Miley Cyrus has come under fire by registered dieticians after she promoted her new gluten-free lifestyle on "Twitter."

The 19-year-old star had hit back at rumors that she was anorexic after she appeared to lose a substantial amount of weight in recent weeks. The performer said that she had a gluten and lactose allergy and even told one fan that everyone should try no gluten for a week.

"The change in your skin, physical and mental health is amazing. You won't go back!" she wrote on her "Twitter" account. However, registered dietitian Rachel Begun told Today's Health that only those with a gluten-related disorder should cut the food group out.

"People who go gluten-free may gain weight if they rely mostly on highly processed gluten free foods," Rachel said. Another registered dietitian, Karen Ansel, also agreed.

"There's absolutely no evidence that a gluten-free diet promotes weight loss," Karen maintained. "However, there is data that indicates that following a gluten-free diet can result in a diet that's low in key nutrients," she added.

Cyrus, who has recently been photographed taking a lot of pilates classes and looking fit, may indeed be thriving on the challenging gluten-free diet and a tough regimen that cuts out wheat and some other grains.

However, experts say that her recommendation that everyone should try it is not on target. Gluten is a protein found in wheat, barley and other grains. Gluten-free diets have soared in popularity in recent years. Market research firm Packaged Facts projected in 2011 that sales of gluten-free foods and beverages in the U.S. would exceed $5 billion by 2015.

The diet is only strongly recommended for people who are diagnosed with celiac disease, a condition whose sufferers have an immune response to gluten in the small intestine. Celiac disease can cause pain, diarrhea and other digestive symptoms. Over time, potentially, it can result in permanent intestinal damage and malnutrition.