I am a 34-year-old male who works out every weekend at the gym (aka "weekend warrior"). However, I came down with a cold, and am unable to go about my normal routine. I was wondering, considering my age and frequency of exercise, will I lose significant muscle mass or gain weight from missing one weekend?
One weekend is not going to do that unless you pigged out all weekend...
If you train heavy all of the time, train for strength so that you develop dense thick muscles, they don't disappear like the pump muscles of bodybuilders...