Another group of peptide fractions called lactokinins “have been shown to inhibit a compound called angiotensin-converting enzyme, or ACE,” Bargetzi continues. “If unhindered, ACE encourages fat cells to grow. The calcium in whey, meanwhile, suppresses a different set of hormones that also stimulate fat cells. In combination with branched-chain amino acids, the lactokinins and calcium all work to direct the body’s energy away from producing fat and into producing muscle.”
Research on the appetite-stimulating hormone ghrelin led the popular press to tout it as the “fat hormone.” As Greenblum points out, “plasma ghrelin concentrations do follow a cyclical pattern, increasing before meals and decreasing shortly thereafter.” The postprandial reduction in its levels, she says, is influenced by the relative proportion of macronutrients in a meal, “with a greater decrease after protein and carbohydrate ingestion than after fat ingestion.” However, she notes, “increased satiety and reduced appetite associated with an increased dietary protein intake may not be mediated by ghrelin homeostasis.”
That uncertainty underscores our understanding of proteins and weight-management hormones. As Pikosky puts it: “Currently, there is not a clear understanding of the role of different proteins on satiety and weight management. Studies have examined the meal effect of different proteins on satiety and subsequent food intake in the short term. While some studies have shown differences between protein sources, others have not. Confounding issues contributing to these mixed results include differences in study design, how the protein is provided—is it a single nutrient vs. part of a meal?—timing of when satiety is assessed, and the amount of protein provided.”
We’ve still a lot to learn.
Kimberly J. Decker, a California-based technical writer, has a B.S. in consumer food science with a minor in English from the University of California, Davis. She lives in the San Francisco Bay Area, where she enjoys eating and writing about food. You can reach her at kim@decker.net.