Remember these only enhance your existing training and diet. Pills don't burn fat or cut . Supps along with diet and training effect your metabolism . Look more closely at what you eat and then consider these insurance
Every thing has potential to cause problems if you get carried away , it depends in each individual person . Overall they are harmless to healthy individuals who use with moderation and care. Media hypes and overblown much as do paranoid careless people that really don't have experience to understand the details
In my experience: Most OTC "fat burners" on the market are some combination of caffeine, B-vitamins, and "herbal blend" (most of which are known to have a diuretic effect.) Most of what you are losing when you take them ends up being "water weight." This has pros and cons. The pros: it can offer temporary muscle definition (due to fluid loss),give you some energy, and appetite suppression (from the stimulants). These are temporary effects that will cease when the supplement is no longer taken. The cons: excessive fluid loss can to dehydration leaving you open to a host of other metabolic problems as well as negatively affecting your training volume. These types of supplements should only be used short term on cycles. There is no magic pill or shortcut. Only hard work, a clean diet, and dedication is going to get you lasting results.