Retatrutide (Reta): Weight Loss Results, Muscle Loss & Strength Training
Last reviewed: 18 October 2026
Important: Retatrutide is an investigational medicine. As of October 2026 it is not approved by any regulator, including in the UAE, and is legally available only to participants in Eli Lilly's clinical trials. This article is for education only and is not medical advice. Pull Gym does not provide, prescribe or supervise any medication.
If you've seen "Reta" on social media, you've probably also seen the headlines: weight loss close to what people expect from bariatric surgery. Retatrutide is the most talked-about weight-loss drug in development, and its trial results are genuinely striking.
But there's a question the headlines rarely answer. When someone loses a quarter of their body weight, what happens to their muscle, their strength and their ability to move well? That's where training comes in. Here's what the research shows, what it doesn't, and what it means in practice.
What is Retatrutide?
Retatrutide is a once-weekly injection being developed by Eli Lilly. It's a single molecule that activates three hormone receptors involved in appetite and metabolism: GIP, GLP-1 and glucagon (Lilly). That's why it's called a "triple agonist". "Reta" is simply the online nickname. You may also see it called a "GLP-3", but Lilly points out that this label is scientifically inaccurate.
How is Reta different from Mounjaro and Wegovy?
Semaglutide (Wegovy, Ozempic) activates GLP-1.
Tirzepatide (Mounjaro, Zepbound) activates GIP and GLP-1.
Retatrutide adds a third target: glucagon.
The glucagon component is the main scientific difference. How much it adds in real-world terms is still being studied, and no head-to-head trial comparing Retatrutide with tirzepatide has reported results. So "Reta vs Mounjaro" can't yet be answered with a direct comparison, only with separate trials in different populations.
What the clinical trials show
Retatrutide has now been tested in five Phase 3 trials, all reporting positive results.
TRIUMPH-1 (2,339 adults with obesity or overweight and a weight-related health condition, without diabetes): participants on the highest dose lost an average of 28.3% of body weight over 80 weeks, compared with 2.2% on placebo. Almost half on that dose lost 30% or more (Lilly, May 2026). Results were later published in the New England Journal of Medicine.
TRIUMPH-2 (adults with obesity and type 2 diabetes): up to 20.8% average weight loss at 80 weeks.
TRIUMPH-3 (severe obesity and established heart disease): up to 22.6% at 80 weeks (Lilly, July 2026).
Trial averages are not personal predictions
These figures are averages from carefully controlled trials, often calculated as if everyone stayed on treatment. Some participants lost far more, others far less, and some stopped because of side effects. When analysed regardless of whether people kept taking the drug, the top-dose result in TRIUMPH-1 was 25.0% rather than 28.3%. Your own outcome would depend on your health, your starting point and the medical care you receive.
Retatrutide side effects
The most common side effects were digestive, similar to other drugs in this class. In TRIUMPH-1, nausea affected up to 42% of participants on Retatrutide, with diarrhoea, constipation and vomiting also common. Some people reported dysesthesia, an unusual skin sensation, which was mostly mild to moderate. On the highest dose, about 11% stopped treatment because of side effects, compared with about 5% on placebo.
These effects matter for anyone thinking about exercise. Nausea, low appetite and fluid loss all affect how well you can train and recover.
Is Retatrutide available in Dubai or the UAE?
No. In July 2026 the Emirates Drug Establishment stated that Retatrutide remains in clinical trials and is not approved for use or distribution in the UAE. The regulator also took action against sellers of unapproved peptide weight-loss products (Khaleej Times).
Lilly says it plans to submit Retatrutide to the US FDA in early 2027. Approval and launch timelines elsewhere, including the UAE, are not confirmed. Products sold online as "Retatrutide" or "research peptides" are not legitimate medicines and may contain the wrong ingredient, the wrong amount or contaminants. If you're interested in medical weight-loss treatment, speak to a licensed doctor about approved options.
Does Retatrutide cause muscle loss?
Any large weight loss involves losing some lean mass along with fat. The question is how much, and what that means for strength and function.
So far, the only published body-composition data for Retatrutide come from a Phase 2 substudy of 189 adults with type 2 diabetes, measured with DXA scans over 36 weeks. Fat mass fell by up to 26%. Lean mass also fell, but the researchers concluded that the share of weight lost as lean mass was similar to other obesity treatments, not disproportionately high (Coskun et al., Lancet Diabetes & Endocrinology, 2025).
That's reassuring, but limited. It was a small study, in one population, over a shorter period than the Phase 3 trials. Phase 3 body-composition results have not yet been published.
Lean mass is not the same as muscle
DXA "lean mass" includes muscle, but also water, organs and connective tissue. A drop in lean mass doesn't tell you exactly how much skeletal muscle was lost. Some of it reflects the body simply carrying less weight.
A smaller body is not automatically a stronger one
None of the Retatrutide trials so far has reported strength or physical performance as a main outcome. Losing weight can make movement easier, but strength, power and fitness don't improve on their own. If you lose significant weight without training, you may end up lighter but not necessarily more capable.
