Preserving Skeletal Muscle during Pharmaco-logical Weight Loss: A Practical Framework Integrating Nutrition and Eccentric Exercise

Objectives: Glucagon-like peptide-1 (GLP-1) receptor agonists and dual incretin therapies achieve clinically meaningful weight loss and improve glycemic control and cardiometabolic risk factors in routine care. Because the quality of weight loss matters, reduction in Dual-energy X-ray absorptiometry (DXA) -derived fat-free mass (FFM) during pharmacological weight loss raises concern that muscle-related compartments may also be affected and highlights an implementation gap in obesity care.

Methods: This clinical practice review used a structured narrative synthesis of literature identified through PubMed/MEDLINE, Cochrane CENTRAL, Google Scholar, Semantic Scholar, guidelines and consensus sources and reference-list screening. The search focused on pharmacotherapy-associated changes in body composition, dietary protein targets during energy restriction, and practical exercise strategies including eccentric training. Literature was considered according to direct relevance, clinical applicability, and consistency across available sources.

Key Results: A pragmatic co-therapy framework is proposed for initiation at the first prescription and scaled to symptoms, capacity, and comorbidity burden. Nutrition prioritizes daily protein targets, meal distribution, and a Mediterranean-leaning, minimally processed dietary foundation. Exercise may incorporate feasible eccentric-biased starter options, including controlled lowering tasks (e.g., squat-to-chair patterns) and low-burden locomotor options (e.g., stair descent or gentle downhill walking), embedded within volume-first, symptom-guided progression with clear soreness and pain guardrails. Implementation can be supported through multidisciplinary coordination and early follow-up to review tolerability, adjust plans, and address barriers.
Conclusions: The proposed framework provides a pragmatic template to operationalize muscle-preserving co-therapy from the start of obesity pharmacotherapy and to guide early titration based on tolerability and functional response.

Key Words: Glucagon-Like Peptide-1 Receptor Agonists, Fat-Free Mass, Body Composition, Protein Intake, Stair Descent Training

Glucagon-like peptide-1 (GLP-1) receptor agonists and dual incretin agents enable clinically meaningful weight loss in routine care, improving glycemic control and cardiometabolic risk profile (21, 28). Key mechanisms include appetite suppression, delayed gastric emptying, and central satiety signaling (7, 25). Yet, weight alone does not capture the quality of weight change.

Recent guidance, including the World Health Organization (WHO) guideline on GLP-1 therapies for adults living with obesity, emphasizes that pharmacotherapy should be embedded within integrated, person-centered care (behavioral support, nutrition, physical activity) (4). Within this broader framework, this report targets one implementation gap: addressing potential muscle-related decline during pharmacologically induced weight loss through a feasible co-therapy package (structured nutrition support plus scalable exercise options, including eccentric training).

DXA-based analyses suggest that GLP-1-based weight loss is predominantly fat-mass reduction, but the fat-free compartment also declines. A Lancet Diabetes & Endocrinology commentary reported that approximately 25-39% of total weight loss over 36-72 weeks was attributed to DXA-derived fat-free mass (24).

Because DXA fat-free mass includes water and organ tissue, it is a surrogate rather than a direct measure of skeletal muscle; nevertheless, a clinically relevant fraction may reflect muscle-related tissue loss (13, 20). Evidence supports adequate protein intake to help maintain muscle protein synthesis during energy restriction (27) and indicates that eccentric exercise can provide high mechanical tension at comparatively low metabolic cost and may support muscle-related outcomes and physical function (12). This is particularly relevant for sarcopenic obesity (excess adiposity with reduced muscle quantity or quality) (6).

Clinical Rationale for Muscle Preservation
Skeletal muscle supports insulin-mediated glucose disposal, resting energy expenditure, mobility, and independence. When pharmacotherapy is tapered or discontinued, weight regain is common if behavioral change is limited (29); after diet-induced weight loss, regained weight is mainly fat, potentially worsening the fat-to-lean profile even when body weight approaches baseline (2). Given associations between sarcopenic obesity and adverse outcomes, including increased mortality, mitigating muscle-related decline during treatment is clinically important (3). In routine care, appetite suppression can reduce protein intake, and exercise prescriptions may be perceived as inaccessible in deconditioned or symptomatic patients. To translate this clinical rationale into routine care, a muscle-preserving co-therapy package may be operationalized through structured nutrition support and feasible, scalable exercise options.

