Experts set the record straight on some of the top weight-loss myths of the last 30 years


Full disclosure: I have experimented with most (though not all) of these popular weight-loss methods: from an all tuna plan in 7th (!) grade to the college era diet that allowed me to consume as many Snackwell cookies and Heinekens as my heart desired. Then there was the "caveman" diet I tried with my husband, a fan of the workout that espouses it. This left me craving white carbs so desperately I was ready to stuff a bagel into a baguette and call it a bagel/baguette sandwich. And eat it.

And yes, many of these diets worked (not counting the beer and cookies)… at first. The reason, say experts, is that any time you drastically change your eating habits-in any way-you're going to see results on the scale. The problem is sustainability. "If you can't envision sticking with a diet for the rest of your life, then it's not a good eating plan," says Janet Brill, R.D., Ph.D., a consultant in private practice and author of Cholesterol Down. We asked Brill and Nicolette Pace, R.D., CDE, about nine of the most popular dieting myths of the last 30 years-and why they're more hype than help.

You Should Eat by Your Blood Type


Whether you're A, B, A/B, or O, the theory goes that depending on your blood type, you should adhere to one of four possible eating plans: low carb/high protein, low fat, vegetarian, or just an overall balanced diet. The reasoning is based on biochemistry and evolutionary theory and, according to both Pace and Brill, has no scientific proof whatsoever.

"Blood type has to do with receptors on red blood cells and doesn't dictate what you should or shouldn't eat," Brill says. If you match your diet to one of the blood type plans and lose weight, the reason is because of a sudden change to your diet or drop in calories, not because you're a universal donor.

You Can Lose Weight by Eliminating Carbs (or Any One Nutrient)


If only this was actually true. Just cut out all carbs/sugar/fat (and eat as much as you want of everything else) and voila, the weight melts off. The problem, Brill says, is that when you cut out one nutrient entirely, you're likely to compensate with another. So if you eliminate all fat from your diet, there's a good chance you'll amp up the carbohydrates, and often the white processed variety. Or if you cut carbs, you may end up eating more fat. And while sugar doesn't have much nutritional value, vowing to let nothing sweet pass your lips is just a recipe for a binge.

"Good carbs and healthy fats are part of a balanced diet, and have loads of health benefits. It's absurd to sacrifice either, and it's not a realistic way to eat for life," Brill says.

Eating the Same Food 24/7 Will Make You Slim


Seventh grade, as everyone knows, is a social minefield of cliques, mean girls, and pre-adolescent insecurity-and in an effort to lose the extra three pounds I was carrying, I decided to eat plain tuna fish for breakfast, lunch, and dinner every day until I could fit into a smaller pair of Gloria Vanderbilt jeans. That lasted through lunch.

Sub in any singular food and you have a weight-loss method that's ebbed and flowed in popularity over the years; for example, the all fruit diet and the notorious cabbage soup diet. There are myriad reasons this is a wrong-headed approach to weight loss, Pace says, but the main one is of course sustainability-forget keeping this up for life (imagine if, 31 years later, I was subsisting solely on canned tuna). Few can maintain this approach for longer than a day.

Avoid Wheat, Lose Weight!


Gluten-free eating-cutting out all wheat-based products-is all the rage, and according to Brill and Pace, utterly pointless unless you have a diagnosed wheat sensitivity or celiac disease (an intolerance to gluten), and then it's more likely that you would have lost weight due to the unpleasant symptoms (like diarrhea) this condition can cause. If you notice any weight loss on a wheat-free diet, it's because you've probably cut back on starch-and by extension calories. The rest is hype.

You Should Separate Your Protein and Starches


I knew a guy-a skinny guy, oddly enough-back in my 20s who was a zealot about food combining, a popular diet method in the 80s and 90s. Though he had zero nutritional education, he was emphatic in his belief that your stomach releases a variety of enzymes, each responsible for digesting a particular nutrient. Eat certain foods together-protein and starches, for example-and apparently you'd wreck some sort of digestional havoc that keeps you from optimal weight and health.

According to Brill, this just isn't how digestion works. "Digestion begins in the mouth the minute you start chewing, as saliva begins to break down food," she explains. "Once it hits your stomach, acid is released that doesn't distinguish between nutrients but goes to work packing food into smaller and smaller particles so nutrients can be absorbed into the bloodstream and waste can make its way through your digestional tract." Plus, notes Pace, certain foods work in concert, boosting absorption of nutrients.

Eat Like Your Ancestors


While the basics of diets like Paleo and the Warrior Diet before that are sound-eat only whole, unprocessed foods-the rules are often random and not something that a caveman or woman would have followed: you can eat sweet potatoes but not white, and butter but only if it's clarified. And besides, who is to say our cave-dwelling forbearers were healthier (no one probably lived past 30)? In fact, archeological findings show that humans evolved and our brains became larger when we started to cook and turn grains into food.

Just Drink Your Diet


If you're of a certain age, or just obsessed with Oprah, you may remember the day she wheeled 60 pounds of fat onto the stage (to represent her 60-pound weight loss), wearing a pair of chic, high-waisted Calvin Klein jeans. Her secret? Months spent on an all-liquid diet known as Optifast, during which time not a single morsel of food passed her lips. Unfortunately she gained back every single ounce as soon as she started eating real food again. If you want to try a juice fast for a few days to jumpstart your diet, go ahead (though Brill recommends this only under medical supervision and notes that it's likely only water weight you've lost). Ultimately, your need to chew will always win out.

A Single Nutrient Has Magic Weight-Loss Powers


Add one specific nutrient to your diet-typically a healthy fat-and poof, goodbye belly fat! The problem, Brill says, is there's just not enough scientific proof to back this up. "Generally these types of diets are healthy, since they're often based on the Mediterranean diet, but there's no real proof that one single nutrient, however healthy, can actually target and reduce fat," she says.

Plus, there's still the matter of calorie control-you can't just load up on healthy fats and expect to lose weight. The issue really is about balance: getting enough of the right types of nutrients rather than favoring one over the other is what helps your body function properly.

Eating Baby Food is a Perfectly Sane Way to Lose Weight


If you are a grown adult, there is one reason that you should have baby food in your possession: you have a baby. OK, maybe if you just underwent a serious surgical procedure and can only stomach pureed food; otherwise eating like an infant doesn't provide adequate protein or flavor (Ever tried it? There's a reason babies are always spitting out the strained peas). And do you really want to go to work with a day's supply of Gerber in your purse to lose five pounds?