Although man may not be able to live on bread alone, some best-selling diet authors seem to recommend against living on bread at all.

A resurgence in interest in the high-protein, low-carbohydrate diet has prompted two UT Southwestern researchers to zero in on the fad diet to see if it increases the risk of kidney stones and loss of bone.

Dr. Shalini Reddy, assistant professor of internal medicine, and Dr. Chia-Ying Wang, postdoctoral fellow in internal medicine, hope to have final results of the first phase of a two-phase study soon. They decided to examine the high-protein, low-carbohydrate diet after meeting with Dr. Charles Pak, director of the Center for Mineral Metabolism and Clinical Research at UT Southwestern and assistant dean for clinical investigation. Dr. Pak had learned that some patients who had been on the regime were being diagnosed with kidney stones.

People may lose weight, "but it's not a healthy way to live," Dr. Reddy said of the protein heavy diet.The study will provide information on the subject's level of acidosis, which is caused by the enhanced production of ketone bodies. Ketone bodies are found in the blood and urine because of excess oxidation of fatty acids by the liver, something that can happen in starvation, in pregnancy or in diabetes.One factor that increases kidney-stone risk in the low-carbohydrate diet is the acidic content of animal flesh and the lack of alkaline foods in the diet, Dr. Reddy said.

In the first phase of the study subjects will be asked to eat a regular diet for two weeks followed by two weeks of a highly restrictive diet that has less than 20 grams of carbohydrates. Participants then will eat a less-restrictive diet for the final four weeks.

During the last five days of each of these stages, subjects will stay overnight in UT Southwestern's General Clinical Research Center in Parkland for testing.If the doctor's suspicions about ketosis are confirmed in the first phase, Dr. Reddy and Dr. Wang will begin a second phase. That phase will look at countermeasures to the increased risk of kidney stones."There's always a trade-off," Dr. Wang said. "The trade-off here is brittle bones and the formation of kidney stones."

Dr. Pak said the much-needed study "promised to provide not only an objective look at the potential dangers of a high protein-low carbohydrate diet, but also yield a countermeasure that would allow a person to take the diet and derive the benefit of losing weight without harmful side effects