Just because you've been able to carve out 90 minutes a day for cardio doesn't mean you should be doing that much -- at least at first. Unless you're already fit, going for 90 minutes at a time every day might be too much. It's important to start slowly and give yourself breaks to prevent burnout and injury. Your body and mind will thank you for the slower, easier transition.
If you're new to exercise, talk to your doctor to get her advice on a good starting workout for you and your situation. The first time you do your workout, keep a watch handy so you can time how long before you get really tired. While pushing yourself to work out longer or harder can help you lose more calories, you'll set yourself up for injury by pushing yourself beyond your limits. Whatever that initial time is -- be it after 20 minutes or 60 -- only add about 10 percent to that time every week, recommends the American Council on Exercise. So if you managed 45 minutes the first week, add 4.5 minutes the next week, and then another 4.5 minutes the following week, until you're up to your target time.
Quantity Vs. Quality
It's also important to consider why you have this goal of doing 90 minutes of cardio every day. When it comes to exercise, quality is more important than quantity; basically, intensity may be more important than doing long bouts of exercise. If you're spending 90 minutes on the treadmill and just going at a slow maintenance pace, you're going to burn some calories -- but if you're not depleted at the end of the workout, you may be wasting time that could be spent incorporating all-important strength training into your routine, or cooking yourself a delicious, low-fat meal.
Consider adding variety one or two days a week. Instead of that long, drawn-out routine, try walking for two minutes, and then sprinting for another two minutes, cycling between the two about eight to 10 times. That 20- to 40-minute workout is a form of high-intensity interval training, which has been shown to increase your metabolism for an entire day following the workout. And since strength training is so important for your health -- and for helping you build muscle that leads to more efficient weight loss -- also consider replacing one or two longer cardio workouts with a strength training session.
That's not to say the long-format workouts aren't beneficial, and for some people, they're a way to get away from it all. Walking through the woods for 90 minutes can be a serene addition to your day; cycling to work can be a way to save money and avoid stress-inducing traffic. If you're a beginner or intermediate exerciser, though, you'll probably have to stick to low to moderate-intensity exercise to maintain it for 90 minutes at a time. Instead of cycling fast, you may have to set a slower pace. Instead of jogging briskly, you may have to walk. Among the lower-intensity forms of exercise, a 155-pound person can expect to burn roughly 447 calories walking at 3.5 mph, 594 calories cycling at 12 mph, or 780 calories using a rowing machine at a moderate pace.
To maintain your 90-minute sessions day after day, you need to focus on proper fueling. Yes, you're aiming to lose weight, but your body still needs fuel to keep going. When you work out longer than 60 minutes at a time, your body's stores of glycogen -- basically stored carbohydrates -- will get depleted and you may experience a significant drop in energy. Replenish your stores by eating a bar or energy gel or a banana with almond butter. Focus on whole grain breads and pastas and legumes to keep your glycogen stores up. You'll also need plenty of protein to build muscle. While the amounts of each will vary for every person, your daily calories should consist of 50 to 60 percent carbohydrates, 12 to 20 percent from protein and about 30 percent from fats. Also, drink plenty of water: at least half your body weight in ounces is ideal, if not more due to your long bouts of exercise. Another way to keep up your energy is take at least one day off every week, to help your body rest.