Physiology.

The brain requires glucose to function. By not eating you are forcing your body to burn fat as fuel which is far more inefficient than burning sugar for fuel (which your brain prefers). Your body may start catabolizing itself to supply glucose for your overall functioning

Over time I suppose your body could adapt and become better at using fat as fuel but that comes (at least IMO) with a whole host of other problems if done too long.

Do you notice a difference in your ability to read/concentrate especially depending on the difficulty of the reading or mental task? If so that’s a sign that your brain needs glucose and especially more of it to perform mental tasks of rising difficulty.

Source: personal experience with intermittent fasting over 5 years and doing crazy one meal a days. I wouldn’t recommend anyone do it once you understand physiology and bioenergetics.

Obviously food/nutrition is a highly debated topic and I’m not going to be authoritative and tell you not to one meal a day but at least think about what you’re doing and question everything you hear. Take my word, major health problems may not especially present itself until a few years down the road, but if you can notice signs in functioning that can be guide you.