I am a runner and I work out about 5 days a week. I am either running or in the gym doing cardio and lifting weights. Over the last year and a half I have lost 50 pounds and am in amazing shape. However since I am so active, and have low body fat I have stopped getting my period. I am wondering if this is affecting hormones in my body and if it is possible that it causes sexual side efftects such as loss of interest and arousal.
Secondary amenorrhea (loss of your period) is not unusual in female athletes who have very low body fat and/or exercise heavily. Yes, it definitely can affect your hormone balance, notably availability of estrogen in the body, and that can result in loss of interest and arousal.
There are also other factors that can produce secondary amenorrhea, and so it is a bit dangerous to simply attribute the loss of periods to weight loss or exercise, without evaluating to be sure that other possible causes are not present.
My recommendation would be that you consult your health care provider to have your secondary amenorrhea properly evaluated, and then appropriate management of the problem can be discussed.