For people unable to maintain weight loss due to their genetic predisposition to obesity, a new an injectable drug widely used to lower blood sugar levels can help fight the weight gain, suggest a study.

Around two to six per cent of all people with obesity develop obesity already in early childhood because they are genetically programmed to do so. Obesity-causal mutations in one of their "appetite genes" gives them a strong genetic predisposition for developing obesity, also called monogenic obesity. Their experience of hunger is over-ruling and their feeling of satiety limited.

Researchers discovered that this group of people with obesity can lose weight with the help of the medicine liraglutide -- a modified form of the appetite-inhibiting hormone GLP-1 naturally secreted from the intestine when we eat. "The appetite-inhibiting drug liraglutide has a positive effect on them. They feel less hungry and lose six per cent of their body weight within four months," said lead author Signe Sorensen Torekov, associate professor at the University of Copenhagen in Denmark.

In the study, published in the journal Cell Metabolism, the team have examined a small group with obesity caused by pathogenic mutations in the so-called MC4R gene and those with obesity without the mutations. Both groups were treated with the medicine for four months; no changes were made to their diet and level of exercise in this period.

The individuals with this most common form of monogenic obesity lost 7 kg of their body weight compared to 6 kg for the people with common obesity. Medicine acting as an analogue to our natural GLP-1 hormone is already available, as it has been approved by both the US Food Drug Association and European Medicines Agency for the treatment of obesity and Type 2 diabetes.

The study thus makes it possible to treat the most common form of genetically caused obesity, where patients respond poorly to existing treatments, the researchers noted. As MC4R mutations cause obesity already in early childhood, the researchers hope the results can pave the way for new studies on young people in the future.