Yes generally a person weighs the least first thing in the morning before eating and the most in the afternoon or evening. Sometimes kidney disease can cause swelling and fluid buildup so could gain weight more easily than normal. Or any disease states or health issues that increase fluid build up or swelling can cause weight gain. If exercising and sweating a lot need to drink approximately 16 oz for every pound lose from sweating excessively. Also consume foods or liquids with electrolytes if working out more than 20-30 minutes since want to avoid dehydration. I studied nutrition in the past and am into nutrition and exercise.