Losing weight can lead to Telogen Effluvium in which there is a sudden onset of severe hair fall, often in clumps together. This happens typically after a drastic weight loss session. In some cases the hair loss starts immediately and in other cases it can start even 2-3 months after the weight loss has actually occurred. Women are more vulnerable here as they are prone to sudden drop in their iron counts during menstrual cycles. This causes latent anemia which when coupled with weight loss makes women become easy targets for hair loss due to weight loss or crash dieting.