GLP-1 Agonists (Ozempic, Wegovy, and Mounjaro): Who should use them, and why a nutritionist is essential for success

In the ever-evolving landscape of weight management and metabolic health, GLP-1 agonists e.g., Ozempic, Wegovy, and Mounjaro have captured widespread attention. As a certified practising nutritionist (CPN) at FROM WITHIN, I’ve seen firsthand how these medications can transform lives when used appropriately. However, they’re not a magic pill, they require careful integration with lifestyle changes, particularly nutrition, to achieve sustainable results. In this article we explore what GLP-1 agonists are, who should consider them, the critical role of working with a nutritionist, and the potential negative effects if not used correctly. Backed by scientific evidence, we aim to provide balanced insights to help you make informed decisions about your health journey. Whether you’re struggling with obesity, type 2 diabetes, or related health conditions, understanding these medications is key.

What are GLP-1 agonists?

GLP-1 (glucagon-like peptide-1) agonists are a class of medications that mimic the action of the naturally occurring GLP-1 hormone, which is produced in the gut in response to food intake. This hormone regulates blood sugar levels, slows gastric emptying, reduces appetite, and promotes insulin secretion (Nauck & Meier, 2018). Originally developed for type 2 diabetes management, these drugs have gained popularity for weight loss due to their ability to induce satiety and reduce caloric intake.

Key examples include:

Ozempic (semaglutide): A once-weekly injectable approved by the TGA for type 2 diabetes. It works by enhancing GLP-1 receptor activity, leading to improved glycemic control and modest weight loss (Marso et al., 2016).

Wegovy (semaglutide): Essentially a higher-dose version of Ozempic, specifically approved by the TGA for chronic weight management in adults with obesity (BMI ≥30) or overweight (BMI ≥27) with weight-related comorbidities. Clinical trials, such as the STEP program, demonstrated an average weight loss of 15-20% over 68 weeks (Wilding et al., 2021).

Mounjaro (tirzepatide): A dual agonist that targets both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors, offering enhanced effects on weight and blood sugar. The SURMOUNT trials showed up to 22.5% weight loss in non-diabetic obese individuals, surpassing semaglutide in efficacy (Jastreboff et al., 2022).

These medications are administered via subcutaneous injection and have revolutionised obesity treatment by mimicking post-meal satiety signals, making them effective for long-term use when combined with lifestyle interventions (Davies et al., 2021). However, they’re prescription-only and should be initiated only under medical supervision.

Who should be on GLP-1 agonists?

Not everyone is a candidate for GLP-1 agonists; their use is guided by clinical evidence and guidelines from organisations such as the Australian Diabetes Society and the Royal Australian College of General Practitioners. Primarily, these medications are recommended for:

Individuals with type 2 diabetes: Ozempic and Mounjaro are first-line options for those with inadequate glycaemic control on metformin or other therapies. The SUSTAIN-6 trial showed semaglutide reduces cardiovascular events by 26% in high-risk patients, making it suitable for those with diabetes and heart disease (Marso et al., 2016).

People with obesity or overweight with comorbidities: Wegovy and Mounjaro are indicated for adults with a BMI of 30 or higher, or 27+ with conditions such as hypertension, dyslipidaemia, or sleep apnoea. Evidence from the STEP 1 trial supports their use in non-diabetic obese individuals, where participants achieved significant reductions in waist circumference and cardiometabolic risk factors (Wilding et al., 2021). Tirzepatide’s dual action makes it particularly effective for those with insulin resistance (Jastreboff et al., 2022).

Those who have not responded to lifestyle interventions: Guidelines emphasise trying diet and exercise first. A meta-analysis in JAMA found that GLP-1 agonists are most beneficial for patients who haven’t lost at least 5% body weight through behavioural changes alone (Khera et al., 2016).

Conversely, they’re not suitable for everyone, e.g., pregnant or breastfeeding individuals, those with a history of medullary thyroid carcinoma, or multiple endocrine neoplasia syndrome type 2 should avoid them due to potential risks (Therapeutic Goods Administration [TGA], 2023). Children under 12 are generally not candidates, though Wegovy is approved for adolescents aged 12+ with obesity. A study in The New England Journal of Medicine cautions against off-label use in those with normal weight, as it may lead to unnecessary side effects without proven benefits (Jastreboff et al., 2023).

The prescription of GLP-1 agonists should be determined by a healthcare provider through comprehensive assessments, including metabolic panels and psychological evaluations, to ensure alignment with individual health goals.

