I think people lose weight off of it because it's something healthy and you are feeding your body what it really needs, real and healthy antioxidants, phytonutrients, and vitamins. Just like Acai you lose weight with it because for some it's like the first time they've every had some decent antioxidants or even fruit for that matter in their diet
What I've learned from working at Super Supplements over the years is that the diet and weight-loss industry depends and abuses the ill-educated about weight loss. They know that many people don't know how to eat right or how to lose weight so they sell you something that gives your body what it should have been getting in the first place and call it a "miracle diet pill" but really you are just giving your body what it needed in the first place.
Example: "CliniCAL" ingredients: Chromium, Lactobacillus acidophilus, Capryllic acid, Glutamine, Glucommanan, Hoodia, Papaya, Uva ursi, Green tea, Apple cider vinegar, Grapefruit, Magnesium, Zinc, Copper, Tribulus terrestris, Fenugreek, Longjack, Kudzu root, DIM, Red clover extract, Oats, Pygeum extract, Stinging nettle leaf, Saw palmento berry, Black pepper extract
Chromium: balances blood sugar but if you just eat less sugar there would be no need to balance it in the first place
Acidophilus: helps with digestion, but if you eat right with lots of fiber you won't have a problem digesting
Glutamine: helps with sugar cravings, but when you eat less/no sugar, after a couple of months you will naturally get rid of your sugar addiction
Hoodia: reduces appetite. But when you eat healthy and a lot of fruits and vegetables you brain and body processes and reads them as real whole foods, you are getting a lot of fiber, protein, water, vitamins, etc which will naturally fill you up just as nature intended
Apple cider vinegar: helps with digestion also
Fenugreek: helps your body process hormones, but if you just eat right your body won't over-produce hormones so you won't have the need to have a processing aid herb
You see what I mean by this? African Mango makes you lose weight because you are eating something healthy, which is what we all should have been doing in the first place.