Dieting: Nutrient Composition Probably Less Important than On-Going Low vs. High Carb Debate Suggests

In a soon to be published study Kerksick, et.al. (Kerksick. 2010) investigated the effect of 6 dietary regimens on weight loss in 141 obese women (38.7 +/- 8.0 yrs, 163.3 +/- 6.9 cm, 93.2 +/- 16.5 kg, 35.0 +/- 6.2 kg*m-2, 44.8 +/- 4.2 % fat). Interestingly, the members of all groups with restricted dietary intake + exercise achieved similar rates of weight loss (cf. Figure 1)

Figure 1: Changes in weight for High Energy Diet (HED), No Diet (ND), Very Low Carbohydrate High Protein Diet (VLCHP), Low Carbohydrate Moderate Protein Diet (LCMP), High Carbohydrate Low Protein Diet and no diet + no exercise Control (CON)

What I consider most important, though, is the statistical spread of the results. For me this confirms what I have been telling people over and over: There is no "one solution fits it all", it is quite obvious that - from a metabolic point of view - the low insulin level on low carb diets is a major plus (I am a low, but not no-carber, myself). Eating little to no carbs, on the other hand, just does not work out for some, so that they may eventually end up gaining weight instead of losing it (cf. Figure 1).

Bottom line: If you want to lose weight (not fat if you are already lean), eat less calories than you need, exercise and make sure you get proper amounts of nutrients (protein, fats, vitamins and minerals).

25g Whey Protein or 10g of EAAs Maximize Post Workout Protein Synthesis Without Additional Carbs

While this probably won't end the debate on whether post-workout carbohydrate intake is a good or a bad thing, a recent review of the literature presented by Steward M. Phillips at the The Summer Meeting of the Nutrition Society (Phillips. 2010) suggests that the addition of carbs to your post-workout shake is at least unnecessary, as long as you have a sufficient amount of leucine and EAAs in it:

The increment in [muscle protein synthesis] MPS is maximally stimulated at a dose of protein of approximately 25 g or 10 g EAA. This rise is based solely on protein consumption and is not augmented by carbohydrate, at least when protein is adequate.

Also, the type of protein is of utmost importance. Phillips recommends whey protein or (please note that it is not whey and EAAs) a blend of EAAs at dosages of 25g and 10g, respectively.

Figure 1: Whole blood leucine concentration (μM) following resistance exercise from subjects who consumed 500 ml fluid skim (low fat) milk and an isonitrogenous and isoenergetic quantity of a soya drink (drawn with data from Wilkinson et al.).

As can be seen from figure 1, even skimmed milk, which is only partially whey, produces a larger increase in whole blood leucine than soy protein (soy is for girls only, anyway ;-) Consequently, you should prefer dairy proteins or whey concentrates, isolates or hydrosolates as your post workout protein sources.

Skipping Breakfast Makes You Fat, but NOT by Increasing Appetite

You will certainly have heard of the scientifically proven correlation between skipping breakfast and getting obese. At least for children a group led by Tanya VE Kral (Kral. 2010) has now found "Omitting breakfast affected children’s appetite ratings but not their energy intake at subsequent meals." Astonishing as this may sound, the results of their investigation are unequivocal:

There was no significant main effect of breakfast condition on energy intake at lunch (P = 0.36) or throughout the remainder of the day (P = 0.85). There was a significant main effect of breakfast condition (P = 0.04) on total daily energy intake, which indicated that on the day when the subjects did not eat breakfast, they consumed 362 fewer calories over the course of the day than when they did eat breakfast. On the day when no breakfast was served, subjects
indicated that they were significantly hungrier, less full, and could consume more food before lunch than on the day when they did eat breakfast (P , 0.001).

Bottom line, eating less or rather not eating less by not eating at the right time makes children and most probably adults fat. As far as the reasons for this observation are concerned, the researchers speculate that ...

It is possible that children who regularly skip breakfast may show different energy intake patterns throughout the day compared with children who regularly eat breakfast and who may skip breakfast only occasionally. In other words, the long-term effects of skipping breakfast on energy intake may develop over time and may involve learning of new eating patterns.

These eating patterns will of course center around over-eating at night and would thus provide the body with an abundance of energy right when he needs it the least. It stands to reason that this may contribute to obesity, especially in view of the reduction in metabolic rate triggered by skipping breakfast. So, if you are one of those who "simply can't eat something in the morning", a meal replacement shake might be something worth considering.

15-30% Increase in Protein Synthesis if Protein is Ingested After Exercise

What common sense already told us has now been proven again in a scientific study published by the American Society for Nutrition (Pennings. 2010). Protein synthesis is greater if protein is consumed after exercise. And these results hold true for both, young and old.

As a marker of protein synthethis, the scientists investigated the response of exogenous phenylalanine on a 20-g bolus of intrinsically l-[1-¹³C]phenylalanine-labeled protein which was administered either at rest or after exercise:

[...] Muscle protein synthesis rates calculated from the oral tracer were 0.0620 ± 0.0065%/h and 0.0560 ± 0.0039%/h for the rest condition and 0.0719 ± 0.0057%/h and 0.0727 ± 0.0040%/h for the exercise condition in young and elderly men, respectively (age effect: P = 0.62; exercise effect: P < 0.05; interaction of age and exercise: P = 0.52).

So overall, this is a non-negligible increase in the calculated protein synthesis rate by 15% and 28% in the young and old subjects, respectively. It does however not answer the question, whether administration of the same 20g of marked protein right before exercise would not have increased protein synthesis to an even greater extent. Personally, I feel that for people on an everyday exercise regimen keeping protein intake high 24/7 will certainly be the best solution, even if it is just via an occasional protein shake at work (and thus probably "before workout).

L-Citrulline Against Arterial Stiffness

You probably know it from the ingredient list of your pre-workout or amino acid product, l-citrulline. Being a possible precursor of l-arginine it is included in those formulas to increase nitric oxide levels and deliver those "skin bursting pumps" the advertisements brag about.

In a recent study, scientists from Japan (Ochiai. 2010) found that 1 week of l-citrulline supplementation at 5.6g/day effectively reduced arterial stiffness in 15 healthy males:

Compared with the placebo group, baPWV [index of arterial stiffness] was significantly reduced in the l-citrulline group (p<0.01). No significant differences in blood pressure (BP) were found between the two groups, and no correlation was observed between BP and baPWV. The serum nitrogen oxide (NOx, the sum of nitrite plus nitrate) and NO metabolic products were significantly increased only in the l-citrulline group (p<0.05). Plasma citrulline, arginine and the ratio of arginine/asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase (arginine/ADMA ratio) were significantly increased in the l-citrulline group compared with the placebo group (p<0.05, p<0.01, p<0.05, respectively). Moreover, there was a correlation between the increase of plasma arginine and the reduction of baPWV (r=-0.553, p<0.05).

Beyond the reduction in arterial stiffness, these results confirm the hypothesis that l-citrulline effectively increases NO metabolism (probably even more than l-arginine) AND, what's even more important, reduces an endogenous inhibitor of NO synthase, so that more nitric oxide may be produced.