A human eating only 1000 Kcal per day would only be able to support a body weight of about 60lbs if sedentary. Are you sure your estimates are accurate?
The website fitday.com is also designed to compute calorie and nutrient intakes from food, and might be a good way to double-check your spreadsheet calculations.
There's also software that can track your nutrients and calories. Toying with it, adding random foods helps one get a better intuitive assessment of foods nutrition. After a while you'll just start to know what to roughly expect of the food on your platter.
You are right. I did pay attention to the serving sizes that are on the labels, but since I don't really measure the amount of rice I eat in cups, I had to estimate. Getting a more accurate estimate is next on my list.
However, note that I wasn't starving (see my other comment reply to CasioTheSane).
I have definitely noticed changes in food cravings with changes in diet- around a year or two ago I switched to one that killed my desire to snack (by providing me enough sustenance in meals). It's great to be able to identify the "I'm craving fat" feeling, and know that your diet is such that you can whip up a batch of cookie dough and eat it straight and it'll be the right decision.
WolframAlpha is pretty good for calculating all this automatically - probably much faster than the spreadsheet. For example:
Recently I decided to try an intermittent fasting diet. To do so, I had to figure out how much I could eat on my off/down days. I realized I didn't have a very good idea about how much calories my meals have, and as I was thinking about it, I started to get curious about my diet overall. How many calories do I get a day? How much of it is from fat? Do I get enough vitamins? Etc, etc, etc. All very basic questions, and since my meals are very regular, there was an easy way to find out!
(Note: anytime you feel curious and are about to find something out, make some predictions. I didn't, but I really wish I did, because I was very surprised by my findings.)
It took only a couple of hours, and here is the result.
If you scroll down, you can see that my usual Breakfast+Lunch+Dinner only nets about 1000 calories and gives 30% daily value of fat. No wonder I crave cookies and chocolate so much!
There are many surprising results that I got from this. And knowing that I've been eating like this for the past few years... Wow. This is the epitome of a low hanging fruit. I can't believe I didn't do this analysis earlier!
Edit: I was not trying to say that I only get 1000 calories a day. Of course I get more than that, but the rest is from cookies and post-meal sweets. I always thought I just have a sweet tooth, but the fact that I wasn't getting enough calories from my main meals can also explain this.