Let me preface my comments by saying I think most weight loss "diets" that are supposed to be a quick fix are a joke. When I use the word diet below I am instead talking about basic eating philosophies. I am not trying to bash any of the following eating ideologies. The average American eats a highly processed, high calorie diet and eats too much, so when I see people trying to improve their nutrition by following any program, my hat is off to them. Please don't take offense with any of my insights or opinions.
High-carb diet- I think starchy carbs like potatoes and white rice can be a problem for people trying to lose weight. If someone is a marathon runner, endurance athlete, or very active, they can certainly handle eating more starchy carbs than a sedentary person who sits in front of a computer 8 hours a day. I've recently realized that I have overeaten bread, cereal, and pasta for most of my life.
Vegetarian/Vegan- I think vegetarians are less likely to develop cancer, diabetes, and heart disease than the general public. I am not a vegetarian but have warmed up this philosophy over the last several years. It is not very common to see an overweight vegetarian.
Paleo-I like the natural aspect of this diet, but I think it can get a little extreme when it comes to avoiding any kind of grains. My other concern is that meat and protein is emphasized so heavily. I appreciate the fact that they try to eat natural, unprocessed food to fuel their bodies.
Raw Foods-I've seen cases of raw diets reversing the effects and severity of many diseases. Raw enthusiasts claim cooking your food kills the enzymes. A raw diet provides plenty of fiber, but the down side is it can be a real challenge to eat raw plants for every meal; however, I think most Americans would benefit quite a bit by moving in this direction by possibly having one raw meal a day.
My opinion- The world of nutrition can be confusing and even the experts don't always agree with each other. I think as a general rule, most people would be healthier if they ate more plant-based foods, especially more raw fruits and vegetables. I'm not against meat or animal products, but I think most people eat too much of them. Eating more nuts, seeds, healthy fats, and unprocessed foods is also a good idea.
I'm not a disciple of any particular diet. I try to take the good from each of these eating philosophies. The key is to develop long term healthy eating habits that are customized to you so they will be sustainable. You need to adapt your diet according to your lifestyle, needs, goals, and preferences. Remember the importance of moderation, balance, and variety so you don't get too extreme when it comes to your nutrition.