In 2020, a drug that produced 10 percent weight loss was a serious achievement. By 2022, 15 percent was the reference point. By 2023, a phase 2 trial reported an average of roughly 24 percent at 48 weeks and had not yet plateaued.
The field is moving faster than clinical practice can absorb, and the ceiling everyone is now circling is the one where drugs and bariatric surgery produce the same number.
Why combinations rather than higher doses
You cannot solve obesity pharmacology by giving more GLP-1. Dose response flattens, and gastrointestinal side effects do not — push hard enough on a single receptor and you run out of tolerable dose before you run out of biology.
So the strategy shifted to recruiting additional pathways, each contributing a different part of the effect.
The three-receptor approach
Retatrutide activates GLP-1, GIP and glucagon receptors. Glucagon is the interesting addition and, at first glance, the counterintuitive one — it raises blood sugar, which is the opposite of what you want in diabetes. But glucagon also increases energy expenditure. In a molecule that simultaneously suppresses appetite through the other two receptors, the glucose effect is offset while the metabolic rate effect is retained.
That is a genuinely different mechanism from everything currently on the market: not just eating less, but spending more.
The amylin approach
CagriSema goes the other way — sideways rather than upward. Amylin is a hormone co-secreted with insulin that signals satiety through a pathway distinct from GLP-1. Pairing a long-acting amylin analogue with semaglutide targets two separate satiety systems rather than saturating one.
Every one of these drugs is an argument about which combination of hormones best imitates the thing a body does after bariatric surgery.
Where the numbers currently sit
~15%
Semaglutide 2.4 mg at 68 weeks
STEP 1, NEJM 2021
~21%
Tirzepatide 15 mg at 72 weeks
SURMOUNT-1, NEJM 2022
~24%
Retatrutide 12 mg at 48 weeks, phase 2
NEJM 2023
These are different trials with different populations and durations, so the progression is directional rather than a clean ranking. The retatrutide figure in particular comes from a phase 2 study — smaller, shorter, and historically prone to shrinking somewhat in phase 3.
The questions that get less attention than the headline
Body composition. At 24 percent total weight loss, the lean mass question stops being academic. We do not yet have good functional outcome data at these magnitudes, and the population most likely to be prescribed them includes a lot of people over sixty.
Nutritional adequacy. Bariatric surgery patients are followed for micronutrient deficiencies for life. Someone eating the equivalent volume because of a drug is running a similar risk with none of the monitoring infrastructure.
Who needs this much. A drug that produces 24 percent average loss is not obviously the right first choice for someone who needs to lose 12. More effective is not automatically better matched.
Durability. Surgery has thirty-year follow-up. The oldest of these drugs has been in widespread obesity use for a handful of years.
What I think actually happens next
Not a single winning drug — a stratified menu. A cheap oral agent for the large population who need modest, durable metabolic improvement. Mid-tier injectables for the mainstream. High-efficacy combinations reserved for severe obesity, where the risk-benefit calculation looks like the one we currently make for surgery.
Sorting people into that menu will require knowing how they actually responded to what they are on now — not a recollection, a record. The patient who plateaued at eight percent after a fair trial at a maximum tolerated dose is a candidate for the top tier. The patient who never got past 5 mg because of nausea is a different problem with a different answer, and telling the two apart a year later is impossible without dates. This is the unglamorous case for tracking in Zenday or anything like it: your own history is the evidence you will be triaged on.
That is a more boring future than the coverage suggests, and it is the one that actually resembles how medicine handles every other chronic condition once the options multiply.
The uncomfortable part is that America will almost certainly sort people into those tiers by insurance rather than by need.