-
It looks like you are keeping your general food intake at a dependable 1500-1600 calories.
So unless you are heavily reducing carbs, I would suggest specifically fuelling your workouts.With your caloric deficit, you could probably eat exactly the calories needed to replace your cycling calorie burn, and still make fast progress. I'd go for more satisfying food choices pre/during/post workout than energy gels though.
2 hours on the bike will be at least 1000 kcals, which is the equivalent of 10 medium bananas, or 2 very large bowls of porridge.
1500 intake at your current weight + bike riding, sounds like on some days you are approaching 0-500 kcals for the day?
A 2500 kcal deficit is basically starvation. Which clearly will work for weight loss, but unsurprising that you’re feeling lethargic!
Definitely recommend reviewing the calorie intake, otherwise you will rapidly overtrain and get permanently fatigued, or get sick or both.