People who drink sugar-sweetened beverages tend to gain more weight over time.
However, it is not known whether all types of sugar are equally fattening.
For this reason, a team of scientists recently examined how different forms of sugar affect calorie intake.
Here is a detailed summary of their results, published in the American Journal of Clinical Nutrition.
Sugar-sweetened beverages are a major source of calories in Western society (1).
Studies suggest that drinking sugar-sweetened beverages promotes excessive calorie intake, weight gain and obesity (2).
Several factors could explain this:
- Liquid calories bypass the body’s appetite-regulating system. They are simply added on top of normal calorie intake (3, 4, 5, 6).
- Fructose doesn’t stimulate insulin release when ingested. For this reason, it may not suppress appetite as strongly as glucose (7).
However, exactly how or why this happens is not fully understood, and further studies are needed.
Scientists from Seattle examined the effects of fructose-sweetened beverages on calorie intake, and compared it with beverages sweetened with glucose, high-fructose corn syrup or aspartame.
Basic Study Design
This study was based on the secondary analysis of two randomized, controlled crossover trials.
The main purpose of this study was to examine the effects of fructose-sweetened beverages on calorie intake, and to compare it with glucose, high-fructose corn syrup (trial B) or aspartame-sweetened beverages (trial A).
A total of 9 healthy, normal-weight adults participated in this trial. They were randomly assigned to one of three groups:
- Fructose: For 8 days, the participants consumed 4 servings of a fructose-sweetened beverage every day.
- Glucose: During the same period, the participants consumed 4 servings of a drink sweetened with glucose. A small amount of aspartame was also added to match the sweetness of the fructose.
- Aspartame: In this control group, the participants consumed 4 servings of aspartame-sweetened beverages per day.
The amount of glucose and fructose consumed daily was equivalent to 25% of each subject’s estimated calorie requirement. Conversely, the aspartame-sweetened drink provided only 4% of their estimated calorie needs.
The study had a crossover design, which means that all participants were in each of the three groups on different weeks, separated by 20 days.
All participants spent 8 days in each group, during which the study kitchen provided them with standardized food, or an amount equivalent to 125% of their estimated calorie requirements.
A total of 24 healthy adults completed this trial. Half of them were overweight or obese, whereas the rest were normal-weight.
They were randomly assigned to one of three groups:
- Fructose: For 8 days, the participants consumed beverages sweetened with fructose. As in trial A, the daily amount was divided between 4 servings.
- Glucose: Participants in this group consumed fructose-sweetened beverages instead of glucose. A small amount of aspartame was added to make the sweetness equal to that of the fructose beverage.
- High-fructose corn syrup: In this group, the participants got beverages sweetened with high-fructose corn syrup, which is essentially a mixture of fructose and glucose. A small amount of aspartame was also added.
Otherwise, trial B was identical to trial A.
Bottom Line: This study used data from two small randomized controlled trials examining the effects of fructose on calorie intake, and comparing it with glucose, high-fructose corn syrup or aspartame.
Finding 1: Sugar-Sweetened Beverages Increased Calorie Intake
In trial A, calorie intake was significantly higher among those who got 25% of their estimated calorie needs from sugar-sweetened beverages, compared to those who got aspartame.
Glucose- and fructose-sweetened beverages increased calorie intake equally.
The chart below shows the differences in calorie intake between groups, presented as the percent of estimated calorie requirement:
In the present study, body weight did not change significantly between groups. This is probably explained by the low statistical power of the study, and its short duration.
Bottom Line: Sugar-sweetened beverages increase calorie intake, compared to beverages sweetened with aspartame. For this reason, they may promote long-term weight gain.
Finding 2: Fructose and Glucose Increased Calorie Intake Equally
Fructose, glucose and high-fructose corn syrup all had similar effects on calorie intake. Also, no differences were detected when the participants were divided into subgroups based on gender or body weight.
The chart below shows the differences in calorie intake between groups in trial B, presented as the percent of estimated calorie requirement.
Bottom Line: Fructose, glucose and high-fructose corn syrup increased calorie intake to the same extent. Put simply, liquid sugar promotes weight gain, regardless of the type of sugar.
The study was well planned and executed. However, it had several limitations.
First, both trials recruited a small number of participants, especially trial A, which included only 9 participants. This limited the statistical power, and means that smaller but significant findings may have been missed.
However, trial B included a greater number of participants than trial A, and was based on proper sample-size calculations.
Second, both trials were intentionally of short duration to prevent adverse health effects, such as weight gain. But this means that the results may not necessarily be generalized to longer periods.
Additionally, in trial A, the participants in the fructose and glucose groups were provided with more calories, or a total of 150% of their calorie requirements, compared to those in the aspartame group, which received only 129%.
This difference might have contributed to the differences in calorie intake between groups.
Finally, the participants were provided with a standardized diet that did not include snack foods high in sugar and fat. This limits the generalizability of the results further.
Bottom Line: The study was well planned and implemented. However, it had a few shortfalls that might have affected the results and limited the generalizability of the results.
Summary and Real-Life Application
In short, consuming sugar-sweetened beverages leads to a higher calorie intake, compared to aspartame-sweetened beverages.
Fructose, glucose and high-fructose corn syrup all had a similar effect. This indicates that liquid sugar increases calorie intake, regardless of the type of sugar.
Simply put, if you care about your weight, you should avoid sugar-sweetened beverages.