Obesity expert says body composition testing can guide GLP-1 use
Health guidance emphasizes individual risk assessment and body metrics before considering GLP-1 medications; WHO advises limited, targeted use for obesity care.
An obesity medicine specialist says the decision whether GLP-1 medications are appropriate should start with body composition testing rather than simply weighing on the scale. In an interview with Fox News Digital, Dr. Rocio Salas-Whalen, M.D., author of Weightless, said the best way to decide if a GLP-1 is right for a patient is to assess body composition and health history before prescribing. The conversation comes as GLP-1–based therapies have become more widespread and accessible, prompting some experts to suggest broad candidacy while others caution that treatment should hinge on individual health status and risks.
Body composition testing measures three markers of health: skeletal muscle mass, body fat percentage, and visceral fat. Visceral fat surrounds internal organs and is pro-inflammatory, which can increase insulin resistance and hyperinsulinemia. Salas-Whalen described a typical screening approach: “I perform a body composition on everybody who walks through the door. I want to see your visceral fat, which is the fat that surrounds your internal organs. It's pro-inflammatory fat, which increases insulin resistance [and] hyperinsulinemia (a condition where there is too much insulin in the blood relative to what the body needs).” The screens also reveal a person’s percentage of body fat, the portion of weight that is fat.
Salas-Whalen noted that the target body fat percentage should be around 28% or below for women and 20% or lower for men. Skeletal muscle mass is another important marker for health, she explained. “Muscle is an anti-inflammatory organ,” she said. “It also decreases insulin resistance … [and] consumes 80% of your glucose.” The muscle mass you carry is partly the result of both diet and exercise, and it influences how effectively your body handles glucose and insulin, which can affect the success of GLP-1 therapy.
The goal in weight management, she added, is not simply to lose weight on the scale but to achieve favorable body re-composition: more lean mass and less visceral fat. “If you have a good body composition, rest assured that you're getting all the benefits that somebody on a GLP-1 would,” she said. “It’s not safe to use a medication that you don't have a requirement for.” She emphasized that every patient’s journey is different, but she cautioned that many people could benefit from GLP-1 therapy, particularly when guided by a clinician who has evaluated body composition and overall health.
Health guidance from international bodies underscores the need for careful consideration. The World Health Organization conditionally recommends long-term use of GLP-1–related therapies, including liraglutide, semaglutide, and tirzepatide, for adults living with obesity (BMI 30 or above) as part of obesity care. It does not endorse these drugs as a general-use option for all individuals regardless of health status. The guidance reflects the balance between potential benefits and risks, and emphasizes medical supervision rather than self-directed use.
Some experts caution that the decision to pursue GLP-1 treatment should be grounded in a person’s health history and potential risks, rather than marketing or availability. Salas-Whalen’s approach to candidacy—rooted in body composition and individualized risk assessment—offers one framework for clinicians navigating an increasingly common tool in obesity management. The growing use of these medications has prompted renewed attention to how best to identify who may benefit most while minimizing safety concerns and unintended effects.
For patients weighing their options, the core message from Salas-Whalen and other experts is clear: a data-driven evaluation that looks beyond the scale is essential. Body composition testing can illuminate where a patient stands in terms of visceral fat, muscle mass, and fat percentage, and help determine whether GLP-1 therapy is likely to improve overall health outcomes. In a landscape where access is expanding, medically guided, individualized decisions remain the standard.
