Worryingly, that figure looks set to continue rising.
Obesity has a complicated cocktail of causes, all of which need to be addressed before we can see any significant changes across society.
There are metabolic, psychological, social, and genetic factors to obesity, and these can all be present in individuals with obesity to differing degrees.
That said, if there was a simple, cost-effective drug that reduces appetite safely over the longer-term, it could make a huge difference.
Researchers from Helmholtz Zentrum München in Germany believe that they might have found such a chemical.
According to study author Dr. Paul Pfluger, doctors often ask people with obesity to lose 5–10 percent of their body weight each year, but this is rarely achieved.
Dr. Pfluger claims that "breaking through this 'magical barrier' is so important, as it leads to an improvement in metabolism and accompanying metabolic diseases such as type 2 diabetes."
Despite there being several lifestyle interventions, people struggle to meet their weight loss goals. Because of this, any new intervention that could provide a push in the right direction could have major benefits.
The scientists identified a potentially useful compound found in a plant used in traditional Chinese medicine. The chemical, called celastrol, is produced by the thunder god vine (Tripterygium wilfordii), which is native to South China.
The scientists found that, in obese mice, this compound activated satiety centers, or areas of the brain that tell us that we are full; effectively, it "switches off" hunger.
The most recent study to look at celastrol and its impact on obesity is published in the journal Diabetes.
"Celastrol reactivates the body's own mechanisms for controlling weight that would otherwise be switched off in obese individuals."
First study author Katrin Pfuhlmann, a Ph.D. student
Adipose tissue, or body fat, releases a hormone called leptin. When it binds to and activates leptin receptors, it triggers a feeling of being full. Some people become leptin resistant; this means that, although the chemical is still present in the blood and fat, it no longer elicits the same feeling of satiety, leading to overeating and obesity.
Pfuhlmann explains, "Normally those affected lose that feeling of fullness because the respective hormone — leptin — no longer has any effect. Celastrol, the compound we examined, restores leptin sensitivity and thus the sense of satiety."
Significant weight loss
Dr. Pfluger outlines the changes in behavior observed in the mice and their impressive weight loss:
"The administration of celastrol resulted in a much lower intake of food. Correspondingly, we observed an average loss of about 10 percent in body weight within 1 week."
We must now contain our excitement as we await the results from follow-up studies conducted in humans. However, Dr. Pfluger is confident that celastrol will work in the same way.
He explains that the leptin system in mice is almost identical to that in humans, so hopes are high. We may not have to wait too long, either; human trials are already under way in the U.S.
The authors are quick to explain that celastrol will not replace other lifestyle interventions, such as diet and exercise. It may, however, provide a useful boost to an individual's current weight loss efforts.