Monday, November 18, 2013

Sugar Sweetened Beverages & Total Energy Intake: Studies Suggest That Normal-, Overweight & Obese Women CAN Compensate for 168 Additional Sugar Calories Per Day

Usually they are touted as the reason for weight gain: Sugar-containing soft drinks like the Scottish brew Irn Bru. In the study at hand, however, they helped 41 obese women lose weight - how come?
Despite the fact that it is not the first of it's kind, I decided that the paper Roy Nelson sent me the a couple of days ago may still be worth being covered in a brief article. Marie Reid and her colleagues were after all able to show that we can, theoretically and without conscious effort, compensate for the additional energy intake from sugar-sweetened beverages.

As I already mentioned, this is not the first study Reid and her colleagues from the Hull, Ulster and Herriot-Watt Universities in the UK conducted, but it is the first one where the subjects, obese women, with previous diet experience, came right from the subgroup of the population of whom we simply assume that their weight problems would (partly) result from these "empty calories".

Would the women "recognize" the 168kcal of pure sugar in their diets?

After exclusion and dropouts, Marie Reid et al. were left with a total of 41 healthy obese (BMI 30– 35 kg/m²) 20-50 year-old women who were randomly assigned to consume sucrose (n=20) or aspartame (n=21) drinks over 4 weeks in a parallel single-blind design.

Based on the previously mentioned experiments with normal- and overweight women, the researchers knew women with higher body weights had a harder time to compensate for the 168kcal the sugar-sweetened drinks delivered than their lean peers. It was thus interesting to see, whether the obese women (1) would compensate for the additional energy intake and (2) whether the compensation would be less pronounced than in the lean and overweight participants of the previous studies.
What's missing from the study at hand are the really important things, i.e. the changes in blood glucose and lipid metabolism and the differences in waist circumference and / or body fat levels. So whatever the scale of the subjects said, this and the previous studies by Reid et al. don't provide the basis for an acquittal of sugar sweetened beverages (learn more about the debate the role of Pepsi, Coke & Co in the diabesity epidemic).
Instead of simply having their subjects fill dietary records, the scientists used the weight response to judge, whether or not the women fully or partly compensated for the additional energy intake from the sugar sweetened beverages (note: the beverages contained regular sugar, no HFCS). Reid et al. did yet also analyze the changes in macronutrient composition to elucidate, whether the expected reduction in regular (food) energy intake would go at the expense of any particular macronutrient, i.e. carbs, proteins or fats.
Figure 1: Macronutrient and energy intake of the sugar (left) and aspartame (right) group (Reid. 2013)
The test drinks the scientists used came in 250 ml bottles. The women were instructed to consume four of these bottler, the content of which was sweetened with plain sucrose (fructose + glucose) or aspartame. Of the latter, the commercially available soft drinks (Irn Bru) contained
  • 10.5g of sucrose, but no aspartame in the regular and (sugar)
  • 0g of sucrose and a miniscule amount of aspartame in the diet variety (aspartame)
If you  do the math you can easily calculate that the regular Irn Bru provided an additional energy intake of 4x10.5g/day x 4kcal/g = 168kcal/day and a total of 4704kcal if we take the whole 4-week study period. According to the faulty rule of thumb that informs us that 1lbs of fat would equal 3,500kcal (learn why this is *bs*), the women in the "regular" Irn Bru group (sugar) should end up with "exactly" (*rofl*) 672g of additional fat on their hips.

Sugar doesn't make you fat and artificial sweeteners seem to hamper weight loss!?

I guess (or hope) that you will not really have expected to see those 672 extra grams of fat on the hips of Reid's, subjects at the end of the study. Still, most of you will probably have expected that the ladies did gain weight, right? Much to my own surprise, this was not the case: In fact, the vast majority of the ladies missed the predicted weight gain by more than 1kg (1.72 (SD 0.47) kg).
Figure 2: Illustration of the results of the study at hand (obese women) and previous studies with normal- and overweight women all of which showed sufficient energy compensation for the 4x250ml soft drinks  (Reid. 2007, 2010, 2013); note the listed "weight loss", e.g. -1.72kg, denotes the difference between the actual and the predicted body weight, see red box!
Now, being part of a study like this certainly is a confounding factor that could precipitate to conscious energy restriction. If this was the reason the ladies didn't gain weight, though, the women in the aspartame group would actually have had to lose a significant amount of weight.
It's not like the lean or overweight  women did not gain any weight at all.
This is not "sugar induced weight loss"! If you look at the graphs from the previous studies (left) in which Reid et al. did not use the "compared to expected weight gain" trick, it's obvious that only the lean women got away without weight gain.  In the overweight and obese women, there was a small, but due to the large outliers statistically non-significant increase in body weight.
I mean, you would certainly expect the women in the placebo group to take the same measure to make sure the potentially sugary (remember this is a randomized, blinded study) brew they were drinking would not end up on their hips.

A brief glance at the total energy intake in Figure 1 appears to confirm that: The women in the aspartame group did also reduce their energy intake. Due to significant differences among the study participants this did however not lead to a net change in body weight. From a statistical perspective, this means that the body weight of "Mrs. Average" did not change - neither in response to the sugar- nor in the aspartame sweetened drinks. 
Wtf? Sugar does not make you fat!? There are a couple of good reasons we got to be cautious with generalizing assessments like "sugary drinks are not the problem!":
  1. In contrast to the study Sartor et al. found that their participants gained 1kg of fat in only four weeks "on" Lucozade energy drinks | more
    Neither this study nor the previous studies measured the health-relevant changes in body composition of which the 2012 study by Sartor et al. clearly shows that they will occur if you simply add a bunch of sugary energy drinks to your diet (learn more).
  2. With its 100% plain sugar content, the beverage the scientists used is not representative of the "average" soda. It is thus unwarranted to conclude that the lean, overweight and, in the study at hand, obese subjects would also be able to compensate for beverages with HFCS, dextrose or whatever other funky caloric sweeteners the industry uses.
Even if (2) was not true and similar compensatory effects wouldn't be observed with sweeteners, the data from the study at hand clearly weakens the "empty calories" argument. It does so, however, without being the first class acquittal Sugar Nutrition UK was probably hoping for when they decided to provide the financial means for this study.
  • Reid M, Hammersley R, Hill AJ, Skidmore P. Long-term dietary compensation for added sugar: effects of supplementary sucrose drinks over a 4-week period. Br J Nutr. 2007 Jan;97(1):193-203.
  • Reid M, Hammersley R, Duffy M. Effects of sucrose drinks on macronutrient intake, body weight, and mood state in overweight women over 4 weeks. Appetite. 2010 Aug;55(1):130-6.
  • Reid M, Hammersley R, Duffy M, Ballantyne C. Effects on obese women of the sugar sucrose added to the diet over 28 d: a quasi-randomised, single-blind, controlled trial. Br J Nutr. 2013 Oct 29:1-8. [Epub ahead of print]