The importance of working alongside a nutritionist for maximum results

While GLP-1 agonists can kickstart weight loss and metabolic improvements, their true potential shines when paired with expert nutritional guidance. Evidence shows that medication alone often leads to plateaus or regain, whereas integrating nutrition yields sustainable outcomes (le Roux et al., 2020). At FROM WITHIN, I collaborate with clients on these medications to optimise results, focusing on personalised nutrition plans that enhance efficacy and prevent nutrient deficiencies.

GLP-1 agonists slow gastric emptying, which can reduce appetite but also increase nausea if not managed. A randomised controlled trial in Obesity demonstrated that participants on semaglutide who followed a structured low-calorie diet lost 18% more weight than those without dietary support (Wadden et al., 2021). At FROM WITHIN, we recommend high quality protein and fibre-rich meals to preserve lean muscle mass, as these drugs can lead to fat and lean tissue loss if calories are too restricted (Sargeant et al., 2023).

Secondly, working with a CPN ensures micronutrient adequacy. Rapid weight loss can deplete key nutrients such as vitamin B12, iron, and calcium, exacerbating risks in vulnerable populations (Astrup et al., 2022). Evidence from the SURPASS trials indicates tirzepatide users benefit from monitored supplementation to maintain bone health and energy levels (Frias et al., 2021).

Moreover, CPNs promote long-term adherence and behavioural change. A study in Diabetes Care found that combining GLP-1 agonists with behavioural therapy, including nutritional counselling, improved quality of life and reduced discontinuation rates by 40% (Garvey et al., 2020). This is crucial for "weaning off" the medication, as abrupt cessation often results in weight rebound. At FROM WITHIN, we guide clients on gradual dose tapering while building positive habits such as mindful eating and portion control.

Finally, personalised nutrition addresses comorbidities. For diabetic patients, it is paramount to design low-glycaemic plans to stabilise blood sugar synergistically with the medication (Nauck & Meier, 2018). In essence, my role is to help maximise benefits, turning short-term weight loss into lifelong health and wellness.

Negative effects if not used correctly

Despite their benefits, GLP-1 agonists can have serious negative effects if misused, underscoring the need for proper oversight. Common side effects include gastrointestinal issues such as nausea, vomiting, diarrhoea, and constipation, affecting up to 50% of users in the first months (Wilding et al., 2021). These often stem from improper dosing or rapid titration without dietary adjustments, leading to dehydration or electrolyte imbalances if unaddressed.

Another significant concern is the risk of gastroparesis, a condition characterised by delayed gastric emptying that can cause severe nausea, vomiting, bloating, early satiety, and abdominal pain. GLP-1 agonists inherently slow stomach motility as part of their mechanism, which can exacerbate or induce gastroparesis, particularly in long-term users or those with pre-existing gastrointestinal conditions. A population-based study in JAMA found that individuals using GLP-1 agonists for weight loss had a 66% higher risk of gastroparesis compared to non-users, with incidence rates around 0.53 events per 1000 person-years (Sodhi et al., 2023). The TGA has noted this in post-marketing reports, advising caution and monitoring for symptoms, as severe cases may require hospitalisation or discontinuation (TGA, 2023). This risk highlights the importance of starting at low doses and incorporating nutritional strategies, such as smaller, more frequent meals, to mitigate digestive slowdown.

More concerning is muscle loss (sarcopenia), particularly in older adults or those not engaging in resistance training. A study in The Lancet Diabetes & Endocrinology reported that up to 40% of weight lost on semaglutide is lean mass, increasing frailty risk if protein intake isn’t optimised (Wilding et al., 2022). Misuse, such as off-label use for cosmetic weight loss, can exacerbate this, as seen in reports of "Ozempic face" (sagging skin from rapid fat loss) (Jastreboff et al., 2023).

Pancreatitis, gallbladder issues, and thyroid tumours are rare but serious risks, with TGA Product Information including boxed warnings for medullary thyroid cancer based on animal studies (TGA, 2023). A meta-analysis linked long-term use to a 1-2% increased risk of acute pancreatitis (Azoulay et al., 2020). Psychological effects worsened eating disorders in susceptible individuals, have also emerged, with case reports of binge eating rebound post-discontinuation (Garvey et al., 2020).

Without nutritional support, nutrient deficiencies can lead to fatigue, hair loss, or weakened immunity. Over-reliance on the medication without lifestyle changes often results in yo-yo dieting, metabolic slowdown, and higher regain rates—up to 70% within a year off the drug (le Roux et al., 2020). Proper use, including medical monitoring and nutrition integration, mitigates these risks significantly. For those on or considering these medications, I ask you to prioritise a holistic plan that includes nutritional expertise for lasting results. If you’re exploring options, book in a consultation here to discuss how FROM WITHIN can support your journey safely. Remember, health transformations come from within, medication is just one piece of the puzzle.

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