NHMRC guidelines for obesity are outdated— expert advocates for a phenotype-based approach

No two people living with obesity present exactly the same way, and therefore management needs to be tailored to each individual, says Dr Georgia Rigas, a GP and senior bariatric physician at St George Private Hospital who will be speaking at Healthed’s upcoming webcast.

Although a range of treatments are available to manage obesity, the National Health and Medical Research Council guidelines are now outdated, according to Dr Rigas.

Fortunately, there’s a useful algorithm that can help guide GPs.

The algorithm, developed last year by the Australian Diabetes Society and the Australian and New Zealand Obesity Society, considers factors such as BMI, comorbidities, and individual goals and preferences to help guide treatment choices. It also recognises obesity as a chronic condition that requires ongoing management.

“The first step is intensive lifestyle modification. And I want to stress that this is the foundation upon which all the additional adjunct therapies are built upon”.

However, there are limitations, and it’s important that patients understand these.

“When people lose weight, they tend to go back to their setpoint, once they stop that particular intervention, and it’s incumbent upon us as healthcare professionals, to just take the time and explain to our patients why weight loss maintenance is difficult”.

“When a person with obesity loses weight by lifestyle interventions alone, we’re seeing an increase in their hunger hormone ghrelin and we see a suppression of the satiety hormones”, Dr Rigas explains.

“This, combined with a reduction in their metabolic rate, collectively is called metabolic adaptation. And it’s for this reason that people with obesity struggle to maintain their weight. It is not due to a lack of willpower. It’s quite the opposite. People are fighting their biology”.

Very low energy diets (VLED) have shown success as a first or initial phase of weight loss, but when the patient stops the diet, they regain weight.

It’s at this stage that Dr Rigas recommends GPs consider pharmacotherapy as an adjunct to VLED. As a combination therapy, patients can achieve double the amount of weight loss and it can be maintained in the long term.

With a wide range of TGA approved anti-obesity medications available to GPs, how do you choose what to prescribe?

Dr Rigas says “phenotyping” – understanding the eating behaviour patterns of your patient and prescribing a medication that works on that mechanism— can give the best results.

A pragmatic trial published in 2021 found four key phenotypes of obesity: hungry brain (abnormal satiation), emotional hunger (hedonic eating), hungry gut (abnormal satiety), and slow burn (decreased metabolic rate). Some participants (27%) had two or more phenotypes, and 15% had none.

The study found that participants randomised to the phenotype-guided approach had 1.75-fold greater weight loss at 12 months.

Which medicines were prescribed for each phenotype?

• Patients with abnormal satiation were given either phentermine‐topiramate extended release or lorcaserin (but the latter was discontinued following an FDA recall).
• Patients with abnormal hedonic eating (“emotional hunger”) were prescribed oral naltrexone/bupropion sustained release.
• Patients with abnormal satiety were prescribed liraglutide
• Patients with low predicted energy expenditure were prescribed phentermine 15 mg daily plus increased resistance training.
• When the patient fit more than one category, medication was chosen based on the predominant phenotype.

Source: Obesity (Silver Spring). 2021 Apr;29(4):662-671

Dr Rigas says it’s also important to remember that as obesity is chronic and progressive, lapses in management do occur. The 2022 National Obesity Strategy recommends that GPs proactively intervene if a person regains even a modest amount of weight.

Using VLEDs and pharmacotherapy in combination can be effective to achieve and maintain significant weight loss and improve comorbidities associated with obesity.

Additionally, regular monitoring and follow-up are important to reduce the likelihood of regaining weight.

“We need to be discussing weight with our patients on a regular basis. Obesity is a chronic disease and should be managed as such. We should not be afraid to have these conversations, as they are essential to the health and well-being of our patients.”

For more super practical and evidence-based tips on managing obesity in general practice, register here for Healthed’s webcast on Tuesday, 18 April, where Dr Rigas will be speaking.