GLP-1 receptor agonists have transformed weight management, producing substantial reductions in body weight and improvements in metabolic health. But for the female athlete, an important question extends beyond how much weight is lost: What happens to the muscle, bone and other tissues that support athletic performance?
In Part 1, we explored how appetite suppression may affect energy availability when combined with training. This week, we’re examining the composition of weight loss and its potential implications for strength, skeletal health and performance.
While clinical trials provide valuable information about body composition during GLP-1 therapy, studies specifically examining performance outcomes in female athletes are lacking. Much of our understanding must therefore be extrapolated from populations with overweight, obesity or metabolic disease.
Weight loss is not just fat loss
Weight loss generally includes both fat mass and lean mass. Lean mass includes skeletal muscle, but also water, organs and other nonfat tissues. This distinction matters because a reduction in lean mass does not necessarily represent an equivalent loss of functional muscle tissue.
Studies of GLP-1 receptor agonists have reported that lean mass may account for approximately 25–38% of total weight lost, although estimates vary by medication, population and measurement method.
For individuals with obesity, substantial fat loss can provide meaningful metabolic and functional benefits, even when accompanied by some lean mass reduction. However, the implications may differ for a normal-weight, highly trained athlete.
Skeletal muscle is essential for generating force, producing power, maintaining metabolic function and supporting movement. For an athlete, the question is not simply how much lean mass is lost, but whether that loss compromises muscle function, strength or the ability to train.
What about bone?
Bone is another important consideration, particularly during perimenopause and menopause. It continuously responds to mechanical loading, nutritional status and hormonal signals. Weight-bearing exercise and resistance training stimulate skeletal adaptation, while adequate energy availability supports bone remodeling.
Research examining GLP-1-associated weight loss has produced mixed findings. Some studies report reductions in bone mineral density and increased bone resorption, particularly with substantial weight loss. However, these findings do not establish that GLP-1 medications directly damage bone. Changes may reflect weight loss, reduced mechanical loading, nutritional factors or medication effects.
Interestingly, a randomized trial in adults with obesity found that combining exercise with liraglutide helped preserve bone mineral density compared with liraglutide treatment alone.
For midlife female athletes, this is particularly relevant because the menopause transition is already associated with accelerated bone loss. However, whether these findings translate directly to athletic women using GLP-1 medications remains unknown.
What does this mean for athletic performance?
Muscle and bone are not simply components of body composition. They are essential to athletic function.
Weight reduction may improve certain aspects of performance, particularly in activities where moving less mass provides a mechanical advantage. Conversely, losing functional muscle or inadequate fueling could compromise strength, power, recovery and training adaptations.
Weight loss alone cannot tell us whether athletic performance is improving, declining or remaining unchanged.
We currently lack studies examining GLP-1-associated changes in VO₂max, strength, power or sport-specific performance in female athletes. Consequently, we cannot assume that changes in body composition necessarily translate into improvements—or impairments—in athletic performance.
Why this matters after 40
For active women over 40, preserving muscle and bone becomes increasingly important as the hormonal changes of midlife influence body composition, skeletal health and physical function.
Resistance training, appropriate skeletal loading and adequate nutrition remain central strategies for supporting these tissues. For women using GLP-1 medications, sufficient protein and total energy intake may be particularly important when appetite is reduced.
Although these strategies are supported by broader exercise and nutrition research, specific protocols for midlife female athletes using GLP-1 receptor agonists have not been established.
The Bottom Line
GLP-1 receptor agonists can provide substantial metabolic and weight-management benefits when appropriately indicated. But for the female athlete, the quality of weight loss matters as much as the quantity.
A lower number on the scale may be beneficial, but it does not necessarily indicate improved athletic function. Changes in body composition must be considered alongside strength, recovery, performance and overall metabolic health.
For the midlife female athlete, the more meaningful question may be:
Am I preserving the strength, skeletal health and physical capacity that will allow me to keep doing what I love?
In Part 3, we’ll explore how menopause, metabolic health and individual clinical circumstances influence decisions about GLP-1 therapy in athletic women over 40.
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