Retatrutide: The Next Generation of Weight Loss Medication?
- AJ Hill Aesthetics
- 2 days ago
- 5 min read
Mounjaro... Wegovy... Ozempic. Big names in a growing industry. But are they in for some strong competition?
Retatrutide is an investigational medication currently being developed by Eli Lilly for the treatment of obesity and overweight.
Whilst it is not yet licensed for routine clinical use, it has generated significant interest because it targets three separate hormone receptors, rather than one or two as current weight loss medications do.
Early clinical studies have shown weight loss results that exceed those seen with current licensed medications such as Wegovy® (semaglutide) and Mounjaro® (tirzepatide). However, it is important to remember that retatrutide is still undergoing clinical trials to establish its long-term safety and effectiveness before regulatory approval is considered.
For people considering medical weight management, this highlights an important point: the newest medication is not always the best choice for every individual. Safe prescribing should always involve a comprehensive clinical assessment, ongoing monitoring, lifestyle support and regular review by an appropriately qualified healthcare professional.
How does retatrutide work?
Unlike existing medications that activate one or two metabolic pathways, retatrutide activates three:
1. GLP-1 (Glucagon-Like Peptide-1)
This is the same pathway targeted by:
Wegovy® (semaglutide)
Ozempic® (semaglutide)
Saxenda® (liraglutide)
GLP-1 helps by:
slowing stomach emptying
increasing feelings of fullness
reducing hunger
lowering food cravings
improving insulin release after meals
helping regulate blood sugar
2. GIP (Glucose-Dependent Insulinotropic Polypeptide)
This is also activated by:
Mounjaro® (tirzepatide)
GIP appears to:
improve insulin sensitivity
enhance satiety alongside GLP-1
reduce body fat
improve glucose control
make weight loss more sustainable
Researchers believe GIP helps reduce some of the gastrointestinal side effects often experienced with GLP-1 medicines, although this continues to be investigated.
3. Glucagon receptor
This is where retatrutide differs significantly.
Normally glucagon is known for increasing blood glucose, but when carefully balanced alongside GLP-1 and GIP stimulation it may also:
increase energy expenditure
stimulate fat metabolism
increase calorie burning
improve liver fat reduction
promote greater weight loss
Essentially, GLP-1 and GIP reduce calorie intake whilst glucagon may increase calorie expenditure.
This "eat less and burn more" approach is one of the reasons researchers believe retatrutide may produce unprecedented weight loss.
Comparing today's weight loss medications
Medication | Hormones targeted | Weekly injection | Average weight loss* |
Saxenda® | GLP-1 | Daily | 5–10% |
Wegovy® | GLP-1 | Yes | 15–17% |
Mounjaro® | GLP-1 + GIP | Yes | 20–22.5% |
Retatrutide (investigational) | GLP-1 + GIP + glucagon | Yes | Up to approximately 24% at 48 weeks in Phase 2 studies |
*Results vary depending on dose, duration of treatment, adherence to lifestyle changes and individual patient factors. Comparisons between different trials should be interpreted cautiously because study populations and designs differ.
What have the clinical studies shown - weight loss with Retatrutide
The landmark Phase 2 clinical trial published in the New England Journal of Medicine attracted worldwide attention.
After 48 weeks:
participants lost up to 24.2% of their body weight
many people continued losing weight when the study finished
researchers suggested weight loss may continue beyond one year
substantial reductions in waist circumference were also observed.
To put this into perspective:
Someone weighing 120 kg could potentially lose around 29 kg, although individual results vary considerably.
Blood sugar control
Retatrutide also demonstrated improvements in:
HbA1c
fasting blood glucose
insulin sensitivity
This makes it a promising candidate for people living with obesity and type 2 diabetes, although further studies are ongoing.
Fat loss
Studies suggest that most weight lost with retatrutide comes from body fat rather than lean tissue, although preserving muscle mass still depends on:
consuming adequate protein
undertaking resistance exercise
maintaining regular physical activity
These remain important parts of any medically supervised weight management programme.
Liver health
Researchers have also observed encouraging reductions in:
liver fat
inflammation associated with metabolic dysfunction-associated steatotic liver disease (MASLD, previously known as NAFLD)
markers linked to metabolic syndrome
Dedicated studies are underway to determine whether these benefits translate into meaningful improvements in liver disease outcomes.
Cardiovascular risk factors
Weight loss achieved with retatrutide has been associated with improvements in several cardiovascular risk markers, including:
lower blood pressure
improved cholesterol profiles
reduced triglyceride levels
better insulin sensitivity
As with other GLP-1-based therapies, dedicated cardiovascular outcome trials are needed to establish whether these improvements lead to reductions in heart attack, stroke or cardiovascular death.
Side effects
Because retatrutide stimulates GLP-1 receptors, the side effects are broadly similar to current GLP-1 medicines.
Common side effects include:
nausea
vomiting
diarrhoea
constipation
abdominal discomfort
bloating
reduced appetite
acid reflux
Most symptoms occur:
during dose escalation
within the first few weeks
after dose increases
They are usually mild to moderate and often improve as the body adapts, particularly when doses are increased gradually under clinical supervision.
Why clinical guidance remains essential
Although medications such as semaglutide, tirzepatide and, potentially in the future, retatrutide can be highly effective, they work best as part of a structured weight management programme.
A safe, clinically supervised approach should include:
a full medical assessment before treatment begins
screening for contraindications and medicines that may interact
gradual dose escalation to minimise side effects
regular monitoring of weight, blood pressure and relevant blood tests where appropriate
nutritional advice to ensure adequate protein, vitamins and hydration
support to maintain muscle mass through physical activity and resistance exercise
behavioural strategies to develop sustainable eating habits
regular follow-up appointments to review progress, manage side effects and determine whether treatment remains appropriate
People taking these medicines should also be advised about recognising symptoms that require prompt medical review, such as persistent severe abdominal pain, signs of dehydration or ongoing vomiting.
Medication alone is unlikely to provide lasting success without attention to nutrition, exercise, sleep and psychological wellbeing. Clinical support helps maximise benefits while reducing the risk of complications.
When might retatrutide become available?
Retatrutide is currently progressing through Phase 3 clinical trials. Before it can become routinely available in the UK, it must:
demonstrate long-term safety and effectiveness in larger populations
receive approval from the Medicines and Healthcare products Regulatory Agency (MHRA)
undergo assessment by the National Institute for Health and Care Excellence (NICE) for NHS use
become commercially available through licensed providers
Timelines depend on the outcome of ongoing studies and regulatory review.
The future of obesity treatment
Retatrutide represents one of the most promising developments in obesity medicine to date. By combining GLP-1, GIP and glucagon receptor activity into a single weekly injection, it has the potential to deliver greater weight loss than current therapies while also improving blood sugar control, metabolic health and markers of cardiovascular and liver disease.
However, it is still an investigational medicine, and important questions remain about its long-term safety, durability of weight loss and effectiveness across different patient groups.
For individuals seeking to lose weight safely, the most effective strategy remains a personalised, evidence-based programme that combines licensed medication (where appropriate), nutritional guidance, physical activity, behavioural support and regular clinical monitoring. This comprehensive approach not only improves the likelihood of achieving meaningful weight loss but also helps maintain those results while protecting overall health and wellbeing.
