I've been swimming a mile (64 lengths of a 25 meter pool) several times a week. I've swum laps regularly for about 25 years and I haven't noticed any difference with low carbing. I still have plenty of stamina. If anything, I have more stamina since losing some weight.

I've noticed a much bigger difference with land-based exercise. A year ago I could barely walk because of my weight -- my back and knees always hurt. Now, I can easily walk four or five miles at a pace of about 20 minutes a mile.

I think if you do a lot of aerobic exercise you can eat slightly more carbs and still lose. On the days I walk or swim (about five days a week), I eat about 10 grams more of carbs a day than on days I don't do any aerobic exercise.