Are you experiencing any other symptoms associated with an abnormally slow metabolic rate? These may include fatigue, cold intolerance, water retention, among others. It wouldn’t hurt to have your doctor check your TSH (thyroid-stimulating hormone) levels next time you are in for a general physical. Hypothyroidism can often go undetected for an extended period of time and can result in weight gain despite a low daily calorie intake. It affects about 3 percent of the population and is treatable with one pill (levothyroxine) per day. It is unlikely that this is the cause, but if you’ve never had a full blood panel, it wouldn’t hurt to know your TSH for comparisons later in life.
This is a good point. If you feel like your weight gain really is freakish, talk to your doctor about it at your next appointment.
I didn’t read the responses, but I’ll throw my 2 cents in anyway. If you are working out, not eating enough is a bad idea. At least, not enough protein. If you are eating less while working out, that is going to slow down your metabolism instead of increase it. Feed your muscles what they need so they don’t break down. Having bigger muscles will require more calories to maintain them, so you will need to eat more, and just having muscle will take care of burning fat itself.