Weight Loss Medications Beyond GLP-1: What Else Exists

GLP-1 medications have dominated recent conversation around medical weight loss, but they're one category among several with genuinely different mechanisms — some acting on appetite, one acting on fat digestion directly, each with its own profile of benefits, side effects, and situations where it may or may not be an appropriate fit.

Orlistat: Blocking Fat Absorption Rather Than Touching Appetite

Orlistat works through an entirely different mechanism than appetite-focused medications: it inhibits an enzyme called lipase that the digestive system needs to break down and absorb dietary fat. As a result, a portion of the fat consumed in a meal passes through the digestive system without being absorbed, rather than being taken in and stored. This mechanism comes with a distinctive, fat-intake-linked side effect profile — gastrointestinal symptoms that occur specifically in proportion to how much fat was eaten in a given meal, which in practice tends to reinforce lower-fat eating fairly directly, since higher-fat meals are more likely to trigger noticeable symptoms.

Naltrexone-Bupropion: A Combination Targeting Brain Reward Pathways

This combination pairs naltrexone, which blocks specific opioid receptors, with bupropion — the same medication discussed elsewhere as a smoking cessation aid, originally developed as an antidepressant. Together, they act on brain pathways involved in both appetite regulation and reward-driven eating specifically, a mechanism entirely distinct from the gut-hormone pathway GLP-1 medications work through. This combination illustrates the same pattern of medication repurposing seen elsewhere in medicine — components developed for other conditions found to have a genuinely useful additional application.

Phentermine-Topiramate: An Appetite Suppressant Combination

Phentermine is a stimulant-class appetite suppressant, and in this combination it's paired with topiramate, a medication originally developed for seizure disorders that independently has appetite-reducing effects of its own. Combining the two allows for effective appetite suppression at lower individual doses of each component than would be needed using either alone, which can reduce the side effect burden compared to a higher dose of a single agent.

A Brief History Lesson: Why Some Older Weight-Loss Medications Were Withdrawn

In the 1990s, a combination known as fen-phen (fenfluramine and phentermine) was widely prescribed for weight loss before fenfluramine was found to be associated with a serious heart valve complication in a meaningful number of patients, leading to its withdrawal from the market. This episode had a lasting effect on how weight-loss medications are developed and monitored — current medications in this category undergo considerably more rigorous long-term cardiovascular and safety monitoring, both before and after approval, specifically informed by lessons from that history. Rather than being a reason for concern about weight-loss medication generally, this history is part of why current oversight in this specific category is as thorough as it is.