Lontong is lighter than rice, and most people do not know this. Because it is compressed and cooked with a lot of water, lontong is about 105 calories per 100g against 130 for cooked rice. A bowl with 200g of lontong is about 210 calories of rice, where a plate of nasi is 260 to 325.
The gravy is where the coconut milk lives. Sayur labu siam in santan is around 120 calories for a 150ml ladle, and it looks like soup so nobody counts it. The Padang version with gulai nangka and extra chili oil on top is thicker and closer to 180 per ladle.
The default breakfast at a Betawi stall is Rp 10,000 to 15,000 and includes one egg and one kerupuk, which is 450 calories with 15g protein. That is honestly one of the cheaper and lighter breakfasts on the street, as long as you do not add the semur tahu, the tempe orek and the second kerupuk.
The real trap is the lontong cap go meh and the lontong sayur with ayam opor and sambal goreng ati. Those are festival versions at 750 calories or more, and eating them like a daily breakfast is how people gain during Lebaran week.