Anabolic-Androgenic Steroids and Body Composition
Anabolic-androgenic steroids increase lean mass and lower the percentage of body fat but do not reduce fat mass, and they carry substantial cardiovascular, liver, hormonal and psychological harms.
Plain English
Patient-Friendly Explanation
Anabolic-androgenic steroids are synthetic versions of testosterone. They are legitimate medicines for a small number of conditions, such as testosterone deficiency caused by disease, but they are also used without a prescription to build muscle and change appearance. Their effect on body composition is real but is often misunderstood. In a study of 35 experienced male strength athletes, eight weeks of self-administered anabolic steroids increased body weight by 4.4 kilograms and lean body mass by 4.5 kilograms, while the percentage of body fat fell from 17.0 to 16.0 per cent; absolute fat mass did not change. In other words, the medicine adds muscle rather than removing fat, and the apparent improvement in fat percentage is arithmetic, caused by a larger lean compartment. That matters because a patient may gain weight on the scales while looking leaner. The harms are the reason these medicines are not used for weight management. They lower HDL cholesterol, in one controlled study by 25 to 27 per cent, raise blood pressure, and cause acne, breast enlargement in men, shrinking of the testicles, reduced sperm production and, on stopping, low mood with loss of the gains. Long-term high-dose use is associated with liver injury, thickened heart muscle, rhythm disturbances, raised clot risk, tendon rupture and mood and aggression changes, and some users develop persistent testosterone deficiency after stopping. In Singapore these medicines are prescription-only and are not licensed for athletic or cosmetic use, and they are not a treatment for obesity.
Medical
Clinical Definition
Anabolic-androgenic steroids (AAS) are synthetic testosterone derivatives that bind the androgen receptor and produce dose-dependent increases in skeletal muscle protein synthesis and lean mass. In a prospective study of 35 male strength athletes, eight weeks of self-administered AAS increased body weight by 4.4 kg and lean body mass by 4.5 kg and reduced the percentage of body fat from 17.0% to 16.0% without changing absolute fat mass; the changes were still partly present six weeks after withdrawal, and short and long courses produced comparable effects. A double-blind study of nandrolone decanoate given to bodybuilders produced a 25% to 27% fall in HDL cholesterol that reversed within about six weeks of cessation, together with a rise in diastolic blood pressure. Athletes studied after several years of use had increased lean leg mass, capillary density and myonuclear number but lower absolute and relative squat force per unit of lean mass, indicating that hypertrophy is not matched by proportionate strength. Documented adverse effects include dyslipidaemia, hypertension, hepatotoxicity, acne, gynaecomastia, testicular atrophy and suppression of spermatogenesis, mood disturbance, cardiomyopathy and arrhythmia, thromboembolism, tendon injury and, after cessation, secondary hypogonadism requiring endocrinological assessment. Stopping is associated with loss of lean mass, depressive symptoms and reduced motivation. AAS are prescription-only in Singapore and are not indicated for obesity or for body composition improvement in healthy people; supraphysiological use is a form of drug misuse and should be managed with non-judgemental counselling and monitoring of lipids, liver enzymes, blood pressure, haematocrit and gonadal function.
Key Insight
Why It Matters
Patients ask about steroids for weight loss, and the clinical answer is that they are not a weight-loss treatment: they increase muscle without reducing fat, and they cause real harm to the heart, liver, lipids and hormonal system. In a weight clinic the practical concerns are that anabolic steroid use can coexist with disordered eating and compulsive exercise, that it can mask or worsen liver and lipid results on routine monitoring, and that stopping can be followed by depression and low testosterone needing proper assessment. Any patient using them should be offered monitoring rather than judgement.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
