We often want to jump into a program and try and workout hours at the gym and suffer the soreness the next day. Exercise should be eased into our lives by continuing adding additional stress, effort and weight as the body adapts. It isn't designed for short bursts of enthusiasm marked by months long periods of inactivity.
Consistency is the main component in improving health. According to a study of obese participants consistent exercise (3X a week) for 12 weeks resulted in improved blood health, body mass, body fat, cholesterol, and oxygen volume (Dae-Young & Sun-Young, (2014).
It isn't so much the type of workout that is important. Walking, biking, treadmill, elliptic, swimming and most cardiovascular based sports get the job done. It is best to find an exercise that you can maintain and continue to do as your body allows you to. The biggest factor to success is engaging in fitness consistently throughout the week.
Dae-Young, K. & Sun-Young J. (2014). Effect of Aerobic Exercise on Risk Factors of Cardiovascular Disease and the Apolipoprotein B / Apolipoprotein A-1 Ratio in Obese Woman. Journal of Physical Therapy Science, 26 (11).