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Whey Protein and Appetite

In recent years whey protein has emerged as the premier protein supplement for triggering gains in muscle size and strength. What makes that ironic is that in the past, it was considered a junk product of cheese manufacture and discarded. That changed when the nutritional properties of whey became evident.

Whey is one of two major milk proteins, the other being casein. Milk is 80 percent casein and 20 percent whey. A few years ago a highly publicized study found that the absorption rates of whey and casein varied, with whey getting absorbed fast and casein more slowly. It also found that the rapid uptake of essential amino acids from whey aided muscle protein synthesis when whey was taken in proximity to a workout, both before and after. The downside was that whey peaked in the blood in about an hour and was gone by the 90-minute mark. In contrast, casein curdled in the stomach, which led to a slow release of amino acids over a seven-hour period and helped with anticatabolic action in muscle.

That should tell you that the most complete supplement would incorporate both types of protein. On the other hand, whey is superior for taking right after a workout, especially when combined with simple carbs, since the combination boosts insulin release and, in turn, the activity of the rate-limiting enzyme for muscle glycogen synthesis. That aids recovery by replenishing muscle energy stores. Insulin also promotes the uptake of the essential amino acids required for muscle protein production.

Recent studies, however, show that a dose of 25 grams of whey protein alone is enough to maximize muscle protein synthesis following training and does not require added simple carbs to boost it. On the other hand, having an increased insulin surge after the workout from the simple carbs does more efficiently help replenish muscle and liver glycogen.

Since the introduction of whey protein supplements to the market, their popularity has grown because of their clear-cut help with muscle and strength gains when used in conjunction with intense weight workouts. Whey is preferred because of its rich content of the branched-chain amino acids—leucine, isoleucine and valine. The BCAAs are essential aminos, and while all three are important, leucine is superior. It plays a pivotal role in turning on metabolic pathways that upregulate muscle protein production.

In addition, whey contains a number of molecules that may help maintain health; for example, peptides, which are short chains of amino acids that can lower blood pressure. So there’s more to whey than just high-quality protein.

One of the more interesting aspects of whey is its effect on body composition. That’s also an aspect of casein to a lesser extent. In a study published a few years ago, casein proved superior to whey in aiding bodyfat loss in a group of policemen, mainly because of its longer-lasting protein release. Since protein itself helps tone down appetite, those findings make sense. More recent studies suggest that whey also potently helps reduce excess bodyfat.

One mechanism is the high BCAA content-—about a quarter of whey’s entire amino acid pool. BCAAs help release insulin, which helps control blood glucose. Having more stable blood glucose lowers appetite and helps tell your body to eat fewer calories, which results in lower bodyfat. Research has demonstrated that certain bioactive peptides in whey aid in the release of gut hormones that control food intake by sending signals to the appetite center in the brain.

In one study overweight and obese people with an age range of 18 to 65 were randomly divided into three groups1:

1) Those who got whey protein

2) Those who got casein protein

3) Control subjects, who got glucose, a sugar

The study lasted for 12 weeks. Those in the protein groups took two packets of protein a day, one 30 minutes before breakfast and the other 30 minutes before dinner. Both packets contained the same amount of protein—27 grams—and the same number of calories. They differed only in the type of protein they contained, either whey or casein.

After 12 weeks those in the whey group experienced a few beneficial changes that didn’t occur in the casein group. For example, blood triglycerides, or fats, dropped by 11 percent only in the whey group. The whey group also showed a 9.6 percent drop in low-density-lipoprotein cholesterol, which is linked to cardiovascular-disease, as are elevated blood triglycerides. A drop in LDL is considered good for cardiovascular disease prevention. Behind the favorable changes in blood lipids may have been whey influencing cholesterol synthesis in the liver, or a fraction of whey protein called beta-lactoglobulin may have inhibited cholesterol absorption in the intestines. Or the whey may have led to more rapid excretion of cholesterol. In contrast, past studies have shown that casein tends to favor higher blood cholesterol, along with higher LDL, apparently related to its low content of the amino acid cysteine.

While neither protein affected body composition, those in the whey group did have lower plasma insulin by the end of the study, and that favors bodyfat loss. Insulin is the body’s most potent fat-gain hormone. The entire basis of low-carb diets involves lowering insulin. So along with increased appetite control, whey would be expected to assist actively with bodyfat loss, particularly when you’re following a lower-carb diet. Indeed, it’s ideal to use under that condition, since the amino-acid-rich whey offsets muscle catabolism.

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1 Pal, S., et al. (2010). Effects of whey protein isolate on body composition, lipids, insulin, and glucose in overweight and obese individuals. Br J Nutr. In press.

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