Some people don’t respond

A glucagon-like peptide 1 drug is supposed to make the brain feel full sooner and the stomach empty more slowly, but a noticeable slice of patients lose far less weight than the ads and headlines suggest. In the biggest semaglutide obesity trial, 86.4% of patients lost at least 5% of body weight by week 68, which means 13.6% did not hit that basic benchmark. (nejm.org) That 5% line is not arbitrary. Obesity trials and recent clinical reviews use 5% total body-weight loss as the minimum cutoff for saying a treatment is producing a clinically meaningful effect, even though many patients hope for 15% or 20%. (thelancet.com) Semaglutide is the ingredient in Wegovy, and it copies a gut hormone called glucagon-like peptide 1, which is released after eating. The drug turns up satiety signals and usually reduces calorie intake, but biology is messy enough that the same dose does not produce the same result in every body. (nature.com) Tirzepatide, sold as Zepbound for obesity, adds a second hormone pathway called glucose-dependent insulinotropic polypeptide on top of glucagon-like peptide 1. In the SURMOUNT-1 trial, 85.1% to 90.9% of patients on tirzepatide reached at least 5% weight loss at 72 weeks, so even with a stronger average effect, a minority still did not cross that line. (nejm.org) Doctors use the term “non-responder” for those patients, but that label can hide several different stories. One patient may stop early because nausea or vomiting makes eating miserable, another may miss doses because insurance coverage breaks, and another may take the drug consistently and still see only a small change on the scale. (nejm.org) Type 2 diabetes can also change the picture. Trials and reviews have repeatedly found that people with obesity and diabetes tend to lose less weight on these medicines than people with obesity alone, even when blood sugar improves. (nature.com) Time matters too, because these drugs are titrated slowly over months to reduce stomach side effects. A person who spends weeks at lower doses, skips injections, or stops before the maintenance dose may look like the drug “failed” when the real issue is that the full treatment course never happened. (nejm.org) The newer medical message is not that the drugs are weak. The newer message is that averages can be huge while individual responses still spread across a wide range, from dramatic losses of 15% or more to almost no meaningful change at all. (nejm.org 1) (nejm.org 2) That is why obesity specialists increasingly talk about these injections the way oncologists talk about cancer drugs: as treatments that work very well for many patients, somewhat for others, and poorly for some. The practical question after a few months is not whether the drug is famous, but whether this specific patient is actually losing weight, tolerating the dose, and able to stay on it. (thelancet.com)