This clinical practice review was developed using a structured narrative synthesis of literature identified through PubMed/MEDLINE, Cochrane CENTRAL, Google Scholar, Semantic Scholar, guideline and consensus sources and manual screening of reference lists of relevant reviews and key articles. 

Searches covered January 2014 to December 2025 and addressed three domains: pharmacotherapy-associated body composition change, dietary protein targets during energy restriction, and practical exercise strategies with a focus on eccentric training. Because direct evidence for eccentric exercise during obesity pharmacotherapy is limited, the exercise component was informed mainly by randomized clinical trials and feasibility/safety literature from obesity and rehabilitation settings.

As this manuscript is literature-based and does not report new data collection or interventions, ethical approval and statistical analyses were not applicable. The literature identification and selection process is summarized in figure 2, and the full database-specific search strategies are provided in table 1.

Framework Components and Implementation
Component A: nutrition co-therapy (protein targets and practical skills): A pragmatic starting target during energy restriction may be ≥1.2g protein/kg/day, although both the appropriate denominator and clinical target should be individualized. In clinical practice, protein targets may be based on reference, target or adjusted body weight and further tailored according to age, baseline functional status, sarcopenia risk, comorbidity burden, renal function, appetite, and gastrointestinal tolerability (22). The rationale for adequate protein intake to support muscle-related health during weight loss is supported across obesity and older-adult contexts (5, 14, 17, 19). Operationally, protein targets should be embedded within a practical eating pattern rather than delivered as isolated numeric goals. Early pharmacological weight loss may provide a window for low-friction routine building, and brief dietary scripts such as low-appetite meal options, simplified shopping lists, or protein-focused meal structure may help translate targets into practice (21). A Mediterranean-leaning, minimally processed dietary pattern may serve as a practical default option for many patients, while requiring adjustments for appetite, tolerability, comorbidity, and habitual dietary patterns (1, 26). In this context, adequate fiber intake, unsaturated fats, and higher-quality carbohydrate sources may further support satiety, glycemic control, and overall diet quality (1, 18, 30). Delivery and documentation may be facilitated by a structured workflow with predefined assessment items, individualized targets, and follow-up templates to support consistency across providers and monitoring over time.

Component B: eccentric-biased exercise as a practical entry option: Eccentric loading can generate high mechanical tension at relatively low cardiopulmonary cost and perceived exertion, which may make it a practical option for selected low-fitness or symptomatic patients (16). Clinical syntheses indicate that, with familiarization and conservative progression, eccentric training can improve strength and function with low rates of serious adverse events; monitoring delayed-onset muscle soreness (DOMS) and symptom exacerbation remains central to safe implementation (8). For routine care, tiered options matched to capacity and access may be offered (e.g., controlled lowering in chair-based movements; controlled eccentric phases in presses or pulls; low-step stair descent with handrail support; gentle downhill walking). Where available and appropriately supervised, eccentric cycling or flywheel/isoinertial modalities may be considered.

Progression Guardrails and Integration into Broader Activity Guidance
A conservative, volume-first progression may be applied, increasing total work before external load or speed. Progression can be contingent on next-day pain and DOMS remaining low-grade and movement quality being stable over 48-72 hours; otherwise, progression may be held or the dose reduced (8, 16). A feasible starting option may be two nonconsecutive sessions per week, building duration or sets before intensity. As tolerance improves, concentric and aerobic components may be added consistent with consensus guidance and comorbidity profiles (9, 10, 23).

Operationalizing the Package in Routine Care
A pragmatic low-burden pathway may comprise brief baseline and follow-up functional checks (plus body composition assessment where feasible); a one-page nutrition starter plan (protein target, distribution guidance, low-appetite templates); a written starter exercise plan with, for example, eccentric exercise options and guardrails, and a 2-4-week review to assess tolerability and barriers. 
In older adults and patients with sarcopenia risk or low baseline fitness, lower starting volumes, closer early follow-up, and greater emphasis on tolerability and functional progression may be appropriate.
Early co-therapy may be considered particularly in patients with low baseline functional status, sarcopenia risk, rapid early weight loss, or low habitual protein intake. In routine care, indicators of low muscle reserve or functional vulnerability may include chair-rise difficulty, slow gait, low habitual activity, recent decline in strength or mobility, or clear deconditioning. Precautions should be individualized in osteoarthritis, frailty, diabetic neuropathy, and severe mobility limitations.

