Weight loss medications

by | Diet and Weightloss, Hormone Health

Dr Georgia Rigas

General Practitioner and Bariatric Physician

The physiological changes that occur in people living with obesity, such as metabolic adaptation, can limit weight loss – even when you’re eating very few kilojoules. As a result, achieving lasting weight loss can be extremely difficult. That’s where medical interventions such as prescription medications or bariatric surgery can be considered under the guidance of GPs and specialists.

If you have struggled to lose or maintain weight loss, after a medical assessment your GP may recommend a holistic approach incorporatingr prescription medication.These approaches are often used in combination with specialist meal replacement shakes to kickstart weight loss. Here, obesity expert Dr Georgia Rigas explains the different pathways that may be available to assist you on your weight loss journey.

Medications for weight loss

It is critical to note, weight loss medications are not a shortcut or cheat to get around changing your diet and exercise. “Anti-obesity medication (AOM) is meant to be used in addition to not in lieu of lifestyle interventions,” Dr Rigas says.

Australia’s Therapeutic Goods Administration (TGA) has strict criteria for GPs to prescribe oral and injectable medication for obesity treatment which includes medications to boost weight loss by suppressing appetite, reducing fat absorption or increasing metabolism. Prescription anti-obesity medications are an option for people with a BMI of at least 30 or between 27–30 with at least one obesity-related complication and must be used with ongoing diet and exercise.

Currently, Australia has only four medications approved for obesity management with three available now: phentermine (Duromine), which suppresses appetite; orlistat (Xenical) which reduces dietary fat absorption; and liraglutide (Saxenda), a synthetic version of the hormone glucagon-like peptide 1 (GLP-1).5 GLP-1 agonists work by changing the way the body handles reacts to glucose from food, appetite regulation and fullness. This is the same drug class as semaglutide (Ozempic) which is one of the most in-demand drugs internationally. The fourth medication is also version of the GLP-1 agonist semaglutide (Wegovy) that has been approved by the TGA for weight loss yet hasn’t physically arrived in Australia so can’t be prescribed.

The role of meal replacement shakes

They mightn’t taste as good as a typical protein shake but meal replacement shakes are designed for short-term use and help shift the way the body uses its stored up energy. “There are some very low energy meal replacements which have undergone vigorous clinical testing and have been proven to be effective in managing people living with obesity,” Dr Rigas says. “They can be used as a standalone therapy under the care of a medical doctor and experienced dietitian, with a view to eventually dovetailing to a portion controlled, nutritionally balanced eating plan.”

So what’s the science? “They’re very low in carbohydrates and so the body is forced to use up stored glycogen,” Dr Rigas explains. “After three to four days when all the glycogen is used up, the body then is forced to turn to stored fat for energy. This is when people start to lose weight.” 

The catch 22 of prescription medications

“The effective therapies for managing obesity are those which counterbalance metabolic adaptation,” Dr Rigas says. Revving up the metabolism can lead to far greater weight loss for more patients than lifestyle measures ever could. “They can yield 10 to 15 per cent weight loss which is clinically meaningful. Also, the majority of patients who respond to anti-obesity medication will be able to maintain the majority of that weight loss for longer time, as long as they continue the therapy,” Dr Rigas says.

And that’s the important caveat for using prescription medications for weight loss: they only work while you take them. “Like discontinuation of blood pressure lowering medication, once anti-obesity medications are stopped, then metabolic adaptation is no longer opposed and therefore weight regain occurs,” Dr Rigas says.