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Regular exercise helps boost energy levels and metabolism, and even helps the brain. You should incorporate 4-5 days of exercise into your regular routine to help keep you energized and strong. Make sure to exercise a few hours before bed so it doesn't interfere with your sleeping patterns.  A study at the University of Georgia found that exercise was more effective than some medication to help boost energy and keep you awake. Regular exercise also helps improve the quality of your sleep.  Try walking, cycling, swimming, or hiking. Do something each day for 30 minutes that gets your heart rate up. If you are sitting at your desk and feel like nodding off, try getting out of your chair and moving around. Take a walk around the office, do a few jumping jacks, run in place, or even do some squats and crunches. This helps get your blood pumping and wakes you up.  A study at California State University found that a 10 minute walk kept you alert for 2 hours afterwards, while a candy bar only kept you alert for 1 hour and led to a crash afterwards.  Stretch. Get out of your chair and touch your toes, stretch your back, and stretch your arms overhead.Stretching gets your blood flowing. When sleepiness hits, try doing some simple yoga poses. Yoga can help warm up the body and work as a natural stimulant.  Start with cat-cow pose. Get on your hands and knees with your shoulders and hips over wrists and knees. Move your spine rhythmically. With every inhale, arch the back and lift the sitting bones and chest. When you exhale, round the back and tuck your chin and pelvis. Start in downward facing dog. Lift your right leg up behind you. Round your spine while drawing the knee to your chest. Round your upper spine upwards as you keep the pelvis low. The right thigh should be against your chest and your knee should be against your nose. Return to downward facing dog. Repeat with the left leg. This raises oxygen levels in the blood and helps improve circulation. Breathe through your abdomen for the most effective deep breathing.  Sit up straight. Place a hand on your belly. Inhale through your nose. Make sure your belly pushes your hand out while your chest doesn't move. Push the air out through your lips. Complete this exercise 10 times. Inhale and exhale quickly through your nose. Keep your mouth closed and relaxed. The breaths should be short. Then breathe normally. Try for 15 seconds, adding 5 seconds until you can do this for a minute. A study presented at the SLEEP 2012 conference found that obesity and excess weight gain caused daytime sleepiness. Diet and exercise can help lose weight, in addition to helping improve your energy levels.

Summary:
Exercise. Move around. Do yoga. Breathe deeply. Lose weight.