|Too little leucine & phenylalanine in O.'s diet?|
A recent study from the University of Sao Paulo does now provide some insights into the important role the high amount of essential amino acids (leucine and phenylalanine, to be precise) in the typical bodybuilding diets may play with respect to its moderating effects on the lean muscle loss and body fat gains of Opra-esque ups and downs in body weight.
Leucine + Phenylalanine + diet and refeed = ???
I guess the details in the headline to this paragraph are not actually detailed enough to get an idea of what Donato Jr. et al did in their latest rodent study, are they? I see. I will still try to stick to the most important facts.
|Contrary to the beliefs of many mostly female victims of life-long dieting, never eating to satiety is NOT going to promote a bikini body - quite the contrary (learn more)|
- 8.55g of casein (control), or
- 5.45g l-leucine + 3.1g l-phenylalanine (LP)
I guess by now you may be asking yourself about the connection to Oprah and boydbuilding diets, right? Well, the 28-day experiment actually had 2 phases a dieting and a maintenance phase. Both cycles were 14 days long. In the first one, the rodents dietary intake was cut in half, while they were allowed to eat as much as they wanted (ad-libitum feeding) in the second 14-day cycle.
YoYo or not - is that the question?
Now, what would you guess happened? I mean, remember: Both diets had an absolutely identical amount of calories and protein - so, the rodents in both groups "hit their macros", right? The logical answer - at least to an increasingly popular, but over-simplistic dietary paradigm - must be: "Nothing! Both groups will end up at an identical body composition.", right!? A brief glance at the data in figure 1 does however suffice to tell you the IIFYM prognosis was not exactly correct - at least not if we take the changes in body composition into account.
|Figure 1: Effects of weight cycling with casein (control) and leucine + phenylalanine (L+P) on body composition (left), feed efficiency (=how much weight do you gain per gram of food) and weight (Donato Jr. 2013)|
Leucine + phenylalanine also blunt the reduction of T4 → T3 conversion
If we look closer we do yet see another related, but non-negligible advantage: The typical downregulation of the conversion of the "inactive" thyroid hormone T4 to the "active" thyroid hormone T3 in response to long-term dieting was significantly reduced by the provision of leucine and (I will just go on a limb here and say "more importantly") the neurotransmitter precursor phenylalanine.
|Figure 2: Effect of weight cycling of markers of glucose and thyroid metabolism (Donato Jr. 2013)|
- Donato, J. et al. Effects of leucine and phenylalanine supplementation during intermittent periods of food restrictionand refeeding in adult rats. Life Sciences. 2007 [epub ahead of print]
- Iverson JF, Gannon MC, Nuttall FQ. Ingestion of leucine + phenylalanine with glucose produces an additive effect on serum insulin but less than additive effect on plasma glucose. J Amino Acids.
- Nuttall FQ, Schweim KJ, Gannon MC. Effect of orally administered phenylalanine with and without glucose on insulin, glucagon and glucose concentrations. Horm Metab Res. 2006 Aug;38(8):518-23.