Imagine a typical scene at the gym: people lifting weights, the aerobic room packed with dancers, people on treadmills staring at TVs … and someone lying on a mat waiting for lightheadedness to subside. There are several reasons for becoming lightheaded during a workout, including: hypoglycemia (low blood sugar), orthostatic hypotension (a drop in blood pressure when you get up or move), and dehydration.
Hypoglycemia is the result when blood sugar levels get too low. This can occur when sugar stores (glycogen) are used up too quickly; when blood sugar is released too slowly; or if an excess of insulin causes you to use up sugar too fast. Symptoms of hypoglycemia include fatigue, confusion, headaches, dizziness, feeling lightheaded when getting up quickly, heart palpitations, blurred vision and, when more serious, possible seizures.
If you want to burn body fat, and think that exercising without eating is the way to go, you may want to give that a second thought. According to the International Journal of Sport Nutrition and Exercise Metabolism, fasting before a workout does not improve fat burning. It also reported that eating before a workout increased VO2 max. In addition, those who ate before a workout burned fat more efficiently.
I suggest that you eat 60 minutes before your workout. Consume a small meal consisting of lean protein, a small amount of healthful fat, and some complex carbs. If you are pressed for time, a small shake made with high-quality protein powder, a shot of flaxseed oil or coconut oil, and half a banana may do the trick. This combination seems to be the best way to prevent hypoglycemia, keep you energized during the workout, and prevent an embarrassing nose-dive into the mat. Oh, don’t forget to drink water during your workout to prevent dehydration, which can also cause you to feel like you’ve hit the wall.
International Journal of Sport Nutrition and Exercise Metabolism, 21, 2011, 48-54