Obesity and overeating have reached global epidemic levels, affecting an estimated 1.9 billion people worldwide. They pose great risks to health, as they are associated with the development of conditions like diabetes, cardiovascular and musculoskeletal diseases, and certain types of cancer. Obesity is considered by many specialists to rank among the top leading causes of preventable death, although exact figures are difficult to calculate. By 2008, the economic burden of obesity in Canada due to direct health costs and indirect losses in productivity reached a value of 4.6 billion dollars.
Obesity develops when the energy consumed by the body largely surpasses the energy spent. Any treatment directed at correcting obesity must either reduce energy intake, increase energy expenditure, or achieve a mixture of both. Caloric diet and physical exercise are the most common strategies directed, respectively, at the first and second goals. However, on a population scale, the results of these strategies are not so bright, which is why health practitioners are seeking alternatives.
One of the avenues being explored involves increasing the efficiency and expenditure of adipose fat tissues. An interesting target is brown adipose tissue (BAT for short; the brown color is due to a large number of mitochondria that are rich in iron). This tissue was discovered in newborn babies and later in adults, as being responsible for generating heat at the expense of large quantities of stored energy. In addition, other heat generating cells – brites – were found to develop in white adipose tissue (WAT or fat), essentially converting it into BAT.
Informed by these findings, researchers began looking for drugs that could activate BAT and recruit brites inside WAT. In a recent study published in Molecular and Cellular Biochemistry, Hilal Parray and Jong Yun from Daegu University in South Korea present compelling evidence that cannabidiol (CBD) could be a good candidate.
Different concentrations of CBD were added to in vitro mouse WAT cells still in development. Contrary to controls, CBD promoted the “browning” of WAT in a dose dependent manner, activating both BAT genes and proteins. Furthermore, the maximum concentration of CBD administered did not incur any noticeable damage to the cells.
The authors then looked for indications that CBD could also increase the metabolic activity of WAT. Indeed, CBD promoted the breakdown of fat (lipolysis) while inhibiting its formation (lipogenesis). When fat content was directly measured, it was found to be the lowest in the CBD treatment condition (see figure below). Final tests enabled the researchers to pinpoint one receptor and enzyme involved in these metabolic effects of CBD.
Previous studies had shown that CBD could prevent weight gain, but the question remains whether it can also decrease it. The novel finding presented in this study that CBD promotes heat generation (or “browning”) in white adipose tissue strongly suggests this may be the case. In vivo studies are now necessary to test this hypothesis, before a better evaluation of CBD’s potential therapeutical effects in obesity can be made.