yes
Your body takes care of its fuel needs before it builds muscle. If you don't eat enough calories (& carbs) to cover your fuel needs, your body thinks it has to save fat stores for the famine it's facing & uses protein intake for fuel. It's a very inefficient fuel source & most nutrition experts will tell you it takes its toll on the body's organs.
Most sports nutritionists (ones w/ applicable college degrees & who have passed the R.D. exam) recommend a diet w/ at least 60% carbs. Using a intake of 1800 kcal/day, one should eat >270 grams of carbs/day. That's a fairly low calorie/day figure for a fitness enthusiast who isn't trying to lose weight.
If you'd like more information & details, check out a sports nutrition book. Nancy Clark, Liz Applegate, Ed Burke, & Ellen Coleman have good ones in print. They're all R.D.s except for Ed & his co-author is an R.D. Many libraries have these books.
Got the impression from your post your calorie level might be on the low side. Your body will hang onto fat if it thinks it's facing a famine (especially females).