Well, the thing is, there are always charlatans who sell on your hope and optimism, and food is a center of fad activity. Right now, there is an attempt to see chia seeds as some miracle diet additive that will do all sorts of miraculous things. They use this pathway because that's cult-leadership 101, in which they try to isolate you from contrary opinions--debby downer, hater, people who see "the old you", etc, etc, and drive questions to the assigned authority, which is typically themselves, or a reference that sez people like them...
Yo-yo dieting is not good for you. People do not, as a whole, have a capacity to lose weight quickly and keep it off. Most determined people gain back weight because life (typically job or health related) disrupts their habits, which involves attention to detail--like keeping a calorie/food journal. Losing weight fast is not actually good for you, never mind the likelihood of gaining it all back and more. Real live human bodies of normal, average, people who's mostly lead a sedentary life will react and conserve calories, make you tired feeling, and every delicious item out there is encouraging you to binge.
Using stimulants to lose weight isn't a great idea. First of all, you're dependent on them. Second, unless your appetite is suppressed, you'll feel hungrier and eat more. Third, most anything strong enough to really affect your body so as to lose lots of weight are going to have side-effects or damage your body.
We should drink puerh to enjoy it. If we happen to lose weight, it's entirely coincidental. Most people will not lose weight.