If luis goes on a diet and does not exercise, one of the negative effects of this regimen will be weight gain the loss of muscle tissue increased resting metabolism creeping obesity

The answer is loss of muscle tissue.  When you lose weight, you lose fat but if you continue to lose weight and the fat has been lost then and you would start losing muscle tissue.  This gives the person a gaunt-like appearance especially when he or she overdoes it.

i agree d is most definitely correct!