There is a question we get asked almost every week with regards to weight loss: which one works better Mounxxxx or Wegxxx?
It is an understandable question, and there is an answer. In the first head to head trial comparing tirzepatide and semaglutide, tirzepatide (Mounxxxx) produced greater average weight loss compared with Wegxxx, with 20.2% versus 13.7% at 72 weeks.
But “produces more weight loss on average” and “is the right treatment for you” are two different statements. Conflating them is the single most common mistake we see patients make when they arrive having already decided what they want to be prescribed.
Here is how the decision actually gets made in a good consultation.
Average results describe populations, not people
A trial result is an average across several hundred people. Within that average sit patients who lost 30% of their body weight and patients who lost almost nothing. The headline number tells you what the medication tends to do. It tells you very little about what it will do for you.
Response varies substantially between individuals, and there is currently no reliable way to predict who will be a strong responder before starting. This is why we assess response at intervals rather than assuming the trial average will reproduce itself in every patient.
The medication you can stay on beats the one you can’t
Both of these medications are long term therapies. Weight is regained when they are stopped. This makes tolerability and sustainability far more important than most patients initially appreciate.
Both drugs commonly cause nausea, vomiting, diarrhoea and constipation, particularly during dose escalation. Some patients sail through. Others find one medication intolerable and do perfectly well on the other. There is no way to know in advance, it only becomes apparent once treatment starts.
This matters more than the percentage difference in trial results. A medication that produces a 20% average weight loss is worth nothing to a patient who stops it after six weeks because they cannot function. The gentler option that someone stays on for three years will always outperform the option that on average causes more weight loss that they abandoned.
Your other conditions often decide it
For many patients, weight is not the only thing being treated. It is frequently not even the most important thing.
These medications have been studied in specific conditions beyond obesity: cardiovascular disease, chronic kidney disease, obstructive sleep apnoea, heart failure with preserved ejection fraction and fatty liver disease. The evidence base is not identical between them. Each has trial data in some conditions and not others.
If you have a specific comorbidity, the medication with completed trial evidence in that condition is usually the correct starting point, even if it is not the one with the larger headline weight loss figure. Treating the condition you actually have beats optimising a number on a scale.
Contraindications also override preference entirely. Pregnancy, a personal or family history of medullary thyroid carcinoma or MEN2 syndrome, previous pancreatitis, and severe gastroparesis all change or close off options regardless of what anyone would prefer to prescribe.
Faster is not automatically better
Rapid weight loss carries costs, like with Wegxxx. More of the weight lost comes from lean tissue rather than fat. Gallstone risk rises. Gastrointestinal side effects are more pronounced. For older patients, or patients who are already low on muscle mass, aggressive loss can leave them functionally weaker even as the scale improves.
Importantly, rate of loss is largely a dosing decision, not a drug choice decision. Both medications are titrated upward over months, and both can be escalated more slowly, or held at a lower dose, when that suits the patient. Choosing a slower path does not require choosing a different molecule.
For a 35 year old with severe obesity and worsening sleep apnoea, faster Wegxxx is genuinely better. For a 68 year old with modest excess weight and declining grip strength, it is not and Mounxxxx might be better. Same clinic, same medications, opposite answers.
What we protect regardless of which one you’re on
Some of the weight lost on any weight loss intervention is lean tissue: muscle, bone, connective tissue and organ mass. This is true of dieting, bariatric surgery, and both of these medication classes. It matters for strength, resting metabolic rate, fall risk, and how quickly weight returns if treatment stops.
It is also substantially controllable, and the levers are the same whichever medication you take:
- Protein intake of roughly 1.2–1.6 g per kg body weight daily, adjusted for kidney function. This is genuinely difficult on appetite-suppressing medication and requires planning rather than willpower.
- Resistance training at least twice weekly. This is the most effective single intervention available for preserving lean mass during weight loss.
- Body composition measurement at baseline and at intervals, so you know whether the weight coming off is the weight you wanted to lose. The scale alone cannot tell you this.
- Sensible titration pace, adjusted to how you are tolerating treatment rather than to how quickly you would like results.
Patients who do these things hold onto substantially more lean tissue. Patients who do not lose more of it, on either medication.
What a proper consultation covers
Before prescribing, we work through: your full medical history and current medications; what you have tried previously and how it went; your other conditions and which of them a given medication has evidence for; contraindications; your realistic capacity for the protein and training side of the plan; and cost and supply over a multi year horizon rather than the first three months.
Then we choose. Sometimes that means the medication with the larger average effect. Frequently it does not.
The bottom line
Both of these medications are genuinely effective, and both are safe in appropriately selected patients. The question worth asking is not “which causes more weight loss” but “which is right for me, at what dose, alongside what else” and that is a question that requires your history, your bloods, and a conversation.