Monday, December 19, 2011

The Fat Truth Behind the Dairy Weight Loss Miracle: MUFA and PUFA Impair, Saturated Fat and Plenty of Micronutrients Drive Full-Fat Dairy-Powered Fat Loss.

Image 1: Kids who drink more milk, tend to be leaner... and that despite (?) the fact that this stuff comes out of an animal and is full of bad cholesterol and fat - outrageous ;-)
Plenty of interesting news, lately, so this one - just like the recently released hypertrophy / hormone correlation study by Stuart Phillips, about which I have been talking in yesterday's installments of the Intermittent Thoughts got somewhat delayed. With the Christmas holidays and the approaching and all those New Year's weight loss resolutions (I would prefer the term "fat loss resolution", though ;-) already on your mind, I do yet think that it is about time to break the news on the "fat" reason for the purported beneficial effects an increased consumption of dairy products during periods of caloric restriction appears to have on weight and more specifically body fat loss (Linn. 2000; Peirara. 2002; Shahar. 2010).

Dairy, calcium or simply the right macronutrient composition?

The scientific results I am going to present are taken from a study that was published in the Journal of Nutrition and Metabolism a few weeks ago (Smilowitz. 2011). In a randomized, placebo-controlled study Jennifer T Smilowitz and her colleagues from the USDA-funded (keep that in mind, when interpreting the results, or rather the scientists interpretation of the latter ;-) Western Human Nutrition Research Center assigned their 62, against the background of the rampant obesity epidemic, only slightly overweight young subjects (mean age: 25y; BMI ~28) to a calorically restricted diet (-500kcal) that was specifically designed to "provide comparable levels of macronutrient and fiber, to approximate the average consumption in the US" (35% fat, 49% carbohydrate, 16% protein and 2-3g fiber), which contained either
  • 0-1 servings of dairy, with 500mg dietary calcium (from the whole diet) + placebo,
  • no dairy (still 500mg calcium from diet), 900mg of supplemental calcium carbonate, or
  • 3 servings of dairy, with 1400mg of dietary calcium (from the whole diet) + placebo
Thusly, the study basically mimicked, what would happen if you told the average American to just keep their usual sedentary life-style (the subjects were instructed not to start to exercise or anything like that) and either just reduce his caloric intake by 500kcal, to do the former and to make sure to have three servings of dairy per day, or to just take an additional "healthy" calcium carbonate supplement.

Eat dairy + whatever you want and lose weight?

Now, interestingly, the subjects were not only free to chose whether they wanted to consume the dairy from low or normal fat cheese, milk and/or yoghurt, they were also relatively free as far as the rest of their dietary choices were concerned so that the detailed analysis of their food-logs allowed for conclusions to be drawn that went beyond the initial scope of the study... but let's take one thing after the other.
Figure 1: Dietary intake (macronutrients in kcal/day) of the subjects before and at the end of the 12-week study period and relative changes in carbohydrate, protein and fat intake (data calculated based on Smilowitz. 2011)
If you take closer look at the analysis of the dietary records the subjects had to keep, you will notice that the minor differences in the dietary prescriptions induced quite profound changes as far as the macronutrient composition of the respective diets was concerned. While the subjects in the non-dairy groups, regardless of whether they received a calcium supplement or placebo, cut back on all the three major macronutrients, the requirement to incorparate three servings of dairy into their meal-plan, alone appeared to suffice to keep the protein intake of the dairy group at a reasonably high level (~72g; which would be 0.96g/kg body weight). The protein intake of the two non-dairy groups, on the other hand dropped to 57g (0.75g/kg) and 54g (0.7g/kg) for the calcium and placebo supplemented groups, respectively.
Figure 2: Changes in body composition and measures of insulin sensitivity after 12-weeks on the high dairy, calcium supplemented or placebo supplemented diets (data calculated based on Smilowitz. 2011)
In view of the facts that the subjects had to stick to the calorically restricted diet for 12 weeks, it should not surprise you that all of them lost a statistically significant amount of body weight (cf. figure 1) and improved their insulin sensitivity (as indicated by reduced insulin levels and HOMA-IR values).What should yet strike your eye are the increased reductions in body fat and waist circumference and the greater increase in lean mass-% in the high dairy group. Now, you will probably assume that this was a result of the higher protein intake, and that may in fact have been the case, as one of my beloved model calculations by which scientists "adjust" their data for whatever they want (usually until the result is in accordance with their hypothesis ;-) revealed that
Dairy product consumption was found to be significantly associated with reduced WC [waist circumference] and %BF [percent body fat], however, these relationships were no longer significant after adjustment [my emphasis ;-] for protein and energy intake and physical activity.
Figure 3: Scatterplot of the partial correlations between reported 12-week mean dietary fat intake expressed as % of total energy and changes in lean body mass (LM) and body fat % (taken directly from Smilowitz. 2011)
Assuming that this "adjustment" yielded valid results it is all the more interesting what a subsequent analysis of the "adjusted" data revealed:
When expressed as a percent of total energy, dietary fat composition was correlated with changes in anthropometrics. Reported MUFA at 12 wk was inversely and positively associated with changes in % LM and % BF, respectively.
Or, in the words of the layman: The greater the relative monounsaturated fatty acid (MUFA) content of the subjects' diets, the more lean mass was lost and the more body fat was retained during the study period (cf. figure 3). Similarly, a higher intake of polyunsaturated fatty acids (PUFA) was associated with lower reductions in waist circumference, and while  the scientists claim that the n3:n6 ratio did not matter, it should make you wonder if it could actually be coincidental that the n6:n3 ratio in the dairy group was 6.6, while the ones in the calcium and placebo groups were 8.7 and 7.9, respectively.

And what about saturated fats? 

Moreover, the USDA scientists mention only "in the small print" that most fundamental (and statistically significant) distinguishing feature of the dairy group, who unquestionably had more favorable weight loss results despite an overall greater caloric intake, was (and I am quoting this from the paper) "a significantly higher intake of SFA [saturated fats] and lower intakes of MUFA and PUFA compared with the calcium supplement and placebo groups". Now, guess where this "bad" saturated fat came from? Well, probably from full-fat dairy! And guess why those "good" MUFAs and PUFAs were missing from the diets of the high dairy group. Well, probably because the subjects ate less "healthy vegetable oils"... ah, and did I already mention that the dairy group also ingested disproportionally (relative to their caloric intake) higher amounts of biotin, vitamin B12, vitamin D and - God forbid! - cholesterol?
Image 2: Even if you like animals, eating their eggs and full-fat dairy products won't hurt them.

So, while the scientists do their best to conceal that all those "bad things", like a high protein intake and nutrient dense real non-processed animal products with their original (saturated) fat, cholesterol and micronutrient content left untouched, are the true driving forces of successful weight loss (and, you bet, also maintenance), I am quite confident that you, as a diligent student of the SuppVersity, would not have needed the doctored... ah, pardon me, ... I obviously meant the well-adjusted results of this study to know that. After all, you are probably just enjoying a rib-eye steak with some delicious melted butter from grass-fed cows, right?