Thanks for sharing. Anyway, here is my hypothesis which is the result of fairly intense thought and internet research over the past couple years.

Although we talk about peoples' metabolic rate as if it is a specific number, e.g. 1866 Kcal/day, the reality is that there is a range. If you eat towards the top of the range, you might gain a very small amount of weight but for the most part your body will adjust by running hotter. On the other hand, if you eat towards the bottom of the range, you will lose little or no weight but your body will adjust by running cooler. People sometimes refer to the cooler situation as "starvation mode," but I think this is an overstatement. "Starvation mode," i.e. eating at the bottom of your metabolic range is completely normal and probably healthier that eating at the top. Common sense says that revving your system hour after hour, day after day, puts more wear and tear on it.

Looking at your typical American in his late 20s or 30s who is slowly drifting up in terms of weight, one can infer that he must be eating at the top of his metabolic range -- otherwise he would not be gaining weight. The upshot is that he actually has a very fast metabolism at that time. Which goes against the conventional wisdom but when you think about it, it makes sense.

If such a person suddenly starts fasting, his metabolism will eventually adjust but the adjustment probably takes a few hours or days. In the meantime, this person will quickly burn through most of the readily available energy in his system and he will feel terrible pretty fast.

The other thing which is going on for a lot of people is mild addiction to certain foods. i.e. there are certain foods which produce a rush of good feeling (a bit like smoking a cigarette but less intense) followed later by withdrawal symptoms. Probably this is also part of the reason why it feels pretty terrible for some people to miss a meal or two.

Of course I don't know EY's individual situation that well, but I do think that it's completely normal for a lot of people to feel knocked out if they miss a couple meals. If you eat at the top of your metabolic range for years, the feeling of running hot seems normal and "starvation mode" seems pretty scary. But in my opinion, what's normal (in the sense of doing what your body is designed to do) is running cool. Starvation mode = normal mode.

Since your weight has been steady and/or drifting downwards, probably you are eating more towards the bottom of your metabolic range. Thus it's much easier for you to miss a meal than it otherwise would be.

Anyway, that's my hypothesis. I fully admit that I'm not an expert when it comes to diet, weight loss, etc. What I am saying is based purely on my own reasoning, research, and self-experimentation.