In my opinion, there are two groups of people who should take multivitamins:
Pregnant women (specifically prenatal vitamins)
People with a medical condition for which a doctor has recommended they take a multivitamin - such as malabsorptive diseases, including but not limited to Crohns, ulcerative colitis, pancreatitis, liver disease, and cystic fibrosis
Where the line is drawn (in my opinion) is when your primary care provider at your annual "well" exam suggests you take a multivitamin to "fill in the gaps" in your not-so-perfect diet. It is to the habitual multivitamin takers, who are otherwise healthy, that I am talking to.
The media is full of quick-fix advertisements designed to entice you to try their newest product. The weight loss industry is a multi-billion dollar industry, and it profits from you buying its pills and serums... and lies.
Would it be profitable for them to sell you a product that worked? Then you wouldn't be back to buy more.
They use media strategies and psychology to design their advertisements so you want to buy what they are selling in the hopes that finally, just finally, you will find the magic solution to the weight you've been trying to shed.
Why You Shouldn't Try Weight Loss Supplements
Just like herbal supplements, most weight loss supplements are not regulated by the FDA. FDA regulation is important because scientists there double check the work of the manufacturer's scientists to make sure the pill does what they say it will do, and that it is safe. Without this double check, manufacturers can fill supplements with various percentages of ingredients. Often companies will cite a scientific study where their pill lead to weight loss, but they leave out the fact that the pill they are selling you only contains a fraction of the active ingredient, so it won't be in sufficient quantities to work. So then you should just take more of the pills, right? Wrong. Because they aren't regulated by the FDA, companies can fill the pills with various ingredients, some of which can be harmful. For example, there have been numerous reports of liver damage caused by the popular supplement Hydroxycut. So many, in fact, that in April 2014 the FDA issued a Consumer Update report recommending that all consumers using Hydroxycut stop immediately. Hydroxycut led to liver damage so severe in one consumer they required a transplant. Another Hydroxycut user died.