How Hormonal Decline Drives Sarcopenic Obesity — And What Doctors Can Do

Sarcopenic obesity (SO) is increasingly recognized as a distinct clinical syndrome — not merely the sum of obesity and sarcopenia — in which excess adiposity coexists with reduced skeletal muscle mass and function, compounding metabolic and functional risks beyond either condition alone. Its global pooled prevalence is approximately 14%, though estimates range from 3% to 55% depending on diagnostic criteria, and rates climb substantially in older adults, those with functional impairment (33%), cognitive impairment (35%), or multiple chronic diseases (19%).

This comprehensive narrative review from researchers at Sapienza University, Rome, focuses on the endocrine mechanisms that drive and perpetuate SO. The authors argue that hormonal alterations are not merely associated with SO but are mechanistically central to the adverse muscle-fat crosstalk that defines it. Age-related declines in anabolic hormones — testosterone, estrogens, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and thyroid hormones — impair protein synthesis, satellite cell activation, mitochondrial function, and fat distribution. Simultaneously, increased catabolic signaling through elevated glucocorticoids and RAAS overactivation promotes proteolysis, visceral fat accumulation, and systemic inflammation, while impaired sympathoadrenal signaling blunts lipolysis and thermogenesis in obese individuals.

A particularly valuable contribution of this review is framing specific endocrine diseases — hypogonadism, GH deficiency, hypothyroidism, Cushing syndrome, primary hyperaldosteronism, and type 2 diabetes/insulin resistance — as experimental and clinical models of SO. Each condition recapitulates cardinal features of SO through defined hormonal mechanisms, offering insight into shared molecular pathways. For example, hypercortisolism (as in Cushing syndrome) causes selective type II muscle fiber atrophy via 11β-HSD1 activation and simultaneously drives visceral adiposity, closely mirroring SO pathophysiology.

On the therapeutic side, testosterone replacement increases fat-free mass and strength in hypogonadal men but shows inconsistent functional benefits. Selective Androgen Receptor Modulators (SARMs) show emerging promise for lean mass gain with potentially fewer side effects. GH therapy reproducibly increases fat-free mass but lacks consistent functional evidence, particularly long-term. Levothyroxine can restore muscle function in overt hypothyroidism. RAAS inhibition via ACE inhibitors or ARBs yields mixed results for muscle outcomes. Beta-2 adrenergic agonists improve body composition in short-term studies but are not yet established as SO therapies. Myostatin inhibitors and ghrelin analogues remain investigational.

The authors highlight a critical diagnostic gap: existing obesity and sarcopenia definitions are insufficient for SO, and a relative muscle deficit in the context of elevated fat mass can impair metabolic health and physical function even without absolute sarcopenia. They endorse the SOGLI (ESPEN/EASO) 2022 consensus framework, which integrates adiposity assessment with muscle mass and function criteria. Overall, the review makes a strong case for studying endocrine pathways in an integrated fashion to identify precision hormonal targets that restore anabolic-catabolic balance in SO.