You've most likely seen the late night commercials saying the fat you gain is not all your fault – it’s from pregnancy, stress, a lack of exercise and aging.  And all you have to do is take their pill and the weight will disappear.

Products such as Lipozene and Centrilene have similar commercials touting the same pitch: that you don’t have to change your lifestyle to see a significant weight change.

So what's the truth? Is there evidence to back up these late night advertising claims?

Dr. Kim Edward LeBlanc, Chief of Family Medicine at LSU Health Sciences Center, said some small studies revealed there was some benefit in taking the diet pills.  However, the test subjects in the study were 25-years-old, drank a lot of water and ate low calorie diets.  But there’s a reason why the active ingredient in these products—konjac root—seems offer some benefit: because it's nothing more than fiber.

“It’s very effective at expanding, so it's going to delay the amount of emptying that the stomach has so which gives you a better chance to feel full,” said Dr. Henri Roca, Chief of Integrative Medicine at LSU Health Sciences Center.

According to Roca, fiber can even do more.

“People do tend to lose (weight), they do tend to eat less, it also can lower things like cholesterol, reduces your blood pressure, it is effective at doing that.  It does seem to also be effective at reducing insulin levels, so it can help people with diabetes as well,” Roca said.

LeBlanc added that dieters do not need to count fiber calories because they’re not absorbed into the bloodstream.  They remain in the intestine to aid with digestion.

So if Lipozene and Centrilene are just fiber, should anyone spend $30 a bottle to get more fiber in their diet?

“Fiber is incredibly cheap, you can buy fruit and vegetables and do just as well and they are very tasty and very healthy for you,” LeBlanc said.

It's a basic healthful diet that's high in complex carbohydrates, but there are some warnings before you by these products.  The bulky, high fiber in the pills can also keep some important medications for diabetes, depression and cholesterol from absorbing into the bloodstream, as well essential fat soluble vitamins such as A, D, E and K.  It will not help reduce the stress hormone that makes fat deposits around your waist, and there's also a choking risk.

“It doesn't really dissolve, it forms a gelatinous mass, so if you take a pill people have been known to choke because that pill, if it gets stuck in the esophagus, will then expand,” Roca said.

Doctors said it would be better in powder form, called konjac flour-glucomannin; in fact, some pizza companies use it in baking to add fiber.  But they do add that while most us need more fiber in our diets for good health and to prevent cancer, you have to build up fiber slowly, if not you'll get bloated, gas and stomach distention.

In the meantime, LeBlanc said it’s okay if somebody wanted to use the quick pill rather than nature's more wholesome fiber, but only for the short term.

“If someone wants to use that to jump start their diet or their healthier regimen, I'm all for it I'm not opposed to,” LeBlanc said.  “Anything that's safe and has hardly any side effects that'll get somebody motivated to do some good things for themselves, I'm all for it.”

Doctors said that most Americans only get 15 grams of daily fiber, not enough to promote good health and natural weight loss.  American Diabetes Association recommends 25 to 50 grams of fiber per day, the American Heart Association says 25 grams is okay, and Dr. Roca advises between 35 and 36 grams of fiber.