We know that whey is considered the “fast” protein. Take it immediately after exercise, and you get a rush of amino acids that leads to the creation of bigger and stronger skeletal muscle fibers. But whey isn’t just whey. What’s interesting is that if you compare whole whey protein to the hydrolysate form, both produce an insulinotropic response. Whether it’s related to how fast the protein empties from the gut is another matter entirely.
In one study healthy men drank a 500-milliliter solution containing either 45 grams of whey protein or whey protein hydrolysate. Interestingly, both liquids took roughly 18 to 23 minutes to empty from the stomach. The maximum plasma insulin concentration occurred later—40 minutes vs. 60 minutes—and was 28 percent greater with the hydrolysate than with the whole whey.
That indicates that whey protein is an effective insulin secretagogue, but it’s even better if you use hydrolysate, which further augments the maximum insulin concentration by a mechanism unrelated to gastric emptying of the peptide solution.1 So perhaps it is the dipeptides and tripeptides found in the hydrolysate that contribute to greater insulin response. Would that also further contribute to postworkout anabolism? I think so.
We know that the presence of caseinomacropeptide, a mixture of glycosylated and nonglycosylated carbohydrate residues—in particular glycomacropeptide—in whey protein concentrate may be important for regulating body composition. Check out a rat study: The influence of whey protein and glycomacropeptide on weight gain and body composition was examined by feeding rats ad libitum for seven weeks with five diets differing in protein type: 1) casein; 2) barbecued beef; 3) no glycomacropeptide; 4) whey protein hydrolysate plus glycomacropeptide at 100 grams per kilogram of bodyweight; 5) hydrolysate plus glycomacropeptide at 200 grams per kilogram of bodyweight. The rats getting the most glycomacropeptide lost the most fat, so glycomacropeptide appears to have a significant additional influence on fat accumulation when combined with whey protein. Whey protein alone appears to have the dominant influence, accounting for 70 percent of the overall effect on bodyweight gain.2
A study compared the effects of glucose and whey-protein feedings on satiety and food intake as affected by time to the next meal and body composition in normal-weight and obese boys; the researchers discovered that whey protein suppressed food intake in the boys of normal weight but not in the obese ones. Whey normally acts as a potent stimulus to insulin and a prime regulator of body composition, but not if you’re fat.
I would highly recommend having a whey-based shake immediately after training—something on the order of 20 to 50 grams. If you’re looking to cut fat, include no carbs with that. If your immediate goal is total mass gain, however, add some carbs such as fruit—strawberries and bananas—to your shake. IM
Editor’s note: Jose Antonio, Ph.D., is a sports nutrition scientist, avid outrigger paddler and fan of Vince Flynn novels. Visit his Web site, www.joseantoniophd.com.
1 Power, O., et al. (2008). Human insulinotropic response to oral ingestion of native and hydrolysed whey protein. Amino Acids. In press.
2 Royle, P.J., et al. (2008). Whey protein isolate and glycomacropeptide decrease weight gain and alter body composition in male Wistar rats. Br J Nutr. 100:88-93.
3 Bellissimo, N., et al. (2008). A comparison of short-term appetite and energy intakes in normal weight and obese boys following glucose and whey-protein drinks. Int J Obes (Lond). 32:362-71.