Hair goes through stages:
(italics are cut and pasted from a hair website)

ANAGEN (GROWING) STAGE
The anagen stage is the growing period of a hair follicle.
This stage typically lasts about 3 to 5 years.
CATAGEN (INTERMEDIATE) STAGE
The catagen stage is the intermediate period of hair growth.
Hair follicles prepare themselves for the resting phase.
It lasts around 1-2 weeks.
During this phase, the deeper portions of the hair follicles start to collapse.
TELOGEN (RESTING OR SHEDDING) STAGE
The telogen stage is the resting and shedding period of the hair cycle.
It usually lasts 3 to 4 months.
At the end of this period, older hairs that have finished their life will fall out and
newer hairs will begin to grow.

When some extreme stress happens in your life, like a pregnancy, or starvation, surgery or even quick weight loss, a large amount of hair can suddenly enter the telogen stage but since that stage lasts 3-4 months (the hairs resting before they fall out) you have to look back at what happened in your life then. When I first started Atkins, I lost 30 lbs in 3 months and at almost exactly 4 months I had significant hair loss. It lasted a few weeks to my dismay, but stopped eventually with no significant bald spots, and ever since (4+ years) I have experienced very little shedding and way better growth and thickness than I ever had in my life - attributed to my improved diet!

I don’t believe that a lowered amount of protein will result in hair loss, unless 3-4 months ago you suddenly switched to eating almost none. I suspect it is simply your bodies reaction to the stress of your weight loss.

http://forum.lowcarber.org/showthread.php?t=355017