While stress levels do indeed affect one’s fat stores, there are of course a myriad of other factors involved in whether one stores fat or does not. These include but are not limited to:
Sleep quality and quantity
If you consider all these factors (and of course a number of others) then there are prolly a number of reasons that you may not have gained fat back then although you say you were more stressed.
Right here lets also acknowledge that something like “stress” is not easily gauged. We say things like, I was under more stress then, etc but there is no monitor, no ruler. Essentially you do not know how much stress you are under. We don’t even have a definition of stress. What you perceive as stress may not affect any cortisol response whatsoever. What you would never consider “stress” may indeed provoke cortisol-release.
Following that, when most of us talk about “losing weight” we do not really know what our bodies are losing. Water, fat stores, muscle mass, bone mass? You do not know. Some of us may, but the layperson just sees a number on the scale and if it goes south they smile, north they frown. This is intimately tied with society’s drive for women to just be lighter all the time. No mention of BODY COMPOSITION. Only numbers. This is terrible.
The people you mention that lost weight during stressful times were definitely going through what I describe above: they are canabolizing lean muscle mass and bone mass while storing fat. This inevitably leads to “skinny fat.” Same thing happened to me about 2.25 years ago.
Digression (stop reading if you’re bored;):
I’d like to take this opportunity to lambast the fear-of-cortisol in the paleo community. Well, in the xfit community, too. Acute cortisol-release from exercise is not something to be feared. Just know that it happens and maybe most of the time don’t overdo your exercise bout. However, people extrapolate from this that they should NEVER lift weights for more than an hour, etc. All the studies done on drug-free weight training individuals show that exercise bouts with the greatest cortisol release also lead to the greatest level of hypertrophy. Acute, temporary cortisol-spikes are not a big deal. Chronically raised cortisol, from things like the above stressful situations, running marathons regularly, not sleeping enough, etc, is bad and should be avoided.