Obesity management update: semaglutide plateau, tirzepatide switch, and the coming 7.2 mg dose

Samantha Hockey — obesity management update

Endocrinologist; precision-medicine interest in metabolic disease and diabetes. Disclosures: work with companies that make obesity medicines available in Australia. Current president of the National Association of Clinical Obesity Services (NACOS). Otter heard “Hockey” — we keep that byline (if you suspect Hocking, Otter still heard Hockey).

Host

Healthed seminar host (speaker 0 intro; main talk is speaker 1).

Clinical case: Monica

Monica is 62, works as a sales manager, and lives with obesity: BMI 33.7, waist circumference 92 cm. She was diagnosed with pre-diabetes two years ago and takes metformin 500 mg daily; HbA1c is 6.1%. She is also treated for hypertension and dyslipidaemia — a metabolic syndrome phenotype — and has painful knee osteoarthritis that limits her ability to travel.

She started semaglutide (Wegovy) 12 months ago, escalated to 2.4 mg weekly, lost 10.2 kg (~10% body weight), and feels she has reached a plateau. She still has pre-diabetes and knee pain, plans to retire and travel in the next few years, and wants a better health outcome — not just a nicer number on the scales.

Is a weight-loss plateau surprising?

No. In a two-year trial of semaglutide 2.4 mg, most weight is lost in the first 6–9 months; beyond about a year people reach a plateau. With modern obesity medicines the plateau is typically flat — no rebound while treatment continues out to two years.

Categorical weight loss at week 68 (on-treatment as intended): the vast majority respond if response means ≥5% loss — about 92%. Higher thresholds are not universal: about half achieve >15%; only about one in three achieve ≥20%. A waterfall plot of individual responses (72-week study) shows biological variability from “super-responders” to rare non-responders — not a moral story about effort.

Early weight loss predicts later response

We still lack precision tools at baseline to pick super-responders vs non-responders. What we do know: early weight loss predicts longer-term weight loss. Little response in the first 3–6 months usually means a modest final result. Monica already has ~10% — reasonable — but she is not happy with her remaining health goals.

Weight loss vs health gain

Managing obesity is becoming more nuanced: kilograms matter when they buy health gain for the person in front of you.

• Pre-diabetes → prevent type 2 diabetes: as little as 5–7% body-weight reduction helps (long-standing prevention-trial evidence).
• Type 2 diabetes remission: often needs higher loss, more like 10–15% (DiRECT; bariatric surgery data).
• Sleep apnoea and MASLD with fibrosis: often need around ≥15% for meaningful regression of fibrosis / disease modification.
• Knee osteoarthritis: strong association with overweight/obesity (~2.5–5× risk); pain and function scores improve in a dose-response fashion with more weight loss.

Switching to tirzepatide

She is already on 2.4 mg and plateaued. Is switching an option? Cross-trial caution applies (STEP 1 vs SURMOUNT-1 are different populations), but mean losses on tirzepatide were higher: roughly 15% (5 mg), 19.5% (10 mg ITT), 20.9% (15 mg ITT; ~22.5% if continued on 15 mg as intended) versus ~17% often cited for semaglutide 2.4 mg in completers.

A head-to-head maximum-tolerated-dose comparison (semaglutide 1.7 or 2.4 mg vs tirzepatide 10 or 15 mg): about 13.7% vs 20.2% mean loss (ITT) — statistically and clinically more on tirzepatide. Categorical ≥25% loss: about one in three on tirzepatide 10/15 — roughly double the rate on semaglutide 1.7/2.4.

Step Up: semaglutide 7.2 mg

If she is reluctant to change — she has finished escalation, GI effects settled, and she tolerates 2.4 mg well — a higher dose of semaglutide is coming: 7.2 mg weekly (hoped to arrive in Australia soon). The Step Up trial escalated as usual to 2.4 mg, then made a big step to 7.2 mg (triple the dose; no intermediate increments), followed participants to about a year, plus lifestyle counselling (≈500 kcal/day deficit; 150 min activity/week). Population: obesity without type 2 diabetes (BMI ≥30).

Rough randomisation scale: ~1000 on 7.2 mg, ~200 on 2.4 mg, ~200 placebo. About 90% completed on the lower dose vs about 75% on 7.2 mg — some struggle at the high dose; if so, drop back to the highest tolerated dose (2.4 or even 1.7 mg) rather than stopping entirely.

Categorical ≥25% loss: about one in three on 7.2 mg vs about one in six on 2.4 mg — roughly double the chance of “disease-modifying” loss magnitudes.

Body composition and function

MRI body-composition sub-analysis (more accurate for muscle than DEXA): the vast majority of loss is fat mass, with visceral fat volume falling most — desirable in metabolic syndrome. Overall, about 85% fat / 15% lean. Sit-to-stand function improved similarly in 7.2, 2.4, and placebo arms — reassuring against “more frail / sarcopenia” fears despite some lean loss (inevitable with any substantial weight loss). Among those with pre-diabetes at baseline, about 83% reverted to normoglycaemia on 7.2 mg vs about 73.8% on 2.4 mg.

Side effects, including dysaesthesia

Triple the dose does not mean triple the adverse events. Overall AEs were similar across placebo, 2.4, and 7.2. Permanent discontinuation for AEs: about 5.4% on 7.2 vs about 4% placebo; GI-driven stops about 3.3% vs 2% on 2.4. GI events were numerically a bit higher on 7.2 — not triple.

Dysaesthesia (unusual skin sensations / discomfort) is a recognised class effect of GLP-1 and GIP/GLP-1 agonists. It affected about one in five people stepped up to 7.2 mg — related to the jump from 2.4 — usually mild, improves with time; only about 1.7% permanently discontinued for it. Warn before escalating: “You may notice strange skin sensations; usually mild and settles.” Forewarning supports adherence. Gallbladder events track weight loss; pancreatitis rates were extremely low in the trial; CV disorders were numerically lower on 7.2 in the slides shown.

What this means in clinic

Increasing dose can increase appetite suppression and weight reduction — we already saw that across tirzepatide 5 / 10 / 15 mg. Soon, 7.2 mg Wegovy offers another option for people who have not met health goals on 2.4 mg, with a safety/AE profile broadly familiar to 2.4 mg. Use higher intensity for health gain (OA symptoms, glycaemia, sleep apnoea, liver fibrosis), not endless scale chasing. Greater weight loss also tracks greater waist, BP, and glucose improvements in the data alluded to.

Speaker plug (brief): NACOS — National Association of Clinical Obesity Services — free membership and free education; advocacy for PBS access and wraparound care. Free clinical masterclass in obesity management, Brisbane, Saturday 24 October (Boco/Bogo Hotel as heard) — QR registration on the day slides.

Take-home messages for clinic

1. Plateaus on semaglutide 2.4 mg after ~6–12 months are expected; continued Rx usually maintains a flat line.
2. Early response (3–6 months) predicts longer-term loss; biological variability is large.
3. Match further intensity to health goals (e.g. knee OA, pre-diabetes, sleep apnoea, MASLD fibrosis) — not vanity kilograms.
4. Switching to tirzepatide can add clinically meaningful loss (head-to-head ~20% vs ~14%).
5. Semaglutide 7.2 mg (Step Up) ≈20.7% mean; ~double the ≥25% responders vs 2.4; drop back if not tolerated.
6. Composition: mostly fat (esp. visceral); function not worse; warn about dysaesthesia on the 2.4→7.2 step.
7. Treat obesity for health gain; consider NACOS education / advocacy resources.

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