Is Percent Weight Loss the Right Obesity Treatment Target?

The focus of obesity-management interventions should shift from percentage weight-loss targets to patient-oriented parameters such as enhancing quality of life (QoL) and function, research to be presented at the European Congress on Obesity suggests.

“We were surprised to find that the long-held treatment target of 5% total weight loss that has been used to determine clinically significant weight loss was derived only from a few large studies,” Sanjeev Sockalingam, MD, of Obesity Canada and the Centre for Addiction and Mental Health in Toronto, Ontario, Canada, told Medscape Medical News.

“We should be moving away from a simplistic percent weight loss as the sole obesity treatment target in research, despite its ease of use and measurement, and move towards more comprehensive health measures,” he said. “Codesign with patients and healthcare providers is critical to developing comprehensive treatment targets that are based on research and can be integrated into practice.”

Lifestyle, Function, QoL

Researchers performed a literature review through July 29, 2024. Inclusion criteria were peer-reviewed studies in adults with obesity aged 18 years or older, focusing on weight reduction as a percentage of body weight. The review aimed to synthesize evidence on percentage weight-based targets in obesity interventions and discuss their correlation with health outcomes.

“We are in the process of conducting an international collaborative project to redefine patient-centered treatment targets for patients living with obesity that go beyond traditional weight-loss outcomes,” Sockalingam noted. “This scoping review was an important first step.”

The search yielded 30 studies, primarily randomized, controlled trials and quasi-experimental studies, published between 1992 and 2024. The studies mainly targeted 3%-10% weight loss, with a few aiming for higher thresholds. The researchers found a “notable discrepancy” between targeted and achieved weight loss, highlighting a frequent failure in reaching set goals.

There was heterogeneity across the included studies. A third did not provide post-study results for body mass index or weight change. The rationale for selecting specific weight-loss targets varied from disease-specific outcomes to improving QoL. Few studies were powered to look at differences beyond weight change outcomes.

The scoping review enabled the authors to look at where the frequent target of 5% weight loss came from; they found that the original 5% weight-loss goal was set from a small number of well-resourced studies in which the 5% target was associated with health benefits.

The authors of the review did not look quantitatively at how often people hit this 5% weight-loss target. However, they did observe that in some of the studies, only one third of patients achieved a weight-loss target of 10% or more. And because most of the studies looked at populations where people were not only living with obesity but also had myriad obesity-related conditions, they saw there was often an improvement in health outcomes with interventions such as nutrition, exercise and lifestyle, regardless of the weight-loss outcome.

Therefore, they concluded, “Obesity management interventions would benefit from shifting focus towards more comprehensive, patient-focused parameters, such as improvement of obesity-related complications, enhancing quality of life and overall physical and social functioning. This approach could provide more meaningful measures of success beyond mere weight reduction.”

The next step for the international collaboration is to create a framework for identifying and selecting treatment targets for obesity that involve patients’ preferences and treatment goals, in addition to the literature, Sockalingam said.

Changes to treatment targets “would not compromise rigor and the use of objective measures,” he added. Many of the collaborative team members participated in the development of outcome measures for the International Consortium for Health Outcomes, which include suggested objective and self-report measures, both of which are “critical” to comprehensive obesity assessment and development of treatment targets/goals.

‘Not Ideal, But Simple’

Commenting on the study for Medscape Medical News, Bariatric Surgeon Mir Ali, MD, medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, California, said that for the most part, he agreed with the study findings.

“Weight loss is so variable from person to person that assigning a specific target is sometimes not realistic,” he affirmed. “That being said, there has to be some way to monitor a patient’s progress.” 

The amount of weight loss is “clearly not ideal” for monitoring progress, but it is simple, he said. In contrast, “monitoring the change in health conditions is often difficult and changes occur slowly.”

Importantly, he noted, “the study does not provide simple, realistic alternatives to measuring a patient’s progress. Future studies comparing different monitoring methods would be helpful.”

This research was led by Obesity Canada and financially supported through an investigator-initiated grant in aid from Novo Nordisk, Eli Lilly Canada, Boehringer Ingelheim, and Amgen.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.