When medication is tapered, reinforcing food skills and movement routines may support weight stability and body composition outcomes (15). Optional remote delivery and digital support may reduce friction but should remain workable without specialized infrastructure. A schematic summary of the proposed framework is provided in figure 1.

Implications for Future Therapies
Muscle preservation may be considered a parallel implementation objective alongside weight loss within pharmacological obesity care. This package is intentionally pragmatic and complements, rather than replaces, comprehensive obesity management, including behavioral support, psychological well-being, sleep and comorbidity management, medication optimization, and referral pathways when indicated (21, 23). Looking ahead, as more potent incretin-based combinations and emerging triple-agonists advance through trials and enter practice (11), achievable weight loss is likely to increase, sharpening the clinical relevance of how weight is lost, not merely how much. For emerging triple-agonist therapies, implications for muscle-related outcomes remain partly extrapolative because direct body-composition evidence is currently limited. Embedding scalable muscle-preservation co-therapy, including explicit protein targets with distribution guidance and feasible exercise options, including eccentric training, implemented with conservative guardrails, may therefore represent a pragmatic adjunct in support of metabolic resilience and physical function, particularly in patients with low muscle reserve or functional vulnerability. Eccentric-emphasized exercise should, however, be regarded as one pragmatic option, while other established exercise approaches, including progressive resistance training, combined strength-endurance formats, and multimodal programs, may be equally appropriate depending on clinical profile, symptom burden, prior exercise experience, patient preferences, access, supervision, and likelihood of adherence.

This article presents a clinical practice framework based on a structured narrative synthesis rather than a systematic review. DXA-derived fat-free mass is a surrogate that includes non-muscle components and does not permit direct inference about clinically meaningful skeletal muscle preservation. In addition, although eccentric-emphasized exercise has been examined in obesity populations, including in randomized trials, the available evidence does not consistently reflect patients receiving anti-obesity pharmacotherapy. The proposed framework should therefore be interpreted as a pragmatic clinical model informed by the available literature rather than a definitive, validated co-therapy protocol.

Pragmatic trials should test combined pharmacotherapy plus explicit protein targets and structured exercise co-therapy using standardized outcomes, including lean mass, strength, function, symptoms, and adherence. Research should also compare delivery models (e.g., brief in-clinic initiation with early follow-up, with or without remote support) and different exercise modalities, including but not limited to eccentric-emphasized formats, to identify scalable approaches for routine care.

Conflict of Interest
The author has no conflict of interest.

Funding
No external funding was received for this work.

Ethical Approval and Informed Consent
Ethical approval and informed consent were not required for this clinical review.

Data Availability
This report is based exclusively on previously published literature; no new data were generated or analyzed.

Statement of Author Contributions
The author confirms being the sole contributor of this work and has approved it for publication. ChatGPT (OpenAI; GPT-5.2) was used to support English-language editing. The author wrote the manuscript, critically reviewed and edited all content, and takes full responsibility for the manuscript, including its content, statements, and conclusions.

What is already known about this topic?
- GLP-1 receptor agonists and dual incretin therapies produce clinically meaningful weight loss, yet DXA analyses commonly show concomitant reductions in fat-free mass, a surrogate that may include skeletal muscle.
- Skeletal muscle preservation is clinically relevant for metabolic resilience and physical function but is not consistently operationalized at pharmacotherapy initiation.

What does this clinical review add?
- This clinical practice review proposes a pragmatic co-therapy framework that can be initiated at the first prescription, integrating explicit protein targets and scalable exercise co-therapy, with pragmatic eccentric-biased exercise options.
- The framework specifies feasible entry strategies, conservative progression, and symptom-guided monitoring guardrails for routine care.

Practical implications
- Implementation can be supported through a low-burden starter plan, multidisciplinary coordination, and early follow-up to review tolerability and address barriers.
- Embedding muscle-preserving co-therapy alongside pharmacological weight loss may support functional outcomes, particularly in patients with low muscle reserve or functional vulnerability.