Monday, March 8, 2010

Is Ghrelin Simply Related to Weight Loss?

In direct contradiction to the results discussed in the last post, Holdstock, et al. found that ghrelin levels do not fall precipitously after gastric bypass. In fact, they concluded that ghrelin responds to weight loss in a predicted manner . . . by increasing.

Holdstock, et al. measured four substances involved in metabolism that we will collectively call gut hormones: ghrelin, adinopectin, insulin and leptin. They compared the levels of these hormones in the blood of their research participants before gastric bypass, 6 months after, and 12 months after. In contrast to Cummings' results, Holdstock found that ghrelin increased only as participants lost weight, which is what we would expect under normal circumstances.

In another part of the study, Holdstock compared ghrelin levels in obese women who had had gastric bypass and those who had not. Perhaps you can anticipate the finding . . . there was no significant difference between the two groups.

As Holdstock concludes: "Apparently, further detailed studies are needed to fully elucidate the effect of gastrointestinal surgery on circulating ghrelin levels" (p. 3180). I know, I know. Just like a scientist to say we need more research. And more research we shall find.

I wonder, could the surgical techniques used in Uppsala, Sweden (Holdstock) differ enough from those used in Seattle, Washington (Cummings) to explain such disparate conclusions? I mean, is there a sweet spot in the stomach where ghrelin is produced, and sometimes it is surgically bypassed and sometimes it is not?
Holdstock, C. (2003). Ghrelin and Adipose Tissue Regulatory Peptides: Effect of Gastric Bypass Surgery in Obese Humans Journal of Clinical Endocrinology & Metabolism, 88 (7), 3177-3183 DOI: 10.1210/jc.2002-021734