the weigh gain could be due to a number of things, such as fluid retention, or maybe you ate somethin or need to go to the bathroom. our weight fluctuates every day by up to 2 pounds either way as our bodies gain water and food and use it and lose it etc. SO, what the best thing to do is weigh yourself once a week at the same time, eg i do it every monday morning. also, a better way to keep track of your fat loss is to measure your chest and waist etc. hope this helps!