Currently on a shame sort of weight loss path. - 500 calories a day, still gaining fitness and strength on the bike (MV SSB2 was +4 watts, -3KG). I feel fine on this and have plenty of energy but I don’t think I would like to go - 1000 just for some extra quick gains. No real experience but just based on how things are going now.
If you are going - 1000 for a couple of weeks, make sure you keep your protein intake high:
“One study compared the effect of low protein intake (1.0 grams per kilogram per day) to high protein intake (2.3 g/kg per day) on lean body mass over a short term caloric deficit. On average, the low protein group lost about 1.6 kilograms (3.5 pounds) of muscle mass while the high protein group only lost 0.3 kg (0.66 pounds) of muscle mass (6).”
Oh, one thing to add. Perhaps the most important question. How important is that 1,5/2KGs less for your race. Is it worth the risk that you might feel less good on the bike?