Popular medications such as semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro), and liraglutide (Saxenda) are transforming the treatment landscape for obesity and type 2 diabetes. These GLP-1 and GIP receptor agonists, backed by substantial clinical evidence, have demonstrated significant weight loss, enhanced blood glucose control, and improved metabolic health. Their use is on the rise globally.
However, a recent systematic review has brought attention to a critical oversight in current research. While the focus has been heavily on weight and health outcomes, there is scant information regarding the changes these medications induce in dietary habits, nutrient intake, and whether the weight loss achieved supports long-term nutrition-related health and wellbeing.
Unveiling the Gaps in Current Research
The review scrutinized randomized controlled trials of GLP-1 and GIP receptor agonists conducted over the past 17 years. Despite involving over 50,000 participants across 41 trials, only two studies assessed or reported dietary intake data or changes in diet as an outcome.
“These medications work, there’s no question about that,” said Clare Collins, Laureate Professor of Nutrition and Dietetics at the University of Newcastle and a HMRI Nutrition & Metabolic Health researcher.
Professor Collins emphasized, “But a reduction in body weight does not automatically mean the person is well nourished or healthy. Nutrition plays a critical role in health, and right now it’s largely missing from the evidence. With case reports of thiamine deficiency and protein malnutrition, we need to ensure we are not throwing the baby out with the bath water.”
Weight-Loss: Not the Whole Story
GLP-1 and GIP receptor agonists are known to suppress appetite and reduce overall food intake, contributing to weight loss. However, this raises important questions about diet quality, adequacy of nutrient intakes, and whether individuals are meeting their nutritional needs within lower energy intakes.
The review found that only two trials involving adults reported measuring dietary intake, and one of these studies remains unpublished. Both reported a reduction in total energy intakes, with an altered macronutrient distribution in the medication plus diet group, although it was not significantly different from medication alone. The methods used to assess diet were rated as “poor” or “acceptable,” limiting confidence in these findings.
“When people are eating less, the quality of what they eat matters even more,” Professor Collins said. “If someone loses weight but their diet lacks adequate protein, fibre, vitamins, or minerals, that has major concerns for their long-term muscle mass, bone health, brain health, gut health, as well as skin integrity and overall wellbeing.”
Health Beyond the Scales
Weight is an easily measured outcome, which partly explains its dominance in clinical trials. However, these medications and diet quality influence far more than body weight alone, including cardiovascular health, metabolic risk, inflammation, and long-term chronic disease outcomes, such as the risk of some cancers.
Without robust dietary data, clinicians and researchers cannot fully understand the broader health effects of these medications. They are unable to tailor advice for the use of these medications, particularly in long-term maintenance, nor provide evidence-based guidance to support patients using them.
The review also highlights a broader issue in obesity and diabetes research, where diet is often treated as a secondary consideration rather than a core component of metabolic health.
“If we only measure weight and blood sugar, we’re missing a big part of the picture,” Professor Collins said. “Diet quality, food patterns, and nutrient intake all contribute to health. They should be measured with the same rigour as other clinical outcomes.”
A Call for Comprehensive Research
The authors stress that their findings should not be interpreted as criticism of GLP-1 and GIP medications, but rather as a call for more comprehensive research. As the use of these drugs continues to grow, understanding how they interact with eating behaviors and nutrition will be essential to maximizing benefits and minimizing unintended risks.
The review calls for future clinical trials to include validated dietary assessment methods and to report dietary outcomes transparently alongside weight, health, and glycaemic measures.
“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,” Professor Collins concluded.
This article was originally published by Hunter Medical Research Institute.
