I am just curious, can stress have an effect on weight gain? I am currently 20 years old. I have always been athletic and toned even though I work all day every day on a computer and eat junk food by the truckload. Recently it started to actually take its toll. I know I am at an age where metabolism begins to slow and my eating and exercise habits have become worse so than usual but I also started gaining upon high levels of stress. Is that possibly a factor?

Of coourse, stress is a factor. The whole effect of stress itself is that it alters body chemicals (such as pumps up adrenalin). Since our bodies function only according the the chemicals we release at given times, repeated stress episodes can have a profound effect in how your body is able to utilize the foods you put in.
Then again, that is assuming you actually put FOOD in your body. From the sounds of it, you haven't given much nourishment through the years for your body to even be able to handle what stress you give.
If weight gain is your only problem at this point, consider yourself lucky. The lifestyle you outlined WILL lead to more problems further on down the road, and weight gain may be the least of them.
Hate to be such a downer, but think about it. If you owned a Lexxus, caddy, jag, whatever fancy car, would you fill the tank only with the lowest grade fuel and have it serviced at K-Mart? I doubt it, cause it would eventually croak the car!
Well, my friend, you are LIVING inside the equivalent of a fancy car, and you've been pumping it full of the crappiest fuel you could find. If it isn't running so well now, you shouldn't be too surprised.
The good news is, you can fix it just by eating REAL FOOD! Not trying to be self righteous here. I'm even eating leftover pizza as I type. But, the rest of my food day will be filled with FRESH fruits & vegies and whole grains. I doubt I'll have much more in the way of breads or fat, except maybe some olive or hemp oil on some salad.
It really isn't difficult, expensive, time consumming, or any other negative to eat well. It is just a matter of choices.
Good luck,

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Copper
Let Miracles Replace all Grievances