Researchers have warned that a new procedure to lose weight is causing patients to lose muscle and fat.
Embolization of the left gastric artery is being explored as an alternative to invasive gastric bypass, but it has an unexpected side effect.
Obesity is a major health problem around the world, related to serious diseases such as heart disease, cancer and diabetes. At age four, 10 percent of children are obese, reaching 20 percent at the age of 10. In adulthood, this again increases to 25 percent.
First-line treatments, such as diet and exercise, often do not work, leading many patients to opt for gastric bypass surgery, a successful procedure known to help morbidly obese people lose weight.
The researchers said that the loss of muscle mass is worrying and stresses the importance of adequate nutritional advice after the procedure
A gastric bypass involves tying a band around the stomach to make it smaller, but it carries significant costs and possible complications.
Currently under investigation in clinical trials, embolization only requires reducing blood flow to the upper part of the stomach, called fundus.
People feel hungry when the hormone ghrelin is released from the bottom, so research believes that reducing the flow of blood to the stomach would delay the release of ghrelin and, therefore, decrease hunger.
In the procedure, the microscopic beads are injected under image guidance into the artery that supplies blood to the stomach.
It has been shown to be successful in reducing weight, but an undesired side effect was significant muscle loss.
The researchers said the loss of muscle mass is worrisome and underscores the importance of adequate nutritional counseling after the procedure.
The lead author, Dr. Edwin Takahashi, a vascular and interventional radiology researcher at the Mayo Clinic in Rochester, Minnesota, said: "There has been a lot of research focused on the effectiveness of gastric artery embolization to lose weight.
"However, there has been no data on what contributes to weight loss, whether patients are losing fat, as desired, or muscle mass, or some combination of the two."
For more information, Dr. Takahashi and his team studied computed tomography scans of 16 overweight or obese patients who had undergone gastric artery embolization to treat gastrointestinal bleeding.
CT scans, when used in conjunction with special software, allow measurements of body composition based on different tissue densities such as fat and muscle.
The scans were performed before and about a month and a half after the procedure.
The results were compared with those from a control group of 16 outpatients who did not undergo embolization of the left gastric artery, but who underwent computed tomography scans at two different periods for non-specific abdominal pain.
The 16 individuals experienced significant weight loss after the embolization procedure, losing an average of 6.4 percent of their body weight for a month and a half.
The body mass index, a measure of body weight in relation to a person's height, fell by 6.3 percent.
While weight loss was not surprising to researchers, changes in body composition were.
The skeletal muscle index, a measure of the amount of muscle that connects to the skeleton and helps move the limbs, dropped 6.8 percent.
Skeletal muscle is important for health, and its loss can affect physical function and metabolism and make a person more at risk of injury.
Dr. Takahashi said: "The significant decrease in the amount of skeletal muscle highlights the fact that patients who undergo this procedure are at risk of losing muscle mass and should be managed accordingly after the procedure.
"We must make sure they receive adequate nutrition to minimize the amount of muscle tissue they lose."
The patients also lost a significant amount of body fat.
His overall body fat index was reduced by an average of 3.7 percent.
However, much of the fat loss was subcutaneous or the fat that is found directly under the skin.
Visceral fat, the most dangerous fat that surrounds organs and associated with serious health problems such as heart disease and diabetes, did not decrease significantly during follow-up.
The researchers plan to expand their studies in the future to include people who are specifically undergoing embolization as a treatment for obesity.
The study was presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago.