Diets don't work long term

Which Are Worse: Calories from Carbs or Fat? - TIME:

Scientists know that on a molecular level, different types of starch and different types of fat have varying effects when they hit the body. But in terms of weight loss, low-fat diets and low-carb diets overall are equally effective (and, most of the time, neither will help you keep the weight off long-term), says Walter Willett, chair of the department of nutrition at Harvard School of Public Health.

Emphasis mine.
There is, obviously, more to the article, and I encourage you to click through and read it. However, the part in bold really struck me. Did a mainstream magazine actually just admit that diets don't work in the long run? Somebody pinch me!