I am down about 65 pounds from the highest weight. The first 30 came off about 16 years ago when I simply stopped eating such big portions. And about 7 years ago I began to exercise regularly, which helped some. But exercise alone will never do it.
After trying South Beach and failing at that after losing 11 pounds and then getting stuck, then gaining it back, I started just watching carbs and limiting portions even more, and that helped get another 20 pounds permanently off. Then I got onto a plateau which lasted 3 years or so. During this time I'd also given up red meat--pork and beef, to eliminate some of the saturated fat in my diet. But I was still eating too many calories and too much fat to get anywhere.
Last spring, fed up (pardon the pun) and looking for answers, I started reading about a plant-based diet, and didn't shut my mind to it, because I'd spent time with my vegan daughter and saw how tasty some of her cooking could be. I read books by Neal Barnard, Dean Ornish, John Robbins, Joel Fuhrman--you know, the type of eating that Bill Clinton has adopted. I haven't done it perfectly (and you don't really need to--95% is good enough) and have lost another 13 pounds since last April.
What you do is focus on plants and whole grains: salads, cooked vegetables, beans, brown rice, whole grain breads, fruit, nuts and seeds, while avoiding animal products: meat, poultry, fish and dairy. You stop eating these for three weeks or so and you stop craving them, or even wanting them anymore. You are constantly eating very nutritious food and you feel younger and more energetic. You get the fat out of your diet so you automatically consume fewer calories but still get full at each meal.
The best thing about this way of eating is that you never need to be hungry. You can always eat something and that something really fills you up. You find yourself liking those foods more and more, and greasy heavy stuff is no longer appealing. I know I won't be going back!
A plant based diet protects the heart, and is anti-cancer and helps improve a lot of chronic health conditions. And it's really fun--there is no "falling off" because you become happy and content with what you are eating. Yes I eat chocolate sometimes, and desserts, and when eating out stray into eating things like onion rings--but most of the time I'm eating healthy and feel really good. I still want to lose 20 pounds but I think I'll get there.
You can substitute a lot of things for your favorite meat and dairy foods: like veggie burgers, tofu sour cream, non-dairy milks, non-dairy butters. But mostly, especially if you like to cook, you can find a million recipes for making wonderful dishes made simply from cooked and raw vegetables, potatoes, rice, pasta, and fruit. These foods, contrary to that the big meat and dairy lobbies have taught us, have plenty of protein and calcium in them.
Did you know that the chimpanze, our closest relative, eats a diet in the wild that is about half fruit, and the rest mostly vegetables with a small amount of nuts and seeds? So why are we eating so much milk, meat, sugar and fat? The answer is that we have gotten away from our roots and have been trained to eat those things. We still need to cook our food, because we no longer have chimp teeth, but still the concept holds.
Books I recommend:
http://www.amazon.com/Complete-Idiots-Guide-Plant-Based-Nutrition/dp/1615641017/ref=sr_1_1?s=books&ie=UTF8&qid=1321508139&sr=1-1 http://www.amazon.com/Eat-Live-Amazing-Nutrient-Rich-Sustained/dp/031612091X/ref=sr_1_1?s=books&ie=UTF8&qid=1321508180&sr=1-1 http://www.amazon.com/Happy-Herbivore-Cookbook-Delicious-Fat-Free/dp/1935618121/ref=sr_1_1?s=books&ie=UTF8&qid=1321509148&sr=1-1Movies: "Fat Sick and Nearly Dead" and "Forks Over Knives" (Netflix streaming)
edited to add: If you have a huge amount of weight to lose, you will surely lose more than 13 pounds in six months. It will probably be more like 30-50 lbs depending on how much you have to lose. In "Eat to Live" there are personal stories that say it can happen.