Replacing sugar with low-calorie sweeteners can reduce your calorie intake, and may lead to weight loss.
However, some people claim that low-calorie sweeteners promote weight gain.
For this reason, a group of scientists assessed the overall evidence in a systematic review and meta-analyses of studies in both animals and humans.
Low-calorie sweeteners are widely used throughout the world. They can be added to food, but are also found in processed foods and diet sodas.
Low-calorie sweeteners might affect body weight in several ways:
- Calorie intake: Replacing sugar with sweeteners may cause you to eat more later on (4).
- Label awareness: When food or drinks are labeled as low-calorie, some people may eat larger portions, eat more of other foods or eat more later on (5, 6, 7, 8).
- Added sweetness: Sweetness might increase calorie intake by making foods more satisfactory or pleasant to eat (9).
- Energy balance: Low-calorie sweeteners may disrupt how the body associates sweetness with calorie intake, impairing energy balance (10).
A team of European researchers from the International Life Science Institute looked at how low-calorie sweeteners affect body weight and calorie intake.
This was a systematic review and meta-analysis examining the effects of consuming low-calorie sweeteners on calorie intake or body weight.
Several meta-analyses were conducted on different types of studies published before February 1st, 2015. These included intervention studies, randomized controlled trials, observational studies and animal studies.
Randomized, Controlled Trials (RCTs)
The review included 56 randomized, controlled trials or intervention studies that were divided into two categories, depending on their duration:
- Short-term: RCTs that were shorter or equal to one day in length.
- Long-term: RCTs that lasted for 10 days or longer.
The review included the results of 12 observational studies, but only nine were used in meta-analyses.
All of these were prospective cohort studies, which measured habitual intake of sugar-sweetened beverages or diet beverages at one time point, and then followed the participants for more than one year.
This allowed the researchers to find out if sugar or low-calorie sweeteners were associated with changes in body weight.
The researchers reviewed 62 articles, which reported the results of 90 studies examining the effects of low-calorie sweeteners on mice or rats.
These studies were divided into three groups, depending on their purpose:
- Forced consumption: These studies examined the effects of forced consumption of low-calorie sweeteners.
- Voluntary consumption: These studies examined the effects of voluntary consumption of low-calorie sweeteners.
- Learning studies: These studies tested the hypothesis that rats fed low-calorie sweeteners will stop associating sweetness with additional calories.
Bottom Line: This analysis combined the results of randomized controlled trials, observational studies and animal studies published before 2015.
Finding 1: Low-Calorie Sweeteners Reduce Short-Term Calorie Intake
A total of 56 randomized, controlled trials, or intervention studies, lasting less than one day, were included in this systematic review.
These studies examined the effects of consuming low-calorie sweeteners on subsequent or total calorie intake.
The results of these studies were combined in a meta-analysis. Their main results are presented below.
Low-Calorie Sweeteners vs. Sugar
The meta-analysis showed that consuming low-calorie sweeteners, rather than sugar, significantly reduced overall calorie intake in both adults and children.
In addition, the analysis found that people tended to compensate for the reduced calorie intake by eating more at a subsequent meal. However, the calorie compensation was only partial.
Low-Calorie Sweeteners vs. Unsweetened Beverages/Food
Beverages or foods sweetened with low-calorie sweeteners did not significantly affect calorie intake, compared to the same foods without low-calorie sweeteners.
Similarly, diet beverages did not significantly affect calorie intake, compared to water.
Low-Calorie Sweeteners in Capsules vs. Placebos
When low-calorie sweeteners were given in capsules, they tended to reduce calorie intake, compared to placebo capsules.
One study found that taking a capsule containing aspartame, an amount similar to that found in diet sodas, reduced calorie intake, compared to a placebo (11).
The reason for these effects is unknown.
Overall, these studies consistently found that eating low-calorie sweeteners instead of sugar before a meal significantly reduced short-term calorie intake. On average, the difference was 94 calories.
The effects of eating low-calorie sweeteners were similar to drinking plain water.
Bottom Line: The results of short-term intervention studies suggest that consuming low-calorie sweeteners reduces short-term calorie intake.
Finding 2: Low-Calorie Sweeteners Reduce Long-Term Calorie Intake and Body Weight
This systematic review included a number of long-term intervention studies, ranging from 10 days to 3 years.
