We've all seen the ads on TV and in magazines that promise rapid weight loss and immediate results, but most of these claims are false. It's definitely hard to decipher the good from the bad but here are a few trigger statements [1] that should raise a warning flag for the product you're about to spend money on:

• "Lose weight without diet or exercise!"
  Achieving a healthy weight takes work. Take a pass on any product that promises miraculous results without the effort. Buy one and the only thing you’ll lose is money.
• “Lose weight no matter how much you eat of your favorite foods!”
  Beware of any product that claims that you can eat all you want of high-calorie foods and still lose weight. Losing weight requires sensible food choices. Filling up on healthy vegetables and fruits can make it easier to say no to fattening sweets and snacks.
• “Lose weight permanently! Never diet again!”
  Even if you’re successful in taking the weight off, permanent weight loss requires permanent lifestyle changes. Don’t trust any product that promises once-and-for-all results without ongoing maintenance.

What about miracle creams? Probably false too, so

• “Block the absorption of fat, carbs, or calories!”
  Doctors, dieticians, and other experts agree that there’s simply no magic non-prescription pill that will allow you to block the absorption of fat, carbs, or calories. The key to curbing your craving for those “downfall foods” is portion control. Limit yourself to a smaller serving or a slimmer slice.
• “Lose 30 pounds in 30 days!”
  Losing weight at the rate of a pound or two a week is the most effective way to take it off and keep it off. At best, products promising lightning-fast weight loss are false. At worst, they can ruin your health.
• “Everybody will lose weight!”
  Your habits and health concerns are unique. There is simply no one-size-fits-all product guaranteed to work for everyone. Team up with your health care provider to design a personalized nutrition and exercise program suited to your lifestyle and metabolism.
• “Lose weight with our miracle diet patch or cream!”
  You’ve seen the ads for diet patches or creams that claim to melt away the pounds. Don’t believe them. There’s nothing you can wear or apply to your skin that will cause you to lose weight.

Source [2]