Why strength training matters during major weight loss
Here's where the evidence shifts from Retatrutide muscle loss specifically to weight-loss medicines more broadly. A 2026 consensus statement from European obesity, dietetic and patient organisations recommends that people using incretin-based medicines prioritise preserving lean mass through adequate protein, fluids and nutrient-dense food, alongside resistance training (EASO/EFAD/ECPO, 2026).
Research in general adult populations also shows that supervised resistance training over 10 weeks or more can meaningfully increase lean mass and strength (review, 2026). Strength training can't guarantee you'll keep every kilogram of muscle. What it gives you is the best available tool to protect strength, movement quality and long-term function while the scale moves.
Weight loss is only one part of a physical transformation. Keeping your strength, moving well and building fitness that lasts takes a structured plan that adapts to how you feel week to week. If you'd like help putting these principles into practice, see how Pull Gym's personal coaching works.
A simple strength training framework
The following is an illustrative example for healthy adults, not a personal prescription. The same principles apply whether someone is using an approved weight-loss medicine like retatrutide and muscle loss, following a diet, or neither.
Before you start: get clearance from your doctor, especially if you're on medication, have a medical condition, or haven't trained in years.
Lift two to three times a week. WHO recommends muscle-strengthening activity on two or more days a week (WHO). Full-body sessions work well.
Train the main movement patterns: a squat or leg press, a hip hinge such as a Romanian deadlift, a push, a pull and a loaded carry.
Work hard, but not to failure. Two to four sets of roughly 6–12 reps, finishing each set with a couple of reps left in reserve.
Progress gradually. Add a little weight, a rep or a set over time. Progression is what tells your body to hold on to muscle.
Keep moving on other days. Walking and low-to-moderate cardio support heart health and recovery.
Measure strength, not only weight. Track your lifts, your waist and how you move, not just the scale.
Making it work in real life
Weight loss rarely happens in a straight line, and training needs to adapt.
On low-appetite or nausea days, shorten the session and keep the intensity moderate rather than skipping entirely.
Eating less makes recovery harder. Protein and overall nutrition matter; a doctor or registered dietitian should set your targets.
Dubai heat adds risk. If you've had vomiting or diarrhoea, hydrate well, train indoors in summer and stop if you feel dizzy.
Your history matters. Old injuries, mobility limits and training experience all shape the right starting point.
This is where a generic plan from the internet falls short, and why individual coaching helps.
Frequently asked questions
What is Reta?
"Reta" is the common nickname for Retatrutide, an investigational once-weekly injection from Eli Lilly that activates GIP, GLP-1 and glucagon receptors.
Is Retatrutide approved in the UAE?
No. As of October 2026 it is not approved in the UAE or anywhere else. The Emirates Drug Establishment has warned residents not to buy it online.
How much weight do people lose on Retatrutide?
In the TRIUMPH-1 trial, participants on the highest dose lost an average of 28.3% of their body weight over 80 weeks. Results vary widely between individuals and trial populations.
Does Retatrutide cause muscle loss?
People on Retatrutide lose some lean mass, as with any major weight loss. One small study found the proportion was similar to other weight-loss drugs. Larger Phase 3 data are still awaited.
Is Retatrutide better than Mounjaro?
There is no head-to-head trial yet, so a direct comparison isn't possible. Retatrutide adds glucagon activity to the GIP and GLP-1 activity of tirzepatide (Mounjaro).
Can strength training prevent muscle loss on weight-loss medication?
It can't guarantee it, but resistance training is recommended by obesity experts as part of care during incretin-based treatment to help protect lean mass, strength and function.
Build Strength Alongside Your Weight-Loss Journey
Pull Gym offers structured 1-on-1 coaching in Dubai for adults who want to get stronger, fitter and more consistent. Every programme starts with an assessment of your goals, training history and constraints, then combines personalised strength training, conditioning and progress tracking that adjusts as you go.
Pull Gym is a fitness coaching service. We don't prescribe or supervise medication, so if you're using a weight-loss treatment, keep your doctor involved and we'll work around their guidance.
References
Eli Lilly. What to know about retatrutide. Updated September 2026. lilly.com
Eli Lilly. TRIUMPH-1 topline results. 21 May 2026. investor.lilly.com
Eli Lilly. TRIUMPH-2 and TRIUMPH-3 topline results. 23 July 2026. investor.lilly.com
TRIUMPH-1 trial record, NCT05929066. clinicaltrials.gov
Coskun T, et al. Effects of retatrutide on body composition in people with type 2 diabetes. Lancet Diabetes Endocrinol. 2025. doi:10.1016/S2213-8587(25)00092-0
EASO, EFAD and ECPO. Nutritional, functional and psychological considerations for obesity management medications in adults. 2026. easo.org
Khaleej Times. UAE cracks down on illegal weight-loss products. 25 July 2026. khaleejtimes.com
World Health Organization. Physical activity recommendations. who.int
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