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?|
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)|
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)|
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)|
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.
- 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.