A skin patch that can “melt” fat – that is the latest development in treating metabolic disorders like diabetes and obesity.

Researchers at the Columbia University Medical Center and the University of North Carolina have devised this patch that can turn white fat into brown fat. White fat stores excess energy as large triglyceride droplets while brown fat contains smaller droplets and a higher number of mitochondria so that the body can burn these droplets to release energy. Brown fat is usually only found in newborn babies and the body burns this fat to keep them warm. By adulthood most of this brown fat is lost White fat is sometimes converted to brown fat in an adult body when it is exposed to cold temperatures.

There already exist several drugs that promote the “browning” of fat but these are available as pills or injections and the entire body is exposed to the drugs instead of fatty areas.The research team conducted an experiment in mice to examine the more direct delivery of browning drugs to fat tissue.

The team encases the drugs in nanoparticles, each about 250 nanometers in diameter, and then loaded them into a centimeter-square skin patch containing dozens of microscopic needles. When applied to skin, the needles painlessly pierce the skin and gradually release the drug from nanoparticles into underlying tissue. The treatment was tested in obese mice. Each mouse was given two patches – one with the drug-filled nanoparticles and another with empty nanoparticles. The patches were placed on either side of the lower abdomen. The study was controlled by giving another set of mice two empty patches. The researchers found that mice treated with the two drugs had a 20% reduction in fat on the treated side compared with the untreated side. They also had significantly lower fasting blood glucose levels than untreated mice. Genetic analyses also showed that the treated side contained more genes associated with brown fat than on the untreated side, suggesting that the observed metabolic changes and fat reduction were due to an increase in browning in the treated mice.

The study that was published in the journal ACS Nano shows that this treatment could be effective in getting rid of pockets of unwanted fat such as “love handles” and treat metabolic disorders, such as obesity and diabetes.

The patch has not been tested in humans yet. The researchers are currently studying which drugs will work best to promote localised browning and increase overall metabolism.