AngS, FYI I have often found that when I up my exercise (to the point where my muscles really hurt the next day) the scales show and increase due to the swelling in my muscles. And bingo, happened to me today.
I am doing the eliptical trainer twice a week (walking and Tai Chi on other days) and I raised the resistance setting yesterday a notch. Scales show 1.5 lb increase this morning which I know is just the muscle soreness as have been squeeky clean on my carbs and calorie counts this week. And I do expect that over time I should see some increase from real muscle being added. I wish I had a clue as to how much weight is actually ends up being muscle, but a study found that older adults put on bed rest for just 10 days lost 1 lb of muscle in their legs alone. Also, after age 40, people typically lose 8 percent or more of their muscle mass each decade unless they engage in stengthening exercieses (weight bearing, or resistance). So if you have not actively excercised in a while and now start, you are likely to put back on some of the muscle lost. It should result in faster weight loss down the road….but sure is discouraging when you see it hit the scales and mask your weight loss in the short run.