Nine intervention studies reported results for calorie intake.
A total of 10 long-term, interventional studies examined the effects of low-calorie sweeteners on body weight.
Five studies showed that consuming low-calorie sweeteners had significant benefits:
- One study of obese women linked consuming aspartame-sweetened foods and beverages to greater weight loss and less weight regain (15).
- Another study linked sugar supplements to increased calorie intake and weight gain, while artificial sweeteners had no adverse effects (12).
- An aspartame-sweetened beverage reduced body weight in men, but not women. The same beverage, sweetened with high-fructose corn syrup, increased body weight (20).
- This 18-month trial in children found that replacing sugary soda with diet soda reduced body weight and fat accumulation (21).
- A 12-month weight-loss trial showed that drinking an artificially sweetened beverage led to greater weight loss than plain water (22).
These studies were combined in a meta-analysis, which found that consuming low-calorie sweeteners led to a smaller weight gain, or greater weight loss, than sugar.
In short, the meta-analysis showed that eating low-calorie sweeteners caused a significant weight loss of about 3 lbs (1.35 kg).
Bottom Line: The meta-analyses of the RCTs showed that consuming low-calorie sweeteners reduced calorie intake and body weight.
Finding 3: Observational Studies Provide Inconsistent Results
A total of 12 observational studies examined the effects of diet sodas on body weight.
Overall, the results were mixed:
- Higher risk of obesity: Five studies found that diet sodas were associated with a higher risk of obesity (3, 25, 26, 27, 28).
- Lower risk of obesity: Six studies showed that diet sodas were linked with a lower risk of obesity (29, 30, 31, 32).
Meta-analyses combining the results from nine of these studies found no significant associations between diet sodas and changes in body mass index (BMI).
However, inconsistencies in the studies’ findings make it difficult to interpret the results. Additionally, observational studies cannot prove causation.
Bottom Line: The observational studies provided inconsistent findings. The meta-analysis found no significant links between low-calorie sweeteners and BMI.
Finding 4: Low-Calorie Sweeteners Do Not Affect Body Weight in Animals
The majority of animal studies suggest that eating low-calorie sweeteners does not affect body weight.
The review included 45 articles on 47 studies where rats or mice were fed specific amounts of low-calorie sweeteners.
The majority of the studies found no significant effects of low-calorie sweeteners on body weight.
However, 18 studies that used higher doses showed that low-calorie sweeteners decreased body weight. Conversely, a few studies reported significant increases in body weight:
- One study showed that saccharin increased body weight when it made up 1% of the diet, but higher doses had no effects (33).
- Other studies, using lower doses of saccharin, also found no significant effects (34, 35, 36).
- When saccharin, cyclamate, acesulfame-K or aspartame were added to drinking water, only saccharin and cyclamate significantly increased body weight (37).
- Another study found that low doses of cyclamate caused significant weight gain, but later studies were unable to replicate these findings (38, 39, 40).
The review included 10 articles, reporting the findings of 21 studies in which rats were given the chance to eat artificial sweeteners.
However, a few studies found that adding saccharin (0.2%) to water-mixed lab chow led to significantly greater calorie intake and weight gain (46).
Another study found that yogurt sweetened with aspartame or saccharin caused greater calorie consumption and weight gain, compared to yogurt sweetened with sucrose (47).
The review included seven articles discussing 22 learning studies.
A total of 14 studies (64%) showed that rats with access to food with low-calorie sweeteners gained more weight than those with access to glucose-sweetened food.
The relevance of these studies for humans remains unclear.
Bottom Line: When low-calorie sweeteners improve the taste of food, they may increase body weight in animals. However, the majority of studies suggest that low-calorie sweeteners, on their own, do not affect body weight.
This systematic review and meta-analysis had a few limitations.
First, it did not differentiate between the various types of low-calorie sweeteners. These may have different effects on body weight and health.
Second, some of the authors have ties to companies that produce low-calorie sweeteners, potentially creating a conflict of interest.
Summary and Real-Life Application
The majority of the evidence shows that using low-calorie sweeteners instead of sugar is beneficial, or at least neutral, when it comes to weight.
Another recent meta-analysis reached a similar conclusion (48).
If you prefer to sweeten your food, replacing sugar with low-calorie sweeteners may be an effective weight loss strategy, when combined with other lifestyle changes.