Sarcopenic Obesity

Sarcopenic obesity is the coexistence of excess body fat with low muscle mass and function. It carries a greater risk of disability, falls, cardiometabolic disease and death than either condition alone.

Prevalence is roughly 5% to 10% of older adults and varies widely with the definition used. It rises with age and with higher body mass index.

Pathophysiology. Visceral fat releases inflammatory cytokines and promotes insulin resistance, which drives muscle catabolism. Fat infiltrates muscle (myosteatosis) and reduces its quality. Weakness and pain reduce activity, which favours further fat gain, creating a vicious cycle.

Body mass index may be normal or raised, so the diagnosis is easily missed. Look for weakness, slow gait, falls, breathlessness on exertion, and coexisting type 2 diabetes, hypertension, dyslipidaemia, osteoarthritis and fatty liver disease.

Show excess adiposity by waist circumference or body fat percentage, then show low function by grip strength and low muscle mass by dual energy X-ray absorptiometry or bioimpedance, with muscle expressed relative to body weight or body mass index. Screen for diabetes, lipids, liver disease, thyroid function and vitamin D deficiency.

Differential diagnosis.

• Obesity with weakness from deconditioning, pain or hypothyroidism.
• Cushing syndrome and steroid myopathy.
• Heart failure, COPD and chronic kidney disease with fluid retention.

Combine a modest energy deficit (about 500 kcal daily) with protein 1.0 to 1.2 g/kg daily, resistance training and aerobic exercise 3 times weekly. Avoid rapid weight loss, which removes muscle and bone. If medicines for obesity or diabetes that reduce lean mass are used, always add resistance exercise and protein and check muscle function regularly. Replace vitamin D if low.

Monitoring. Weight, waist, grip strength and body composition every 3 to 6 months, together with glucose, lipids and blood pressure.