Runway model Petra Nemcova and reality star Bethenny (not-so-ever-after) Frankel have both confessed to using laxatives to get super-skinny.

That's something that around 17 million Americans have done, too - including teenage kids in sports (like wrestling), and seniors who get hooked while trying to relieve chronic constipation.

It's super risky because your body stops being able to move food through your intestines on its own, and you're purging vital nutrients. Your heart and kidneys suffer; when you stop, there's usually a big weight gain from fluid retention. Not such a good deal.

For weight loss, laxatives are never appropriate. Best bet for losing weight without losing essential nutrients? Shed one pound a week by increasing your physical activity (aim for 10,000 steps a day) and cut out all trans fats and most saturated fats, all added sugars and sugary syrups, and any grain that isn't 100 percent whole.

For occasional constipation, our laxative of choice is the Double F-bomb - the fruit and fiber bomb, that is! Dish up 2 ounces each of cherries, raisins, apricots and prunes (it's known as the CRAP diet). And up your fiber intake with 100 percent whole grains, fresh and frozen veggies, apples and psyllium husks. We take a little bit of psyllium husks mixed into our green drink at the start of every meal. You're heading for 25 grams of fiber a day. If you get your fiber all at once, you're likely to have cramps, so eat and drink a little throughout the day. Laxatives have their place, but let a doctor suggest them.

Mehmet Oz, M.D., is host of "The Dr. Oz Show," and Mike Roizen, M.D., is chief medical officer at the Cleveland Clinic Wellness Institute. To live your healthiest, visit sharecare.com. Distributed by King Features Syndicate, Inc.