Caloric intake: While it is true that less calories usually means more weight loss, some diet plans are strict and can leave you feeling hungry most of the time. Additionally, some people need more calories because of metabolic issues or high activity levels, and low-calorie plans might be insufficient. Think about whether a diet plan will keep you full.
If you're trying to lose pounds, your IBW is your goal weight; for maintenance, your IBW is your current weight. For instance, if you weigh 135 pounds and you want to maintain that, you need about 1,890 (135 x 14) calories per day. This is a very rough calculation; for a more accurate assessment, have your metabolic rate tested by a fitness professional.
It's no surprise that Dr. Dean Ornish's program is such a powerful tool for weight loss, considering its easy adaptability as a lasting lifestyle. The diet is mostly plant-based, keeps sodium intake in moderation, and limits coffee to a cup a day (two cups decaf) — so if you're looking to lose weight while keeping your java flow, you may want to consider another plan.
The Academy of Nutrition and Dietetics (AKA the top nutrition authority in America) released a revised paper this year saying that both vegetarian and vegan diets are best for people's health as well as the environment. If you're not ready to make a complete shift to meatless and cheese-less, consider "part-time" vegan and vegetarian plans, where you eat mostly plant-based at breakfast and lunch or on weekdays, and then eat fish, meat, dairy, and eggs only during designated times.