Women: Large Deficits=Disruption in Ovarian Function

geekyjock76

*Edit*This is actually a repost from my thread earlier. I changed the name of the Subject to better market the thread by attracting more female readers since the subject matter specifically relates to them. Read on...

I've seen a lot of topics (not losing weight, hair loss, etc.) that are likely associated with the same cause: chronic caloric restriction and excessive exercise.

One common question people should ask themselves is: How much cardio (or exercise in general) in relation to a caloric deficit is excessive to the point it can be detrimental to ones health?

Anne B. Loucks has researched this topic extensively and, along with Jean R. Thurma, has estimated the threshold at which women may experience negative consequences associated with LH pulsatility and ovarian function due to the above mentioned lifestyle choices. The subjects in the research below were 29 regularly menstruating, habitually sedentary, young women of normal body composition for 5 days in the early follicular phase.

The formula to estimate this predicted threshold follows:

30 kcal/kg lean body mass x·days (at which you are at this deficit)

Energy availability is the amount of calories remaining once you subtract exercise calories from gross calories consumed. Basically, if your energy availability goes below the answer you get from the above equation, you are placing yourself at risk for the aforementioned health concerns - many of which can be quite serious and severe.

Here is the main findings of the research followed by the article:

"This experiment yielded three main findings: 1) LH pulsatility was disrupted abruptly at a threshold of energy availability not higher than 30 kcal/kg LBM·d; 2) the disruptive effects of subthreshold energy availability were bimodal, with substantially larger effects occurring in the subjects with the shortest luteal phases (11 d); and 3) the incremental effects of restricted energy availability on LH pulsatility most closely resembled those on glucose, β-HOB, GH, and cortisol."

http://jcem.endojournals.org/content/88/1/297.full?sid=3f3b16d8-b819-47c8-9cc9-88c8451b52dd

Finally, an example:

Equation: 30 kcal/kg of lean body mass x days

Female weighing 130 lbs with a lean body mass of 44.9kg and predicted TDEE of 2077.

30 kcal/44.9 x 5 days
threshold=6735 calories in a 5 day period (average of 1347 calories per day and a 45% deficit below maintenance)

Thus, anything greater than this deficit will illicit potential disruption in LH pulsitility and ovarian function after 5 days.