I think courtney explained it quite well, but I'll answer your specific questions, as asked.
1) Starvation mode is really not a valid term - the word myth fits nicely. It's calories are restricted so much that the body shuts down metabolism in order to preserve fat stores that are already there. Reducing metabolism is a protection against starvation. If you continue to restrict calories, you will eventually lose weight, but as I said before, it won't be healthy.
2) Because "starvation mode" is really not a valid term - no, you aren't putting your body into starvation mode, but your body is protecting itself from the restricted calories.
3) What type of doctor assisted diet did you go on?
As both courtney and I have said, it's necessary to vary your caloric intake, as well as your exercise.
I think Barb explained this well. Her suggestion to vary your caloric intake by a few hundred cals is sound advice. That said, I'll explain in my own words and between the responses, perhaps you'll get a better understanding of what it is. Starvation mode is an explanation, theory for why weight loss may slow down when calories are significantly reduced. Reducing 500 calories a day would lead to a one pound weight loss in a given week. A 1000calorie reduction would lead to 2 pounds. However, if one reduces by even more, the body simply adjusts itself to the available calories, making the calories last. Therefore, instead of losing one pound per 3500 calorie reduction, you may lose less than one pound. Once the caloric intake is bumped up, the metabolism speeds up. To rev your metabolism back up, consider increasing your daily caloric intake, not a lot, just enough so your metabolism has plenty to work with.
On a side note, offering my opinion here, the typical dieter doesn't go into starvation mode. One has to really restrict to shock the body. I would say in your case, losing 100 pounds would be enough for your body to resist losing more for a period of time. You can read about starvation mode, just do a search. Perhaps search starvation mode myth to read more.
Hope this is helpful. Good luck on the last 20 pounds. Congrats on the accomplishment so far.
Sorry I didn't make my question clearer. 1.explain"starvation mode"
2.the fact I am burning more calories by exercise and my intake is less than 800cal.intake. is that placing body in "starvation. Mode"?
3.I lost wt with physician weight loss diet. Tks
BTW - congratulations on the 100 pound loss. Would you care to tell us how you did it?
"Please explain and could that explain why I have not lost any wt for almost a month." What is it you want explained?
There are different things that can cause a plateau....... it could be because you aren't changing your calorie intake or exercise, so your body has come to "expect" certain things, every day.......
For best results, vary your calorie count by 100-200 up/down on a regular basis. Additionally, if you perform the same exercises, your body just assumes that's what you're going to do every day and it's no longer a challenge. Change the exercises you do -- for instance if you walk, either go faster or slower, increase the time, swing your arms more, etc. Just like your mind needs a variety of things to think about, so does your body need a variety of foods and exercise.
If you are really using 800 calories more/day than you are taking in, your body could be trying to protect itself, by slowing down metabolism. If you continue, you will, eventually, begin to lose again, but it's not healthy.