Roughly 120 overweight or obese patients from the Department of Veterans Affairs clinics in Durham, N.C., volunteered for a study comparing the effects of two different dieting plans—the low-carb, ketogenic diet (LCKD) and a low-fat diet in combination with orlistat (LFD+O), a weight-loss medication.

Sixty-five of the volunteers completed the low-fat diet, eating a diet with less than 30 percent of energy intake from fat and taking 120 mg of orlistat three times daily. Orlistat (Alli, Xenical) is an over-the-counter weight loss aid that can block a significant amount of fat from being absorbed by the digestive system. At the end of the 48-week trial, the group cut 8.5 percent of body fat. Low-carb dieters, on an Atkins-style diet, had similar results, trimming 9.5 percent of body fat.

“Both groups lost considerable weight (on average 21-25 pounds) and experienced numerous health benefits and were able to reduce medications for chronic diseases associated with weight,” explains Dr. William Yancy, Jr., M.D.,  research associate at Durham’s Department of Veterans Affairs and lead author of the study.

Although both plans tied for weight loss and had similar HDL (good cholesterol) improvements, the group of 57 low-carb dieters also had decreased systolic and diastolic blood pressure by 5.9 and 4.5 mm, respectively.

Pre-trial, average body mass index (BMI) was 39.3, and one in three participants had type 2 diabetes. A healthy BMI score for an adult ranges between 18.5 and 24.9. As the scores rises, the risk for complications such as stroke, type 2 diabetes, poor cholesterol and heart disease increases.

Following the study, low-fat dieters enjoyed better LDL (bad cholesterol) levels, while participants on the low-carb diet had improved insulin metabolism, hemoglobin A_1C, and blood glucose levels.

“People with these diseases—hypertension, high cholesterol, diabetes, arthritis—or at risk for these diseases stand to benefit the most (from these diets),” Yancy explains.

There haven't been significant health risks for short-term dieters, but little is known of the effects after six months. Long-term dieters may be at risk for bone loss or kidney stones. In any case, Dr. Yancy urges anyone considering a low-carb, ketogenic diet to consult a physician.

The study's abstract can be found in the Archives of Internal Medicine.