Working out at first may seem to completely drain a person of any energy. Some people may have to scale back their exercise sessions when they first start. It could feel as if they will never be able to move again, yet working out on a regular basis can provide a person with a new energy source. Their healthier body may stop resisting them and start feeling better after only a few weeks.
The issue with suddenly beginning an exercise program is that the body is used to the lack of exercise. It can be a comfortable feeling for some, and this is one reason for resistance. Those who are determined to get into better shape can often break past that first resistance, and their body often becomes used to the new activity level. When they are not exercising, their body may still be ready to move more. That is where they will find they have more energy for doing things they have long avoided as too much work.
The health benefits of getting fit are often touted as avoiding future medical issues, looking better, and feeling better mentally and physically. While all of these may be true, that added feeling of energy throughout more of the day can allow a person to do things they had given up for a lack of energy. It is just one more possible hidden benefit of working out and getting back into good physical shape.