If she continues her current training and dieting, what are some of the potential outcomes

Marci and Joe are getting married in 3 months, and have decided to run a couple’s triathlon two weeks prior to the wedding. Marci’s wedding dress is still a size smaller than her current size, so she has been using the Atkins diet in an attempt to hit her target figure.  Joe and Marci’s training has been going very well, but lately, Marci has noticed a decrease in energy.  Explain to her the physiological basis for her lack of energy, as well as what she can do to remedy it.  If she continues her current training and dieting, what are some of the potential outcomes?