One of the side effects of eating disorders is a rapid sense of satiety; that is, you feel more full when eating less food. Some of this is strictly physical, as the stomach shrinks during starvation, and food empties into the digestive tract slower. The formal medical name for this is delayed gastric emptying or gastroparesis. It almost always reverses upon normalization of eating patterns, but it can take a while. Some of this satiety may be anxiety-based (that stomach-churning feeling really isn't condusive to eating lasagna, let alone with gusto), and sometimes, it was a matter of my believing my own BS. If I just ate X, I damn well better be full!

Then, of course, we have to add neurochemicals to the mix. I've blogged several times on leptin in eating disorders (What's Leptin Got to Do With It?, Leptin and You, and Food and Sex and Leptin- Oh My!), and the protein, which signals satiety, has been much researched in relation to both anorexia and obesity. Gina Kolata's book Rethinking Thin has a great chapter on the discovery of leptin and some of the interesting research going on about the protein.

Ghrelin is kind of the ugly stepsister to leptin--it has the opposite function (ghrelin signals hunger as opposed to satiety), and it's gotten the shorter end of the stick in terms of research (at least recently). Unlike leptin, which is primarily synthesized by adipose tissue, ghrelin is synthesized in the stomach upon eating. A drop in ghrelin levels typically happens after eating and is thought to be linked to the release of insulin, which tells the body's cells to absorb the glucose from the meal.

Considering that people with anorexia are objectively starving, they generally have high levels of ghrelin as their bodies signal them to go get some food, levels that return to normal upon refeeding. However, a new study suggests that the excessive release of insulin by people with AN (known as hyperinsulinemia) also blunts the hunger-signaling effects of ghrelin. That is, the sudden drop in ghrelin upon eating even small amounts of food tells the brain that the person is full and the meal is finished.

The increased insulin sensitivity makes sense from a biological standpoint: the body will want to make the most use out of limited energy intake, so cells would do well to become more sensitive to insulin to slurp up more glucose. Whether the drop in ghrelin is an abnormality completely separate from the insulin sensitivity, or just a really ironic side effect, has yet to be seen. However, it adds another piece to the puzzle of why people with AN find it so difficult to eat more: they really do feel full.

One of the major criteria for diagnosing anorexia is amenorrhea- the absence of menstruation in women post-puberty but before menopause. The value of this criteria aside, amenorrhea is certainly an indicator that something is not quite right with your body. And that something usually has to do with an inadequate amount of fat on your body. Fat signals an appropriate energy reserve. Since menstruation takes energy (which is why you eat more right before your period), your body isn't going to waste it on something non-essential in the short term. Besides, thinks your body, she'll never be able to maintain a pregnancy with these energy reserves. So no period. Period.

Many female athletes report menstrual abnormalities, to the point where absent periods are just sort of thought to come with the territory. While researchers have known for a long time that too much exercise + too little food = loss of periods, the precise workings haven't been pinned down. Until now.

The culprit? Abnormalities in ghrelin levels. In research presented at the annual meeting of the Endocrine Society, age-matched high school female athletes who were not menstruating had higher ghrelin levels than those who continued to menstruate.

A press release titled "Hormone disorder may contribute to lack of menstruation in teenage athletes" said that:

The researchers studied 21 teenage athletes with amenorrhea, 19 normally menstruating athletes and 18 nonathletic girls. The body mass index, a measure of body fat, was lower in the amenorrheic girls than in the other two groups, but overall these athletes were not underweight. All girls were more than 85 percent of the ideal body weight for their ages. The amenorrheic group reported similar levels of physical activity as the normally menstruating group, and both groups of athletes reported more physical activity than the non-athletic group...

"These findings suggest that hormonal disorders may explain why amenorrhea occurs in some but not all adolescent athletes," Misra said. "In addition, ghrelin may be an important link between an energy deficit state and the hormones that regulate menstrual function."

I know that research presented at meetings tends to be much more preliminary, but all I could think while reading this was: didn't they think to check body fat levels? BMI is not the be-all and end-all of weight status. My periods stopped well within the "normal" weight range, above the target weight initially set for me at my first TWO hospital stays.* So their measurements might have left them scratching their heads a bit.

Also, there was no mention of whether these girls were screened for eating disorders before participating in the study. Which strikes me as something kind of important to look for.

I don't want to criticize the existence of such research because I do think it's important. Yet the elevated ghrelin levels, to me, simply say that this girl isn't eating enough for her activity level. Or that her activity level is too high for her food intake. It's not a hormone disorder. It's the result of an energy deficit. What I think is going on? Ghrelin levels are elevated when you aren't eating enough. The girls without their periods just aren't eating enough.

It would be interesting to look at ghrelin levels in athletes both during the current episode of amenorrhea and after menstruation resumes. This might help identify girls particularly at risk. But even if we do identify high-risk girls, I'm not so sure of the usefulness of such information. Because ALL girls should be eating enough to menstruate properly, ghrelin "disorder" be damned.

*And yes, I told them the actual weight at which my periods stopped. They still lowballed it. I didn't mind it at the time, but looking back, all I can do is shake my head.