Weight of the world

New weapons are badly needed in the fight against obesity but developing drugs with lasting results and fewer side effects isn't easy.

- Nicky Pellegrino

Increasingly, obesity is being viewed as a complex disease rather than a lifestyle problem. The pandemic has accelerated this shift in attitude. The very overweight, and those suffering from associated conditions such as Type 2 diabetes and hypertension, have been hardest hit by Covid-19.

The World Obesity Federation predicts one billion people globally will be living with the disease by 2030. To treat it, a new generation of diet drugs is being developed, with the aim of greater weight loss and fewer side effects.

The history of diet drugs so far has been fairly inglorious. Medications have been introduced and then withdrawn as they were found to cause side effects as diverse as heart damage, cancer and suicidal thoughts.

In New Zealand, four weight-loss medicines are available currently, although none are subsidised. Xenical prevents some of the fat from food being absorbed by the body, and the others work in various ways to suppress appetite. All carry potential side effects - mostly gastrointestinal problems - and result in a relatively modest weight loss.

Developing better therapies is especially challenging because they need to fight against a survival mechanism. There are multiple pathways in the body that control hunger and satiety. If you lose one, then another can come into play, says Patrick Sexton, of Australia's Monash Institute of Pharmaceutical Science. An effective treatment therefore needs to be safe, well-tolerated and also target more than one pathway.

Another issue is that early drug trials tend to be done using rats, and they differ from humans in ways that may be significant.