the weight gain could be a combination of muscle, water retention and depending on your diet some fat. but if I had to bet on it I'd say mostly water, fat and some muscle. the key to gain muscle and lose fat at the same time is a very strict diet. for example you need to add more protein and less carbs, and add good fatty acids like avocado, nuts, etc... 50/40/10 is the number that really worked for me, but we are all different, so keep trying until you figure out what works for you. make sure to stick to one diet for at least 4 weeks before making any changes or adjustments. and use the mirror to gauge your progress not the scale. good luck.
