So I just started a diet. I went from eating about 1800 cals per day to about 1100 per day. I don't think I significantly increased my exercise. It has been 5 days. 5 nights where I went to bed hungry so, I knew it was working.

Yet, my scale has me gaining 2 lbs. This happens all the time.

This is how I get derailed.

Without knowing your height or weight, not sure how this applies to you. But my doctor has cautioned me never to go under 1300 calories and that I will lose more on that than anything lower because of how it will mess up my metabolism. That has worked well for me.

Personally I also think it depends on what we eat. Since I started eating mostly organic, non-GMO foods -- very little processed food -- mostly fruits, veggies and protein -- I have been able to maintain my weight loss and am losing again since I started being more diligent recently.

I have learned more about nutrition from Michael Pollan than anyone else -- he has several books out but also a lot of free videos on YouTube.

You don't need to be super hungry! I'd suggest calculating a modest deficit and using a tool (myfitnesspal, sparkpeople, chronometer, etc) that will assist you in tracking. Also, be patient! Weight loss is not linear. You may have weeks where it's masked by water retention from exercise, sodium, or even hot weather. If you have a consistent 3 weeks and don't lose anything, it would probably be time to tweak your deficit by subtracting more calories, adding more exercise, or both.