On the contrary, working out before bed will cause you to lose sleep precisely because of the heart rate problem. Your heart is pumping too fast to fall asleep or to enter the deep REM sleep necessary to repair the muscles you’ve exercised. Your body temperature is too high, retarding the release of certain vital sleep-related hormones. Because your heart is beating faster, the body is getting a lot of oxygen, which means you feel more energetic, not more tired. The tired feeling after working out is many, many hours after the work-out has passed. This is one of many reasons most people choose to work out in the morning.

The previous poster is correct; working out increases your heart rate for several hours afterwards, so it is best to do it in the morning. I believe by “all day” he meant “most of the day”, since working out within a couple of hours of bedtime will cause a restless sleep. Additionally, you won’t lose weight in your sleep that you wouldn’t have lost during the day; the weight lost in sleep is water weight caused by the brief fasting while unconscious.

People just need to realize it takes time to change your body, especially if you spend a year to get out of shape, you won’t be able to get back into shape in a month.