I don't think that I believe in starvation mode in the way that it is used by so many people lately. However, I DO believe that eating too few calories can and ultimately will have a negative impact on the body. I noticed someone mention people with eating disorders, and having known several I can without a doubt say that eating so few calories DID effect their metabolism. If you've ever met an anorexic after treatment, they regain the weight VERY quickly.
Do I believe that eating 1000 calories for a month will cause a person to go into "starvation mode" and stop losing weight? Not fully, IMO it really depends on the person. For some it may cause a stall, for others it might be just fine.
That being said, I DO believe that eating too few calories for weight loss causes weight loss to be more of a "diet" than a lifestyle change. It's what most (I know I'm being over generalized here, but bare with me) people have always done to try and lose weight in the past. Quick fixes to see the number drop, however as some of us know by experience, that is just how we yo-yo'd our way to our highest weight.
IMHO, there is no reason to drop your calories so low that you're hungry and irritable and tired. It's OKAY to not lose the weight RIGHT NOW. We're trying to form long lasting habits so that when we do reach our goal we are able to maintain it. There are people who believe that once they get to goal they can go back to eating the way they did before, and it's just not true. Maintenance is just as hard as weight loss, especially for those of us who have struggled with food for a majority of our lives.
If a persons calories are so low that they can't maintain that lifestyle (and I've seen it over and over again on 3FC), they lose a bunch of weight really fast, start seeing the scale slow down and show normal daily fluctuations, fall of the wagon because they get discouraged that they're not losing at the same rate, and binge their way back up to higher than before. Or a family gathering comes up, they treat themselves, and it turns into a binge and again they end up wayyyyy off the wagon.
Slow weight loss sucks, and it gets frustrating at times, but it's so worth it. It's worth it to work on managing our demons with food. It works on developing healthy habits and views on food and exercise (i always saw exercise equipment as modern day torture devices
). We deserve to fuel our bodies and feel good lose weight and be healthy and happy.
Anyways, I think I went on a bit of a tangent but it's something I do feel very strongly about... just in case you couldn't tell.