According to the American College of Sports Medicine (ACSM), you should exercise for 150–250 minutes per week to lose weight. The organization also suggests that more exercise provides better results.2
If you want to keep the weight off for good, the ACSM prescribes a minimum of 250 minutes of moderate to high-intensity exercise per week.
To meet the ACSM guideline, you could simply exercise for 40 minutes every day. But that workout schedule could get boring, which may cause you to quit your program. In addition, to lose weight effectively you need to exercise at different intensity levels. This requires that you adjust your workout duration to accommodate the various workloads. It’s also helpful to keep track of your daily calorie needs for weight loss. This calculator can provide you with an estimate.