A Trial of Sugar-free or Sugar-sweetened Beverages and Body Weight in Children

Janne C. de Ruyter, Margreet R. Olthof, Jacob C. Seidell, and Martijn B. Katan

NEJM September 21, 2012

Full Text: http://www.nejm.org/doi/pdf/10.1056/NEJMoa1203034

Background

The consumption of beverages that contain sugar is associated with overweight, possibly because liquid sugars do not lead to a sense of satiety, so the consumption of other foods in not reduced. However, data are lacking to show that the replacement of sugar-containing beverages with noncaloric beverages diminishes weight gain.

Methods

We conducted an 18-month trial involving 641 primarily normal-weight children from 4 years 10 months to 11 years 11 months of age. Participants were randomly assigned to receive 250ml (8oz.) per day of sugar-free, artificially sweetened beverage (sugar-free group) or a similar sugar-containing beverage that provided 104kcal (sugar group). Beverages were distributed through schools. At 18 months, 26% of the children had stopped consuming the beverages; the data from children who did not complete the study were imputed.

Results

The z score for the body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) increased on average by 0.02 SD units in the sugar-free group and by 0.15 SD units in the sugar group; the 95% confidence interval (CI) of the difference was -0.21 to -0.05. Weight increased 6.35kg in the sugar-free group as compared with 7.37kg in the sugar group (95% CI for the difference -1.54 to -0.48). The skin-fold thickness measurements, waist-to-height ratio, and fat mass also increased significantly less in the sugar-free group. Adverse events were minor. When we combined measurements at 18 months in 136 children who had discontinued the study with those in the 477 who completed the study, the BMI z score increased by 0.06 SD units in the sugar-free group and 0.12 SD units in the sugar group (P=0.06).

Conclusions

Masked replacement of sugar-containing beverages with noncaloric beverages reduced weight gain and fat accumulation in normal-weight children.

Opening comments

Today’s article has a high likelihood of being taken way out of context – something that is not allowed here. Some may argue that this article tries to answer one of the most pressing questions of the 21^st century, and that is, “what is the cause of childhood obesity?” However, this article does not due certain methodological weaknesses leaving us wanting for more. Instead, the article shows us exactly what we’ve known all along, and that is, when you eat fewer calories, you gain either less weight or no weight at all. In today’s article, we’re talking about the former. So without further ado, I will show you why this article doesn’t prove that sodas cause obesity before it gets taken way out of context on every news channel around… because it most certainly will.

Introduction & Results

The article begins with acknowledging the concomitant rise in both sugary beverage consumption and obesity in children. The authors postulate this correlation is due to soda’s inability to compensate for calories at subsequent meals – a topic I covered thoroughly back in April. Indeed, the literature to-date suggests that liquid calories do not have the same effect on satiety that solid foods do. Therefore, sodas may promote increased food intake (or lack of calorie displacement) by virtue of sugar’s vehicle (liquid medium) rather than the sugar itself. However, none of this was evaluated in today’s study.

Lastly, the authors note the lack of convincing evidence suggesting sodas’ causational role in obesity due to other collinear factors such as fast food consumption (which usually coincides with soda consumption) and lack of physical activity (or as they put it, increased television watching). Therefore, they sought to examine the effect of replacing soda with a masked, calorie-free soda substitute on weight gain (further adding to the lack of causational data).

In the end, both groups (those who drank the sugar-sweetened soda and those who drank the diet soda) gained weight and fat mass (as expected given their age). However, the group receiving the sugar-sweetened soda gained more weight (16lbs vs. 14lbs) and more fat mass than the sugar-free group (3.5lbs vs. 2.3lbs).

Study Strengths

Strengths of the study include double-blind randomization of participants, an 18 month study duration, large sample size (n = 477), and urinary sucralose measures to assess the sugar-free group’s adherence to the intervention. Other strengths include custom-made sodas which were designed to taste identical (this eliminates subject bias) and teachers’ reminders and physical watching of the children consuming the beverages in school (ensures adherence).

Study Weaknesses

Unfortunately, the study is filled with more weaknesses than strengths. First and foremost, there was no mention of diet or physical activity of any of the 477 participants who completed the study. Secondly, 26% of participants dropped out for unspecified reasons. Thirdly, skinfold measurements and BIA were used to assess body composition, both of which are highly prone to human error. Now don’t get me wrong, I am not naïve enough to think that all 477 kids could have been DXA’d. However, a subset of participants could have been analyzed using DXA to confirm skinfold and BIA measurements. Lastly and most importantly, assuming that the two groups’ diets were identical at baseline, the addition – or in this case the subtraction – of one soda per day (104 kcal) for 18 months resulted in the sugar group potentially receiving over 56,000 kcals MORE than the sugar-free group. All this proves is that if you consume more calories, you gain more weight. WOW, huge shocker there!

Comments and conclusions

It’s not surprising that the sugar-free group gained less weight than their sugary counterparts; the researchers theoretically removed over 56,000 calories from the sugar-free group’s diet over an 18 month period! Furthermore, suspicions of increased food intake caused by soda intake were never even evaluated. In order for that to happen there needed to be some form of assessment of diet over the 18 month period. This, however, was mistakenly left out. On the bright side, this study does lend some credence to efforts to reduce soda intake in children, despite showing no causational effects of soda on obesity whatsoever. Remember, sodas are an easy and readily available source of nutrient-poor calories; that is all. Sodas don’t cause obesity more so than does an extra equi-caloric serving of brown rice each day. If you want to enjoy that can of soda you have to remember to eat less of other things throughout the day (whether or not this is possible in free-living populations is the TRUE question and one that was nowhere close to being answered in this study). Therefore, although the aim was to examine the effects of replacing a chronically consumed sugar-sweetened soda with a diet alternative on weight gain, I would suspect similar findings with ANY food source being substituted with a calorie-free alternative.

Bottom-line: consume fewer calories; you’ll gain less weight if you do.