Friday, December 20, 2013

Minimal Carb Reduction, Maximal Results? Study Compares 60% vs. 40% CHO Diets + 6-Week 25% Energy Reduction

Does "moderate low carb" work? And if so how much of the usual triglyceride and glucose lowering benefits of walking the whole nine yard are you going to miss?
I know that 40% carbs is not what you consider "moderate", but for most of our fellow countrymen and women, cutting back on at least one serving of their beloved pasta and bread is already more than you can ask for if you want a compliance that's beyond 1%. Against that background it is all the more important to know whether even small changes in the overall carbohydrate intake have to offer obviously less pronounced, but still significantly beneficial health benefits to overweight and obese individuals -- small changes like the 20% reduction in carbohydrate intake in the "moderately-restricted carbohydrate diet" (MRCD) arm of the most recent study from the Isfahan University of Medical Sciences in Teheran, Iran (Rajaie. 2014), for example.

1/2 low carb = 100% adherence, but at which costs?

The experiment was conducted by Somayeh Rajaie and colleagues. The results will be published in the January 2014 edition of the peer-reviewed scientific journal Nutrition. Results of which the authors say that they are particularly relevant, because...
"[...e]arlier studies on the management of metabolic syndrome (MetS) have mostly focused on very low carbohydrate diets" whereas long-term adherence to such diets is difficult for apparently healthy people."(Rajaie. 2014)
I can already hear the first people arguing that this was bullshit. What is bullshit, though, is to close your eyes and ignore the real world problems people encounter, when they go from years of sugar, sugar, sugar, sugar and fat to diet that have almost no sugar in them. I mean, come on low carb boys and girls, ask your non-fitness-infected friends about going without pasta and pizza for the rest of their lives. What are these people going to answer? ... You see: long-term adherence to very-low-carb diets is difficult for the average "apparently healthy people", the Iranian scientists are talking about, here ;-)
Figure 1: Number of servings from different food groups (left) and macronutrient composition (right) of the basleine diet of the 39 overweight study participants (Rajaie. 2014)
While it may not be as straight forward as it is with rodent studies, we still have to take into account that the baseline diet could render the significance of the data from a human study similarly questionable as that from rodent studies. Figure 1 does yet tell you that these aforementioned "average apparently healthy" man or woman in Iran eats pretty much the same sh*t as his / her American or European counterparts: a diet that's a "perfect" mixture of fats and sugar that will blow you up much more effectively than a really high carbohydrate + low fat, or a really low carbohydrate + high fat diet.

Apropos "high carbohydrate": The basline carbohydrate intake is actually so "low", that the subjects in the high carbohydrate group of the study at hand had to increase their carbohydrate intake to get it up to the recommended 60% of their total energy intake. By implication, this means that the subjects in the "moderately restricted carbohydrate" group didn't reduce their carbohydrate intake by 20% (as the abstract appears to imply), but only by 10% vs. baseline.

Adding or subtracting 10% carbs - what's better when you're dieting?

Ok, enough of the number games. Basically what I am trying to say was that the effective reduction in carbohydrate intake during the 6-week intervention period is only 10% - not 20%, as the difference between the high carbohydrate and the "moderately restricted" carbohydrate group (MRC) would suggest.
Figure 2: Macronutrient composition of the diets during the 6-week intervention (left) and changes in macrontrient composition (right) expressed relative to baseline (Rajaie. 2014)
As I already pointed out, this implies that the high carbohydrate group effectively increased their relative carbohydrate intake (see Figure 2, right). In contrast to what the increasing number of carbophobs out there would probably have expected, this outrageous increase in carbohydrate intake did not result in weight or fat gain.

Small changes make a difference! But that's small changes in energy, not carbohydrate intake

As the data in Figure 3 goes to show you, both groups lost almost exactly the same amount of body weight (1.72kg HC vs. 1.70kg MRC), they also gained the same ~800g of lean mass and lost 1.3kg of body fat.
Figure 3: Changes in body weight, BMI and body composition after 6 weeks (Rajiae. 2014)
In other words: From a body composition perspective the 20% difference in carbohydrate intake obviously didn't make a difference - and the "trend toward greater reduction in waist" in the MRC group, the authors highlight in their abstract could be mediated by the baseline difference (1 cm larger waists in the MRC group).

A very similar image emerges for the often advertised beneficial effects "real" low carb diets have on the serum triglyceride (TG) levels. In the "moderately restricted carbohydrate" group, they were simply not there. With a p-value of p = 0.07 for the inter-group difference, these changes were even more "random" than the previously cited effects on the waist line. And if the "greater reduction of systolic blood pressure (−8.93 versus −2.97 mm Hg; P = 0.06) and diastolic blood pressure (−12.7 versus −1.77 mm Hg; P = 0.001)" in the MRC group was not simply a result of a (in the long term) not necessarily beneficial reduction in the sympathetic tone is similarly difficult to tell.

Read: " Two Days A Week High Protein, Low Carb Fast Cuts >10% of Body Fat in 4 Months" | more
Bottom line: Hovering around in the "comfort zone" is not going to help you make huge changes. When you run a 25% energy restriction you will lose body weight. As the study at hand shows, even without sacrificing muscle tissue. Whether you do that with a 40% or 60% carbohydrate does not appear to matter for the average overweight individual.

Long story short, if you don't go to the extremes and adhere to a sane energy deficit (>20%, but <35%), it really doesn't matter whether you eat some more carbs or some more fats. And let's be honest, brutally honest: For an increasing part of the ever more obese inhabitants of the Western obesity belt, it would already be a remarkable achievement not to get fatter every day. If these people managed to lose ~1.3kg of pure fat while increasing their lean mass by almost 1kg that would be a major success.
Reference:
  • Rajaie, S., Azadbakht, L., Khazaei, M., Sherbafchi, M., & Esmaillzadeh, A. (2014). Moderate replacement of carbohydrates by dietary fats affects features of metabolic syndrome: A randomized crossover clinical trial. Nutrition, 30(1), 61-68.