4 lbs. a week is rapid fat loss. Depending on how you have calculated your LBM and protein requirements, you could be hungry.
Sue is the real expert at evaluating typical food ingredients. If she doesn't reply immediately, you might do a search on her posts, especially her "conversation" with Satu last fall.
"The Top 100 Zone Foods" contains great information if your interests lead that way.
Last weekend I was reading "The 120-year Diet", written about 15 years ago. It claimed that 1500 calories of organic food deliver the same nutrients as 3,000 calories of mass-produced processed food. An interesting angle, if there's any truth to that statement.
Pavel, I agree with Charlie that 15 lbs lost in 4 weeks is a bit too high. It probably indicateds you aren't really in the Zone. IMO this would account for the symptoms you are describing now. I'd normally offer to review your block requirements and a sample of your menu in an average day, but due to the fact that tomorrow is a holiday and the next day I'm having a very major surgery, I probably wouldn't have time to review it. If you can post your LBM, type of exercise and amount of time spent on it in one week, and a sample of a daily menu including specific foods and amounts of each food, maybe someone will take a look and offer suggestions.
Another suggestion would be to reread your Zone book. I've seen this suggested by dr. Sears. Sometimes you'll pick up on someting you didn't notice at first. ("A Week in the Zone" or "Mastering the Zone" is a good choice for this.) But be sure to use the Zone food block guide on this site. It's the most up to date.
If all else fails, look at the picture of a day of meals in the Zone(on this site). Then, using divide the plate method, try to make your meals look like those in the pictures.
And to Charlie, that is certainly interesting info about the nutrient values of OG foods. Wonder if it is true? I've been eating OG as much as I can for years, and since I had the early stage breast cancer 2 yr ago, I'm eating [b:8c6925400c]only[/b:8c6925400c] OG for all dairy, meat and poultry.