Soda vs. childhood obesity

What happens if you give skinny kids a can of fully sugared regular soda to drink every day for a year?

What happens if you take the soda away from overweight kids for a year?

The answer to these two questions should be a definitive user’s guide to the question: how bad is soda for my children?   And we got those answers this week.


A set of powerful studies were recently published, the likes of which I thought we’d never see.  It’s unethical to assign anyone to start smoking so we can properly study the effects of cigarettes; and before today, I would’ve thought it unethical to assign young children to start drinking fully sugared regular soda.  And not just one or two cans…  over 350.  For the 4 year olds the first study, by the end of the trial they had been on soda for almost a third of their life… during a critical period of development.  Ethics schmethics.  Hopefully this study will never be repeated.

Exhibit A.  A trial of sugar-free or sugar-sweetened beverages and body weight in children (Ruyter et al., 2012)

The DRINK study (Double-blind, Randomized Intervention study in Kids).

Speaking of ethics, I have a disclosure to disclose: this study was a bad idea.  The researchers and parents who volunteered their children are either non-readers, or non-believers of The poor, misunderstood calorie.  And this is probably the only time I’ll ever say it was better that this study wasn’t a crossover; that way, at least half of the kids weren’t chronically exposed to soda .

Amsterdam, the Netherlands.  18-months; 477 healthy children aged 4 – 10 years old.  Regular vs. diet soda;  26 grams of sucrose vs. 34 mg sucralose & 12 mg of acesulfame K.  They had to have a custom soda made because Coca-Cola and/or Pepsi would’ve squashed Ruyter like a fly if her results showed any negative effects.  With no further ado:


In contrast to what we usually discuss (i.e., weight loss), this is a study of growing children.  Accordingly, they all gained weight.  Those on regular soda got 25% heavier while those on diet soda by 21%.  But [as predicted], there’s a dark side to this story.

No, not that Dark Side,

that one.

Regular soda drinkers gained 55% more fat than diet soda drinkers.  Being accustomed to seeing much smaller differences between groups, I usually quip something like: “obesity doesn’t happen overnight.”  But not in this case.  That is a drastic difference.  Childhood obesity epidemic, anyone?

Some people argue that when someone switches from regular to diet soda, they just make up the calories elsewhere.  IT DOESN’T MATTER; any other calories are less fattening than soda.  All calories are not created equal.  N.B. This study did not suffer from the usual flaws like small sample size or short study duration.

Exhibit B.  A randomized trial of sugar-sweetened beverages and adolescent body weight (Ebbeling et al., 2012)

The opposite study.

Boston,  Massachusetts.  1 year intervention + 1 year follow-up; 224 overweight/obese children aged 14 – 15 years old.  The experimental group received a “multicomponent intervention designed to reduce the consumption of sugar-sweetened beverages.”


Those in the control group gained 9 pounds, or ~5% of their starting body weight, while those who reduced soda intake only gained 4 pounds (less than half).  Both groups reduced sugar intake, by 36 grams and 76 grams in the control and experimental groups, respectively, but soda drinkers gained over two times more fat.  TWO TIMES =  DOUBLE.

During the year following the study’s conclusion, the experimental group started drinking more sugar and the difference in body weight between the groups got smaller, confirming the specificity of the intervention.

Summary:  Ruyter’s study in healthy Dutch children: drinking more soda increases fat mass.

Ebbeling’s study in overweight/obese American adolescents: drinking less soda decreases fat mass.

These studies are randomized intervention trials, not simply observational, cross-sectional, or otherwise epidemiological studies.  They are designed to demonstrate cause and effect, not just correlations or random associations.

these findings shouldn’t be surprising (to regular readers of TPMC)…

Fructose vs. leptin, et al. (April 21, 2011): fructose causes leptin resistance (obesity), which is reversed by a sugar-free diet.  [sugar = sucrose = fructose + glucose]

Sugar vs. fat (April 27, 2011): sugar makes fat bad for you.

Fructose vs. The Laws of Energy Balance (December 13, 2011): fructose causes metabolic derangements and visceral fat accumulation.

sucrose, visceral fat, et al. (January 3, 2012): regular soda, but not milk, diet soda, or water increases visceral fat; and fructose is worse than glucose.

Conclusion:  Drinking regular soda may not be as dangerous as playing in traffic, but it can make you fatter.

calories proper

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  • Pat D

    Great article. Are there any studies that gave the subjects an extra 26 kcal from fat in one group and sugar in the other? That would truly identify your calorie vs. calorie.
    As a soon to be parent, I enjoyed the content you have written here.

    • William Lagakos

      Yes, there have even been isocaloric substitutions of glucose vs.
      fructose. They all point to the same
      thing: junk food is bad for you, and the junkier it is (e.g., fructose compared
      to glucose, or trans fats compared to regular fats), the worse it is.

      • Dylan Klein

        At what doses? I’m not sold on the entire fructose is evil debate. All of the evidence pointing to fructose being evil has to do with irrelevant dosing of free fructose. Sure, 100g of fuctose may be harmful. But that means you have to consume 200g of sucrose. Anyone consuming that much sugar probably isn’t engaging in the most healthly behavior to begin with. Fructose is almost never consumed without near-equal amounts of glucose (unless you’re guzzling agave nectar), so is must be taken in the context with normal human consumption patterns.

        • William Lagakos

          On one hand, I agree, the doses used in randomized intervention [good] studies range from high to too high. But given the costs of such studies, they need to use high doses because the studies are too expensive to run long enough to see an effect with lower doses, and the cheaper epidemiological studies don’t really tell us anything. That’s just the nature of the beast. On the other hand, de Ruyter’s kids got fatter on half a can of soda.

  • Dylan Klein

    Should we really be THAT surprised. They theoretically removed over 56,000kcals from the sugar-free group over an 18 month period. All this shows us is that if you eat fewer calories, you gain less weight.

    And in regards to the ethics of the study, the kids had to already have been habitual drinkers of soda (which says a lot about parenting for the 4 year olds). The study wasn’t giving sodas to non-drinkers.

    At the end of the day, sodas are a readily available and easily consumable source of nutrient-poor calories; that is all.

    • William Lagakos

      Good points, Dylan. I was
      surprised Ebbeling’s kids didn’t compensate for the missing sugar calories… they
      actually ate even less (sugar calories declined by 304 while total calories
      declined by 454). It gives a whole new
      meaning to “empty calories.”

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  • Guido Vogel

    How did you calculate the 55% body fat difference in the first study? I could find:

    “Children in the sugar-free group who completed the study gained 35% less body fat than those in the sugar group, according to impedance measurements,26 and 19% less when fat mass was calculated from the sum of the thicknesses of four skinfolds. “

    • William Lagakos

      fat mass increased by 19% in the diet soda drinkers and by 29% for regular. 29 is ~55% greater than 19%…

      19 * 1.55 = 29