will new weight loss drugs really bring an end to obesity?
5 minute read
when people inject themselves with ozempic, or mounjaro, their bodies make more of the hormones that regulate hunger and feelings of satiety.
joel saget/afp via getty images
the weekly injection has helped people drop the kind of weight once only achieved by surgically reconfiguring the gut. it makes people obsess less about food and, according to headlines, is poised to turn its trendy rival, ozempic, into yesterday’s news.
the drug, mounjaro, already approved in canada and the u.s. for type 2 diabetes, is expected to soon be approved for weight loss in the u.s. after it was granted a speedy review by the food and drug administration.
published results to date suggest mounjaro offers a greater reduction in weight than ozempic, or ozempic’s tweaked sister drug, wegovy.
taken together, this new era of aoms — anti-obesity meds — could mean an “end” to obesity, according to the economist and other media outlets.
feverish hyperbole? yes and no, say those working in the field.
globally, more than 650 million adults are obese, and the dark history of weight-loss drugs suggests it would be prudent to dial down the hype. the costs could also put the drugs out of reach of the people who most need them. however, according to a review in the lancet, monjaro and other anti-obesity medications on the horizon “promise to revolutionize the way we will be treating obesity in the near future.”
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“you can think of a world where we don’t have obesity anymore, or it’s very uncommon,” dr. nadia khan, a professor of medicine at the university of british columbia recently told an audience of doctors, residents and medical students.
the obesity-drug “gold rush,” reuters reports, is expected to reach us$50 billion annually by 2030. already, frenzied demand for ozempic and wegovy has led to widespread shortages. in november, health canada approved mounjaro for people with type 2 diabetes, though doctors can prescribe it “off label,” meaning for uses other than those formally endorsed by the drug regulator. the drug still hasn’t launched in canada. its maker, eli lilly, is ramping up manufacturing capacity “to meet the extraordinary demand for the product, and commercial launch in canada will only happen once we have sufficient supply to meet the needs of canadian patients,” lilly said in an email to the national post.
“mounjaro has not been submitted for canadian regulatory approval for weight management, and although it may be submitted for this indication in the future we are not permitted to speak about the product, off-label,” the company said.
ozempic also hasn’t been formally approved for weight loss in canada, though it hardly seems to matter: more than 3.5 million prescriptions worth nearly $1.2 billion were filled by canadian retail drugstores last year, up from just over 81,000 orders in 2018, according to iqvia compuscript.
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“not since botox, and before that viagra, has a drug brand become so well-known so quickly,” matthew schneier wrote in the cut.
but ozempic’s reign, the atlantic’s yasmin tayag wrote this week, “might be short-lived.”
ozempic and wegovy, which both contain the same active ingredient, semaglutide, mimic a gut hormone called glucagon-like petitde-1, or glp-1, that works on the appetite centre of the brain to control hunger.
but mounjaro, chemical name tirzepatide, targets a second hormone, gip, that also works to decrease food intake.
in a lilly-sponsored study published last year, people on mounjaro lost, on average, 19.5 to 21 per cent of their body weight over 72 weeks, depending on the dosage, “an unusually substantial degree of weight reduction” for a weight-loss drug, the authors wrote, and one that’s approaching the numbers seen with bariatric surgery. more than half of those on the highest doses had a reduced body weight of 20 per cent or more.
in a 2021 study of wegovy, which contains a slightly higher dose of semaglutide than ozempic, people lost, on average, 15 per cent of their weight at week 68.
the new drugs come with side effects, most commonly nausea, diarrhea and other gastro-intestinal complaints, and they’re most likely life-long, “forever” drugs. with ozempic, once off, people regained two-thirds of their lost weight within a year.
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in the u.k., concerns have been raised about the “medicalization” of obesity and well-orchestrated marketing campaigns by drug manufacturers. obesity specialist dr. arya sharma, a professor emeritus of medicine at the university of alberta, has blogged about the potential magnitude “of misuse and abuse of these medications by folks who clearly do not have a medical need to lose weight.”
but while they’re not medical miracles, the new drugs do seem “vastly better” than what came before them, wrote pharmacist and obesity health-care professional ted kyle on his blog, conscienhealth.
the drugs appear to stop ever-present, obsessive thoughts about food, and get at the deeper question as to why people eat too much. there’s a paradigm shift away from focusing on “the willpower issue” to the gut-brain connection, said khan, a general internist. “this is probably our best target.”
the brain’s hypothalamus controls appetite regulation — how full or hungry we feel. the mesolimbic system controls wanting and liking. we can’t alter those parts of the brain, khan said. but the hypothalamus, especially, receives signals from the stomach, intestine and fat tissue.
when food enters the stomach, ghrelin, the hunger hormone, gets suppressed, and glp-1 and gip are released from the intestine. those gut-secreted hormones signal to the brain “we’re full.”
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when people inject themselves with ozempic, or mounjaro, their bodies make more of the hormones that regulate hunger and feelings of satiety.
“you could imagine, in some people they may require a lot more of those signals to override a brain that’s hardwired to feel hungry more, to feel less full,” khan said. “we’re able to now manufacture something that everybody is producing, and we’re actually able to keep it in the brain and the system a lot longer.”
the drugs also act on the gut to slow gastric emptying, or how fast food travels through the digestive tract. mounjaro also appears to lead to greater reductions in total body fat mass than ozempic.
the benefits for both drugs for obesity appear to outweigh the risks, khan said. but the field has a sorry history. it wasn’t until “miracle” drugs like the disastrous fen-phen regimen were widely prescribed that signals of severe side effects, including heart valve damage, stroke and cardiovascular death, emerged.
long-term affordability remains very much in the air — ozempic costs $250 a month for the most common dose, and $500 a month for a higher dose. and while many people who don’t need to lose weight and just want to be skinnier seem “particularly enthralled” with the new drugs, schneier wrote, it’s not clear what the risks might be for people who aren’t actually living with obesity, khan said.
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