At least half a million Australians are taking weight-loss drugs such as Ozempic and Mounjaro every month, with popularity continuing to increase despite a shortage of the drugs.
Nutrition and dietetics professor Clare Collins believes there is a "blind spot" in current research on the side-effects to these medications, and says nutritional intake is often overlooked in trials.
Little is known about whether people using these drugs are receiving adequate nutrition, she warns.
"We're trying to ring a bell really loudly," Professor Collins told AAP.
Research released on Tuesday by the Hunter Medical Research Institute and the University of Newcastle found that, out of 41 randomised controlled trials on popular GLP-1/GIP medications over the past 17 years, only two studies involving adults measured or reported dietary intake, and one of those remains unpublished.
GLP-1/GIP are receptor agonists that suppress appetite and reduce overall food intake, which many weight-loss medications are designed to mimic.
"These drugs are very expensive, they're very powerful and they work. But the nutritional status is not on the radar and (it's) putting people at long-term risk of nutrient deficiencies and or malnutrition," Prof Collins said.
While people using weight-loss medications may appear healthier due to reduced body weight, inadequate nutrition can increase the risk of cardiovascular disease, metabolic complications, inflammation and long-term chronic conditions, including some cancers.
There have also been reports of thiamine (vitamin B) deficiencies and protein malnutrition, which, if not addressed, can progress to a permanent neurological condition, Prof Collins warned.
"These medications offer enormous potential, but to truly support long-term health, we need to understand not just how much weight people lose, but how well they are nourished," she said.
"There is already starting to be case reports of nutrient deficiencies, it just seems that it's kind of like a blind spot."
Researchers believe more studies are needed to address nutrition-related side effects.
"It's not talked about," Prof Collins says.
"Yet many of the side effects that people experience can also be ameliorated or supported by nutrition. It's kind of crazy that this is missed."
The report recommends that future studies monitor diet and changes in diet quality, stating that without this information it is difficult to evaluate effectiveness and safety from a nutritional perspective.
