Weight-loss medications don’t have a proud past. Beginning in the 1940s, “rainbow diet pills” containing amphetamines and diuretics were marketed to American women with the air of a breakfast cereal. Let’s fast-forward to the 1990s and the emergence of fen-phen, a combination medication that caused significant weight loss as well as severe lung and heart damage in enough patients to lead to widespread legal action and an FDA withdrawal.
Over the course of several decades, the pattern remained largely consistent: a medication shows promise, becomes widely prescribed, and then reveals a side effect profile that can range from problematic to lethal. By the time the 2010s rolled around, the field of treating obesity had earned a quiet reputation as a place where hope dies.
| Field | Details |
|---|---|
| Drug Class | GLP-1 Receptor Agonists (Glucagon-Like Peptide-1) |
| Key Drugs | Semaglutide (Ozempic/Wegovy), Liraglutide (Victoza), Tirzepatide (Mounjaro/Zepbound) |
| Original Purpose | Type 2 diabetes treatment |
| First GLP-1 Drug Approved | Exenatide (Byetta) — FDA approved 2005, derived from Gila monster venom peptide |
| Wegovy Approval (Obesity) | FDA approved semaglutide for obesity management — 2021 |
| Weight Loss in Pivotal Trial | ~15% body weight loss (semaglutide); up to 21% (tirzepatide) |
| Cardiovascular Benefit | 20% lower risk of fatal/nonfatal heart attacks and strokes (17,000-person trial) |
| Named Science Breakthrough | AAAS Science magazine — Breakthrough of the Year 2023 |
| Market Impact | Novo Nordisk’s market value exceeds GDP of Denmark |
| Monthly Cost (U.S.) | ~$1,000+ without insurance |
| Manufacturer | Novo Nordisk (semaglutide); Eli Lilly (tirzepatide) |
| Reference Website | Science AAAS – GLP-1 Breakthrough of the Year |
This makes the events that have transpired since 2021 truly startling to observe. Built around the gut hormone glucagon-like peptide-1, or GLP-1, a class of medications initially created to treat type 2 diabetes has produced weight loss results in clinical trials that no prior obesity treatment had come close to matching, with a side effect profile that most patients and doctors find tolerable.
The medications function by imitating GLP-1, a hormone that the intestine naturally releases after eating. This hormone slows digestion, controls blood sugar, and tells the brain to decrease appetite. Many patients report a quieting of what researchers have begun to refer to as “food noise”—the enduring, nearly involuntary mental pull toward eating that obese people frequently find exhausting to resist. The medical community has long suggested that the issue may be biological rather than motivational. The first compelling pharmaceutical argument in that direction is these medications.
The history of GLP-1 research is the kind of information that is often forgotten once a medication becomes widely used in society, but it is important to understand. Exenatide was the first GLP-1 medication approved by the FDA in 2005. Its active ingredient came from a peptide found in the venom of the Gila monster, a large, slow-moving lizard native to the American Southwest, rather than from human biology. Researchers discovered that the Gila monster peptide and human GLP-1 shared structural similarities that made it pharmacologically beneficial.
Its appeal was limited because it required daily injections. The subsequent version from Novo Nordisk, liraglutide, needed the same frequency and was based on human GLP-1. Semaglutide—weekly injections, significantly better outcomes, and a pivotal trial that revealed patients lost an average of 15% of their body weight over about 16 months—was the real game-changer. In the field, that figure was unheard of. Comedian Jimmy Kimmel made reference to this cultural moment from the 2023 Academy Awards stage, joking about whether the room was on it. The medication was approved for the treatment of obesity as Wegovy, and its diabetes version, Ozempic, was already widely prescribed.
The discussion took a more somber turn after the initial weight loss trials due to cardiovascular data. Semaglutide produced a 20 percent lower risk of fatal or nonfatal heart attacks and strokes compared to placebo in a trial of 17,000 individuals with excess weight and pre-existing cardiovascular disease. This finding was published in the New England Journal of Medicine and is generally regarded as the most convincing evidence to date that these medications do more than just lower scale numbers.
Semaglutide users were able to walk an extra 20 meters in a six-minute test and had almost twice the improvement on standard heart function measures, according to a different study involving patients with obesity and heart failure. This is a significant expansion of proven benefit for a medication that began its life controlling blood sugar in diabetic patients.
It’s difficult to ignore how rapidly the research community’s goals for GLP-1 medications have expanded beyond metabolic disorders. Semaglutide is presently being tested for addiction, Parkinson’s disease, and Alzheimer’s disease. Patients taking the medication for diabetes and obesity started to spontaneously report less desire for alcohol and cigarettes, which led to the somewhat accidental emergence of the addiction angle.
Researchers hypothesize that the medications attach to brain receptors that control desire in general, not just appetite. GLP-1 receptors may play a role in reward-seeking behavior in ways that the early 2000s researchers studying Gila monster venom could not have predicted. The degree to which the field’s confidence in these medications has increased is demonstrated by the fact that these possibilities are being considered in peer-reviewed trials rather than being written off as anecdotal.
However, the reluctance is genuine and worthwhile. A significant percentage of patients discontinue treatment before experiencing the full benefits due to nausea and gastrointestinal distress. In 2023, Ozempic’s label was updated by U.S. regulators to reflect a possible risk of intestinal obstruction, and a Canadian study found increased risks of both pancreatitis and that complication.
The data on weight gain is alarming: patients had regained about two-thirds of the weight they had lost a year after stopping semaglutide. This is not surprising to the researchers who describe obesity as a chronic illness that needs constant care, much like diabetes or hypertension. However, the implication is that many patients would have to take the medication indefinitely, which would cost more than $1,000 a month in the US. This raises equity concerns that the current insurance and healthcare system is ill-prepared to address.
Now approved for both diabetes and obesity, Eli Lilly’s tirzepatide has been shown in large trials to help patients lose up to 21 percent of their body weight, surpassing even the results of semaglutide. Instead of using just one hormonal pathway, it uses two. Even though the current versions are impressive, the next generation of drugs that target three hormonal pathways is already under development, suggesting that by the time this story is fully told, the current versions may seem like an early chapter.
The fact that Novo Nordisk’s market valuation exceeds the GDP of Denmark, the company’s home nation, highlights the significant economic impact of these compounds’ ongoing success. As the trials continue to mount, it is important to consider whether this financial intensity is pushing research in the right directions or whether it is putting pressure on researchers to minimize inconvenient findings.
