To understand the difference, we can put all the weight loss diet plans into several boxes:

a.) extreme fad diets vs. long term diet plans

Extreme fad diets focus on short term extreme weight loss (for example 5 Kilos in one week). Long term diet plans focus on a less extreme effect and can be healthier and longer lasting. Long term diet plans minimize the risk of the "yo-yo" effect (gaining all the weight back after a diet).

b.) carbs are good vs. carbs are bad

As discussed in the food facts section, carbs are "under hot discussion". Nearly all weight loss diet plans have their unique point of view. The diet plans range from nearly no-carb to relatively high-carb.

c.) cycle included vs. all-the-same

Some diet programs already recognize the importance of the cycle principle and include it. Such weight loss plans change e.g. the amount of calories allowed within a certain time period. Or they include an "eat-what-you-like" day once a week.

If a diet plan always calls for the same, it can be especially beneficial to take short breaks from it and experiment with a different plan for a week or so.