LCS use with trying to lose or maintain body weight.”
Instead of assuming sugar substitutes cause weight gain, a more plausible explanation is that they are more commonly used by people actively trying to manage their body weight. The Drewnowski and Rehm paper highlights this, emphasizing that sugar substitute use is associated with weight control efforts but not necessarily weight gain or loss itself.
So now we can dive into more direct experiments: Can sugar substitutes help decrease body fat, and are there more direct experiments that address this question?
Do sugar substitutes help with weight loss?
Let’s start with a randomized controlled trial that examined weight loss when replacing sugar-sweetened beverages with either water or a sugar substitute diet beverage. This pretty straightforward RCT compares three groups: one receiving general dietary advice (targeting ~100 fewer Calories per day), one replacing sugary drinks with water, and one replacing them with diet beverages.
Both the water and diet beverage groups had similar weight loss results, with a slight edge for the diet beverage group.
Now would be a good time to mention that water also performs well when comparing Calorie replacement. When water and sugar substitutes compete, they tend to be pretty close (here and here). To me, this heightens the importance of replacing Calories as a method of achieving weight loss, but I wouldn’t go as far as to say that sugar substitutes had some great advantage other than personal preference and helping with adherence.
Let’s turn to a systematic meta-analysis that pools multiple trials together to get a broader perspective. This analysis examined six randomized controlled trials on the effects of replacing sugar-sweetened beverages with non-caloric alternatives. Tobiassen and Køster-Rasmussen looked at six different studies with a total of 1,729 participants and at least a 6-month follow-up. It showed a small BMI reduction of about 0.31 kg/m² when you replace a sugar-sweetened beverage with a non-Calorie option, and that sugar substitute beverages performed pretty similar to water.
So, it would seem that there’s decent evidence to suggest that, at the very least, substituting Calories with non-Calories helps weight loss. Sugar substitutes can be part of those non-Calorie choices and help with adherence. While some studies show that sugar substitutes increase weight, they have noted criticism of reverse causality and involve more observational studies and fewer RCTs. This brings us full circle as to why these factors matter in the studies we are discussing on this topic.
Are there any cons to using sugar substitutes for weight loss?
Let’s take a look at a few of the purported reasons we might want to be careful with our use and consumption of sugar substitutes.
Gut health and metabolic effects
The biggest concern often discussed is whether sugar substitutes negatively alter the gut microbiome. The gut microbiome is a collection of bacteria and other microorganisms (even fungi and viruses) that play a role in digestion and, by proxy, our immune and metabolic health.
To be clear, the number of things that can alter the gut microbiome is kind of endless. Our diet, sleep, and stress are just a few. The types of fiber we eat or getting a common cold can change it temporarily or for years. We are currently in a place of research where we are gathering a lot of data. With sugar substitutes, it’s just too early to call, and the studies appear to be mixed in outcome.
Additionally, sugar substitutes don’t seem to provide any negative metabolic effects and could offer some positives (including possible gut benefits). It’s also important to evaluate individual sweeteners separately rather than treat them as a single category while considering your experiences and responses.
Some sugar substitutes can have Calories
If I’m going to credit sugar substitutes for reducing Calorie intake, I also have to acknowledge some can add Calories. I don’t bring this up to encourage obsessive calorie counting, but rather because I’ve seen enough heavy use of these products to know that, for a small few, it’s worth mentioning.
Not all sugar substitutes are entirely non-Caloric. Some are combined with bulking agents that contain Calories, even if the sweetener itself does not. In small amounts, this isn’t a major concern, and most of the time the impact is negligible. But if you’re using them in larger quantities or have a lower total daily energy expenditure, those Calories can add up.
Granulated Splenda, for example, is a sucralose sweetener and one of the better-tasting sugar substitutes. However, its first ingredient is maltodextrin, a white powder carbohydrate that helps with baking texture. The packet version of Splenda contains dextrose as well, which is actually a type of sugar, so, in a funny twist, the secret ingredient to most people’s favorite fake sugar is sugar. The weight ratio is important to consider because a cup of Splenda weighs significantly less than a cup of sugar and, therefore, has far fewer Calories — but they both equal roughly 3-4 Calories per gram. Again, if you use it in small quantities, there’s no need to give it much thought. But it’s something to consider if it’s making up decent portions of your daily intake (just to put some explicit numbers on it, one cup of sugar weighs about 200g and contains about 800 Calories. One cup of granulated Splenda, on the other hand, weighs about 25g and contains 75-100 Calories).
While aspartame contains 4 Calories per gram, its intense sweetness means only a tiny amount is used in products. Unlike mixed sucralose products like Splenda, it would be much harder to consume a noticeable amount of Calories from aspartame alone. For example, a 12-ounce Coke Zero contains just about ⅓ of a Calorie, which is essentially negligible. Xylitol, on the other hand, has roughly 2.5 Calories per gram and is best thought of as a “sugar-lite” option.
Overall, I think this is mostly a non-issue, but being informed about it is a good idea.
Food relationships
Another steady argument against sugar substitutes is that they reinforce a preference for sweet foods, making it harder to reduce sugar intake. The idea is that consuming sugar substitute foods prolongs a “sweet tooth” and decreases the likelihood of cutting back on sugared foods altogether.
However, research doesn’t strongly support this claim. While there are interesting discussions about how exposure to certain flavors influences dietary habits (which could have more to do with our base taste preferences than dietary habits), there’s little evidence that sugar substitutes hinder the process of flavor exposure. Studies on sweetness exposure suggest that consuming sweet-tasting foods, whether artificially or naturally sweetened, does not consistently increase a general preference for sweetness. In fact, short-term exposure to sweet tastes could reduce the desire for more sweetness, and this appears again to be a neutral or beneficial effect on weight loss. Therefore, the notion that sugar substitutes keep people “hooked” on sugar doesn’t seem to be supported.
Closing thoughts
These studies show that sugar substitutes have a neutral to positive effect on weight loss and maintenance. Many people use them to help reduce Calories; for some, this could be a helpful weight management aid. While there’s a clear relationship between sugar substitute use and weight loss efforts (which makes sense), there is no indication that these sweeteners lead to weight gain. Instead, they may support dietary behavior changes that contribute to weight loss.
If you’re using sugar substitutes to help cut Calories, moderate use appears to be fine. While I wouldn’t recommend excessive intake, small amounts can make it easier to stick to a diet, especially if they help you avoid feeling overly restricted. Do they offer more than that? Probably not. But for some, that’s enough to make meaningful change.
