Unexplained Weight Gain

Weight gain that feels unexplained usually has an explanation that is simply not visible day to day. Small, sustained energy surpluses accumulate: an extra 100 kcal a day is roughly five kilograms over a year. Portion drift, liquid calories, and reduced non-exercise movement after a job change or injury are the commonest drivers. Medication is the most under-recognised cause. Several antipsychotics, some antidepressants, insulin and sulfonylureas, corticosteroids, beta-blockers, gabapentinoids and some hormonal contraceptives all cause measurable weight gain, and the effect can begin within weeks. Rapid gain over days is fluid, not fat — fat gain is metabolically limited to roughly a kilogram a week. Sudden swelling with breathlessness or ankle oedema points to heart, kidney or liver disease and needs assessment rather than dieting. Hypothyroidism does cause weight gain, but typically two to four kilograms of mostly fluid; a large gain blamed on the thyroid usually has another cause running alongside. Cushing's syndrome is rare and has distinctive features: central obesity with thin limbs, purple striae, easy bruising and proximal muscle weakness. Sleep restriction reliably increases hunger and preference for energy-dense food in controlled studies, making chronic short sleep one of the most modifiable contributors.

• •Steady increase in weight without diet change
• •Clothes tightening around the waist
• •Ankle or leg swelling
• •Facial puffiness
• •Fatigue
• •Cold intolerance
• •Increased appetite or cravings
• •Abdominal bloating

• •Sustained small energy surplus
• •Medication side effects
• •Chronic sleep restriction
• •Reduced physical activity or injury
• •Hypothyroidism
• •Polycystic ovary syndrome
• •Perimenopause
• •Fluid retention from heart, kidney or liver disease
• •Cushing's syndrome (rare)
• •Stress and cortisol-driven eating

Persistent weight gain reflects a sustained positive energy balance, but the reasons behind that balance are often hormonal, pharmacological or behavioural rather than a simple choice. Insulin resistance, leptin resistance, medication effects on appetite and metabolic rate, sleep-driven ghrelin elevation, and loss of incidental daily movement all shift the equation without any conscious change in eating.