There may be other mitigating factors, but the fact remains the vast majority of people can lose weight by changing lifestyle. If you look at an extreme case like Biggest Loser on US TV, these are very obese people who often give up and die or use shortcuts like fad diets or stomach stapling. I think even out of this group only 5% would ever have to resort to something that extreme. The show demonstrates that extreme problems can be met with normal weight lose measures, ie: the formula Galaxy uses to create a calorie deficit (albeit extreme exercise) . I like using the BMR weight loss formula, and its almost impossible not to lose weight that way. One extreme client I had lost 15 pounds in a week and a half using this method. He was a person who never had any limits to his eating whims and rose to almost 380 lbs. He lost 70lbs before some personal problems took him away from his weight loss goal. No fads needed.