GLP-1 Drugs: What Five Years of Data Actually Shows

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Five years ago, GLP-1 receptor agonists were diabetes drugs with a weight-loss side effect. Today they are the most consequential medications in cardiovascular medicine, and the most debated. The evidence has matured from promising mechanism to hard outcome data, and the picture that emerges is more nuanced than either the evangelists or the skeptics admit. The drugs clearly work. What the newest data asks is a harder question: work for how long, at what cost, and for whom?

The cardiovascular case rests on SELECT, the landmark semaglutide trial in people with overweight or obesity and established cardiovascular disease but no diabetes. Over a median follow-up of about four years, semaglutide cut major adverse cardiovascular events by 20 percent relative to placebo. That relative figure is the headline. The absolute figure is the fine print: roughly 1.5 to 2 percent fewer events over the study period, meaning about 50 to 65 people need treatment for years to prevent one event. Both numbers are true. The relative risk reduction tells you the drug is doing something real; the absolute reduction tells you how much work that something requires.

The weight data is more dramatic and more consistent. STEP 5 followed semaglutide for 104 weeks and recorded 15.2 percent mean weight loss, a figure that held rather than rebounded in the second year. SURMOUNT 4 tested tirzepatide, the dual GIP and GLP-1 agonist, and reached 25 percent weight loss at 88 weeks, the largest effect ever pharmacologically demonstrated in a randomized trial. Liraglutide, the older drug, sits near 8 percent. The class effect is real, the gradient between molecules is real, and the magnitude is unprecedented.

type: bar
title: Weight loss by drug at trial endpoint
x: Semaglutide, Tirzepatide, Liraglutide
Weight loss percent: 15.2, 25, 8

Then comes the finding that reframes everything. A 2026 real-world study in BMJ Medicine tracked patients who stopped GLP-1 therapy and found the cardiovascular benefit disappeared within 18 months of discontinuation. The protection was not a durable remodeling of risk; it was a rental. This matches the weight data, which shows most lost weight returning within a year of stopping. The body treats the drug as a temporary override, not a permanent fix, and readapts when it is removed.

flowchart TD
    A["Patient starts GLP-1 agonist"] --> B["Appetite and food noise drop"]
    B --> C["Weight falls, insulin sensitivity improves"]
    C --> D["Cardiovascular risk markers improve"]
    D --> E["Patient stops the drug"]
    E --> F["Appetite returns within weeks"]
    F --> G["Weight regains over 6 to 12 months"]
    G --> H["Cardiac benefit fades within 18 months"]
    H --> I["Decision: resume, switch, or accept"]

Discontinuation is not an edge case; it is the norm. Real-world studies consistently find 50 to 75 percent of patients stop within one year. The reasons are predictable: gastrointestinal side effects, cost, supply, and the simple difficulty of staying on a medication that changes your relationship with food. Nausea, vomiting, and diarrhea drive most early discontinuation. More concerning are the signals that do not resolve: depression and suicidal ideation warnings that regulators continue to monitor, and the loss of lean muscle mass that accompanies rapid weight loss, which can undermine metabolic health even as the scale moves in the right direction.

The pipeline is racing to answer these problems. Oral semaglutide, approved in December 2025 as the first oral Wegovy, removes the injection barrier for many patients. Triple agonists targeting GLP-1, GIP, and glucagon promise larger weight loss with potentially better body-composition profiles. CagriSema, the combination of semaglutide and the amylin analog cagrilintide, has shown weight loss approaching 25 percent in trials and may offer a path for patients who plateau on single agents.

GLP-1s and cardiovascular risk: what the latest evidence revealsPlays from YouTube when you press play

GLP-1 weight loss: side effects, cost and one-year updatePlays from YouTube when you press play

So what should a patient actually do? The honest answer is that the decision is no longer whether these drugs work. It is whether you are prepared to take them indefinitely, because the evidence says the benefits are contingent on continuation. For someone with obesity and cardiovascular disease, the calculus favors long-term use despite the cost and side effects, because the alternative is the risk the drug was shown to reduce. For someone using them for modest weight loss without cardiometabolic disease, the risk-benefit ratio is less favorable, and the 18-month evaporation finding should give pause.

The practical framework is boring but effective. Start low and titrate slowly to manage gastrointestinal side effects. Expect the first two months to be the hardest. Monitor mood, not just weight. Preserve protein intake and resistance training to protect muscle. Plan for the cost as a permanent line item, not a short-term investment. And have an explicit conversation with your prescriber about what happens if you stop, because the data says the answer is: most of it comes back.

The pendulum metaphor is apt. The drug swings the body toward a new equilibrium; stopping swings it back. The question the next five years of data will answer is whether any of the new agents can make the swing stick, or whether GLP-1s are, for now, a treatment you take for as long as you want the benefit to last.

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