Coke vs. Diet Coke vs. Milk - The "Unhealthy Beverage Shoot-Out": Milk Reduces, Coke Increases Visceral Fat. Dreaded Diet Coke on Par With Plain Water

Image 1: I guess plastic dolls don't care about "fat" anyway.. so why would they drink diet coke, then?
I assume that at least some of you have read the Ask Dr. Andro post from August, 21, 2010, "Are Colostrum and Milk Products Healthy Muscle Builders, a Waste of Money or Toxic Waste?" As the title already suggests, the focus of this article was on milk / milk products as muscle builders and before I came across a recent study that was conducted by a group of scientists from Denmark, I would have called anyone who tells overweight persons to drink skimmed milk instead of water a total moron ... well, I guess, learning never stops ;-)

The VAT burning effects of skimmed milk

The Danish researchers conducted a randomized controlled trial to investigate the effects of different non-alcoholic beverages on the body composition of 60 healthy, non-diabetic subjects with a BMI (kg/m²) between 26 and 40 (age 20-50y). In the absence of any other dietary (or exercise) interventions, 45 of the subjects had consume 1l of either regular Coca Cola (yes it was the original ;-), diet Coke or Milk in addition to their regular water intake. The remaining 15 subjects who consumed nothing but water served as a control.
Figure 1: Macronutrient (g/100ml) and energy content (kj/day) of the three non-water beverages in the study (data adapted from Maersk. 2011)
If you look at the macronutrient composition (I know it is a joke to talk about a "composition" in the case of coke and diet coke ;-), it appears be quite obvious that neither of the two "high caloric beverages" would be particularly helpful in losing weight... so that this would leave us with the question, whether diet coke is - as many people claim - more fattening than water.
Figure 2: Changes in fat mass of subjects who consumed diet coke, milk or water over the course of the 6 months trial expressed relative to subjects in the regular coke group; * p < 0.05 (calculated based on Maersk. 2011)
If we take a closer look at the real effect of the different beverages, we will yet have to admit that we may have jumped to conclusion, here. After all, milk not water or diet coke was the only beverage the consumption of which lead to statistically significant reductions in the size of the unhealthy visceral fat in the 15 subjects of the respective arm of the trial. And of the three "coke replacements" that were tested, it was also the one that induced the most profound reductions in liver fat.
Figure 3: Changes in body weight, total fat mass, subcutaneous abdominal adipose tissue (SAAT), visceral fat to SAAT ratio, lean mass and bone mass after 6 months (data adapted from Maersk. 2011)
If we now take a look at the overall effects on body composition and bone mass, it does yet become clear that the often touted general weight-loss effects of low-fat dairy consumption are not supported by the data, as there were no "statistical significant differences" in either total body, or total fat weight between the groups. If we do yet discard the statistical shenanigan and use eyes instead of our calculators, I would say that there is a certain pattern, which - aside from the VAT burning effects of skimmed milk - fits very well, with what we did expect: Regular Coke is fattening, especially in the ectopic visceral fat depots, water is the best option for overall fat loss and milk has the advantage of helping with the retention or even the accrual of lean muscle and bone mass.

"And what about diet coke? Is it really benign?"

I know that this question is preying on your minds, right now: "Could it really be that the aspartame sweetened poison is not fattening? I mean doesn't it spike insulin?" ... based on the body composition data, the answer would be "Yes! 1l of aspartame sweetened diet coke per day does not hinder weight loss." If we do yet also consider a few other variables and - once again - don't rely all too much on the power of statistics, it does appear as if there exists the remote possibility that the difference between diet coke and water is more profound than the 15kj energy difference would suggest.
Figure 4: Changes in markers of blood glucose management and blood pressure after 6 months (data adapted from Maersk. 2011)
While none of the blood sugar related effects you see in figure 4 reached statistical significance, the group averages would suggest that drinking diet coke is associated with a reduction in blood glucose, basal insulin levels, no increase in HOMA-IR - all markers of improved blood sugar management. Moreover, the blood pressure of the diet coke consumers decreased to a similar and statistically significant (compared to regular coke) extent as the blood pressure of the subjects who consumed skimmed milk.
Figure 5: Changes in leptin, total cholesterol, triglycerides and HDL after 6 months (data adapted from Maersk. 2011)
A similar picture emerges if we take a final look at the lipid panels of the subjects, though only the changes in total cholesterol and triglycerides reached statistical significance (for diet coke, milk, and water compared to regular coke), it does nevertheless go against the vilification of diet coke that the diet coke consumers were the only ones, where the leptin levels decreased, had the greatest decrease in total cholesterol (which also explains that they had the lowest increase in HDL) and a similar profound reduction in triglycerides as the water consumers.

"So diet coke is better than water?"

Before you do now start to pound liter after liter of diet coke every day, let me put out one, or rather two hypothesis that could well explain the previously mentioned differences:
  1. Although the the lifestyle changes of the subjects regarding diet and physical activity were monitored at baseline, after 3 mo, and at the end of the intervention with the use of a 7 - d dietary record and a validated questionnaire concerning physical activity at work, during leisure time, and during sports, this was no clinical setting, where the scientists fed identical diets (except for the beverages) to every participant. The subjects in the diet coke group could have thusly simply have satisfied their sweet tooth by consuming the brown brew and could consequently have reduced their intake of sugary foods. That alone could explain the mostly statistically non-significant differences between the diet coke and the
  2. The "no-calorie" issue aside, diet coke is also caffeinated and as a regular visitor of this blog you will be well aware of the beneficial metabolic effects of caffeine. And though the 1L of coke contain only 131mg of caffeine, this would probably go as a "statistical significant difference" compared to water - and I guess I do not have to repeat that the latter was not the case for the previously discussed "advantages".
In view of the fact that this study is not suitable to answer the question whether diet coke or similar artificially sweetened beverages would hamper weight loss or induce weight gain in subjects on absolute identical diets, it goes to show that a) 1L of coke light is way better than 1L of real coke and that b) the consumption of 1L of skimmed milk exerts an unexpected beneficial effect on visceral adipose tissue - and that in the absence of any other dietary intervention... that does now make me wonder what the results would have looked like if the milk had not been skimmed, but full-fat, but I guess it will still take a few years until the paradigms have shifted and we will eventually see scientists hypothesize that full-fat or even raw milk could in fact be healthy ;-)
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