Long-term fatigue and long-term nutrition can have effects that languish. Fueling properly one week won’t immediately compensate for having been in a calorie deficit for several weeks (intentionally or not).
Feeling fatigued for 4–5 days points to being unable to recover from your training. Personally, the biggest factor is
- a sufficient amount of sleep long-term — or rather, lack thereof.
- The next important thing is nutrition on and off the bike. Currently, I am in a calorie deficit, too, as I am trying to lose some more weight. But I can definitely tell, it has an impact on my recovery and my performance on threshold workouts specifically.
- And as a consequence, you might have to cut back your training. Too often I hear “you need to train more to get faster”, but they forget to add “if you can recover”. The last bit is not free. IMHO it is better to opt for less volume, if you are more consistent as a result.