Although the above would probably be the major mechanisms by which whey could help the dieter, there are several secondary effects of whey that may assist in weight loss. For example, whey’s effects on serotonin levels. Serotonin is probably the most studied neurotransmitter since it has been found to be involved in a wide range of psychological and biological functions. Serotonin ( also called 5-hydroxytryptamine or 5-HT) is involved with mood, anxiety, and appetite.
Elevated levels of serotonin can cause relaxation and reduced anxiety. Low serotonin levels are associated with low mood, increased anxiety (hence the current popularity of the SSRI drugs such as Prozac and others), and poor appetite control. This is an extremely abbreviated description of all the functions serotonin performs in the human body - many of which have yet to be fully elucidated - but a full explanation is beyond the scope of this article.
Needless to say, Increased brain serotonin levels are associated with an improved ability of people to cope with stress, whereas a decline in serotonin activity is associated with depression and anxiety. Elevated levels of serotonin in the body often result in the relief of depression, as well as substantial reduction in pain sensitivity, anxiety and stress. It has also been theorized that a diet-induced increase in tryptophan will increase brain serotonin levels, while a diet designed for weight loss (e.g., a diet that reduces calories) may lead to a reduction of brain serotonin levels due to reduced substrate for production and a reduction in carbohydrates.
Many people on a reduced calorie intake in an attempt to lose weight find they are often ill tempered and more anxious. Reductions in serotonin may be partially to blame here. One recent study (The bovine protein alpha-lactalbumin increases the plasma ratio of tryptophan to the other large neutral amino acids, and in vulnerable subjects raises brain serotonin activity, reduces cortisol concentration, and improves mood under stress. Am J Clin Nutr 2000 Jun;71(6):1536-1544) examined whether alpha-lactalbumin - a major sub fraction found in whey which has an especially high tryptophan content - would increase plasma Tryptophan levels as well reduce depression and cortisol concentrations in subjects under acute stress considered to be vulnerable to stress.
The researchers examined twenty-nine "highly stress-vulnerable subjects" and 29 "relatively stress-invulnerable" subjects using a double blind, placebo-controlled study design. The study participants were exposed to experimental stress after eating a diet enriched with either alpha-lactalbumin (found in whey) or sodium-caseinate, another milk based protein. They researchers looked at:
* Diet-induced changes in the plasma Tryptophan and its ratio to other large neutral amino acids.
* Prolactin levels.
* Changes in mood and pulse rate.
* Cortisol levels (which were assessed before and after the stressor).
Amazingly, the ratio of plasma Tryptophan to the other amino acids tested was 48% higher after the alpha-lactalbumin diet than after the casein diet! This was accompanied by a decrease in cortisol levels and higher prolactin concentration. Perhaps most important and relevant to the average person reading this article, they found "reduced depressive feelings" when test subjects were put under stress.
They concluded that the "Consumption of a dietary protein enriched in tryptophan increased the plasma Trp-LNAA ratio and, in stress-vulnerable subjects, improved coping ability, probably through alterations in brain serotonin." This effect was not seen in the sodium-caseinate group. If other studies can confirm these findings, whey may turn out to be yet another safe and effective supplement in the battle against depression and stress, as well as reduced serotonin levels due to dieting.
Although there is a long list of hormones involved in appetite regulation, some of which have been mentioned above, serotonin appears to be a key player in the game. In general, experiments find increased serotonin availability or activity = reduced food consumption and decreased serotonin = increase food consumption. If whey can selectively increase serotonin levels above that of other proteins, it could be very helpful to the dieter.
Other possible advantages whey may confer to the dieter is improved blood sugar regulation (Frid AH, Nilsson M, Holst JJ, Bjorck IM. Effect of whey on blood glucose and insulin responses to composite breakfast and lunch meals in type 2 diabetic subjects. Am J Clin Nutr. 2005 Jul;82(1):69-75.) which is yet another key area in controlling appetite and metabolism.
Finally, calcium from dairy products has been found to be associated with a reduction in bodyweight and fat mass. Calcium is thought to influence energy metabolism as intracellular calcium regulates fat cell (adipocyte) lipid metabolism as well as triglyceride storage. It’s been demonstrated in several studies the superiority of dairy versus non-dairy sources of calcium for improving body composition, and the whey fraction of dairy maybe the key.
The mechanism responsible for increased fat loss found with dairy-based calcium versus nondairy calcium has not is not fully understood but researchers looking at the issue theorized "... dairy sources of calcium markedly attenuate weight and fat gain and accelerate fat loss to a greater degree than do supplemental sources of calcium. This augmented effect of dairy products relative to supplemental calcium is likely due to additional bioactive compounds, including the angiotensin-converting enzyme inhibitors and the rich concentration of branched-chain amino acids in whey, which act synergistically with calcium to attenuate adiposity."
It appears components in whey - some of which have been mentioned above - are thought to act synergistically with calcium to improve body composition (Zemel MB. Role of calcium and dairy products in energy partitioning and weight management. Am J Clin Nutr. 2004 May;79(5):907S-912S.).
Conclusion
Taken in isolation, none of these studies are so compelling that people should run out and use whey as some form of weight loss nirvana. However, taken as a total picture, the bulk of the research seems to conclude that whey may in fact have some unique effects for weight loss and should be of great use to the dieter. More studies are clearly needed however.
So what is the practical application of all this information and how does the dieter put it to good use? Being the appetite suppressing effects of whey appear to last approximately 2-3 hours, it would seem best to stagger the intake throughout the day. For example, breakfast might be 1-2 scoops of whey and a bowl of oatmeal, and perhaps a few scoops of whey taken between lunch and dinner.
If whey does what the data suggests it does in the above, that should be the most effective method for maximizing the effects of whey on food (calorie) intake on subsequent meals as well as the other metabolic effects covered. If working out, the schedule may be different however and people should follow the pre and post nutrition recommendations made in my ebook "Muscle Building Nutrition" or advice easily found on the 'net via the many sports nutrition and bodybuilding related web sites.
