Saturday, March 26, 2011

Effects of Macronutrient Composition on Metabolic Signaling: Higher Protein Diet Favors Glycogen Storage in Muscle Over Adipose Tissue

Those of you who have already listened to the latest, revamped (and improved) episode of Dr Scott Connelly's BodyRx Show will already have heard of Suzanne Devkota's and Donald K Layman's study (Devkota. 2011) on the effects of different meal compositions on the postprandial glucose disposal. For the rest of you who have missed the episode and those of you who like their info white-on-black, here are the main results...

For 10 days, Devkota and Layman fed 60 rats a diet containing either 60% of energy from carbohydrates, 12% protein, 28% fat (CHO) or 35% carbohydrate, 35% protein, 30% fat (PRO) and evaluated plasma levels of insulin, glucose and C-peptide, as well as muscle and adipose tissue Akt, p70S6K and Erk 1/2 (markers of glucose and protein metabolism and cellular growth, respectively).

The graphs in figure 1 illustrate their most significant finding quite nicely. Other than in the case of the protein-fed rats, blood glucose is preferentially stored in fat tissue in the 30-90 min time window upon the ingestion of a meal in the high carb (CHO) group
Figure 1: Muscle and adipose tissue Akt expression (marker of glucose metabolism) after "high" protein (PRO) and high carbohydrate (CHO) meal, respectively (Devkota. 2011
The authors summarize this effect of macronutrient partitioning on metabolic signaling that is supported by the rest of their data as follows:
Animals chronically consuming the CHO diet produced greater metabolic signaling in adipose tissue to handle excess glucose and blunted signaling in skeletal muscle consistent with interpretation of insulin resistance. Conversely, animals consuming the PRO diet produced greater metabolic signaling in skeletal muscle with little signaling in adipose.
To fuel your workouts, it thus seems not only unnecessary, but even detrimental, to consume high amounts of carbohydrates. A "lower"  [note: even the high protein diet that was matched to the USDA's acceptable macronutrient distribution ranges (AMDR) had a carbohydrate content of 35% and thus a 1:1 protein to carb ratio!] carbohydrate intake, on the other hand, appears to prime your body to store glycogen primarily in muscle tissue. On a "high" protein, "lower" carb diet, you thus get the performance benefit without the unwanted fat gain and isn't this what we all are looking for?