Fluid retention can be caused by normal hormonal fluctuations (in both men and women), muscle strain, sunburn, sitting or standing for long periods of time, a lack of sleep, medication such as hormones and steroids, and sometimes, though rarely, by heart or kidney problems. It is usually temporary and not a sign of a more dangerous problem. Drinking lots of water can actually help. If your symptoms don’t improve, you may want to consult with your doctor.