just another gosling
Join Date: Feb 2007
Location: Everett, WA
Bikes: CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
I don't race but I regularly do long fast rides and lose weight while still at top performance. No, don't diet the day before. Eat normally, but focus on ~60% calories from carbs that day. If it's a big ride and I've been training normally during the week, I'll do this for two days before the ride.
Assuming you're trying to lose weight:
If races are only on weekends, don't do the usual high carb recovery drink and recovery meal. Get plenty of after-ride protein instead. Then eat small portions of your normal diet, but including plenty of vegetables and protein until you need to up the carbs again for another race/ride. You'll have to experiment with your diet a bit to get this dialed in. If you feel weak during the race, you need to eat more, especially carbs, in the day or two before the race. If you aren't losing weight, you need to eat less, especially carbs, in the days when you aren't loading for a race.
If you also do a midweek race, that makes it more complicated. I'd be inclined to ignore fueling for that race other than having a good meal before, a sports drink during, and/or a bar just before.
A schedule like this will make it hard to do a lot of hard weekly miles. If that's your focus, you can ignore the above advice because you'll lose weight easily anyway, just by cutting back on your food intake a little. For the high-mileage case, I find it best to eat plenty on the bike, have a recovery drink after, and otherwise rely on meal portion size to drop the weight. Many people get good results from going out fasted early in the morning, or for an early morning trainer ride. Then do the hard workout later in the day when well fed.