Heidi's Klum's catchphrase -- "One day you're in, and the next day you're out" -- applies as much to food as it does fashion. Over the years, we've all had favorite eats hit the healthy-food blacklist, but thankfully, some of them are making a return. In fact, recent research has not only redeemed once-taboo foods such as steak, eggs (yolks included), and peanut butter but also found that when eaten in moderation, some of them may actually help you conquer the scale.
Then: Yolks were considered tiny cholesterol bombs.
Now: Numerous studies, including one in a 2011 issue of the European Journal of Clinical Nutrition, have debunked the link between eggs and heart disease. Although a single yolk contains nearly the recommended daily limit for dietary cholesterol, it is the most nutrient-rich part, packed with zinc, iron, vitamins A and D, and choline, which may help reduce breast-cancer risk. Plus, the yolk contains nearly half of an egg's hunger-quashing protein, which is why white-only omelets aren't as satisfying.
"Because you feel full, you're less likely to overeat later on," says Nikhil V. Dhurandhar, Ph.D., an associate professor at Pennington Biomedical Research Center in Baton Rouge, Louisiana.
Bring it back: A hardboiled egg makes a great snack with staying power -- and has only around 70 calories. Just beware fattening companions that often accompany eggs, such as butter, bacon, and cheese.
Then: Higher in calories than most fruits, bananas were considered carbs that packed on pounds.
Now: Bananas contain a type of dietary fiber known as resistant starch that your body can't absorb, so it fills you up temporarily without the risk of filling you out permanently. Other research has linked resistant starch to an increase in post-meal fat-burning, says Janine Higgins, Ph.D., nutrition research director at the Colorado Clinical and Translational Sciences Institute. One of the by-products of the unabsorbed carbohydrates in your system is butyrate, a fatty acid that may inhibit the body's ability to burn carbs, forcing it to incinerate fat instead.
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Bring it back: Choose a greener banana; once it has turned totally yellow, the starch inside has broken down and is no longer resistant to digestion. If you don't like to eat bananas when they're that firm, toss one into the blender for a hunger-dampening smoothie. And take a deep whiff before sipping it: Research from The Smell Taste Treatment and Research Foundation in Chicago shows that the smell of banana helps reduce appetite, so you may not want to eat as much anyway.
Then: Because it's high in saturated fat, coconut oil was demonized by dieters.
Now: Turns out, coconut oil is swimming in medium-chain triglycerides, fats that can be metabolized faster than the long-chain variety found in other oils like sunflower. "They're rarely stored as fat because the body prefers to use them for energy," says Jonny Bowden, Ph.D., author of The 150 Healthiest Foods on Earth. A 2009 study in Lipids found that supplementing women's diets with about two tablespoons of coconut oil per day fueled a reduction in abdominal obesity while helping elevate HDL (good) cholesterol levels. (Other studies have confirmed there is no negative impact on LDL cholesterol or blood pressure.)
Bring it back: Because coconut oil is calorie dense -- about 120 calories per tablespoon --you still want to watch how much you down. Bowden suggests swapping oils high in omega-6, like corn or vegetable, for virgin or extra-virgin coconut oil.
Then: Beef had a reputation for contributing to heart disease and wide waistlines.
Now: New research suggests that saturated fat—at least in moderation—may not be the evil heart attacker it's been made out to be. And today you can buy cuts of meat that are leaner than what was available a decade ago. Red meat is a stellar source of satisfying protein, a known ally in weight management. "It requires more time and energy to digest and can help you gain metabolically active muscle, which burns more calories at rest than fat does," says Wendy Bazilian, D.P.H., R.D., author of The SuperFoodsRx Diet. Plus, particularly the grass-fed variety contains high concentrations of conjugated linoleic acid (CLA), which is associated with a lower body-fat percentage. Early research indicates that CLA may disrupt enzymes that help deposit and store fat.
Bring it back: The cut of beef is the deciding factor. Extra-lean ones include top sirloin select, sirloin tip, top round, and eye of round roast. They all have fewer than five grams of total fat and two grams of saturated fat per three-ounce serving, but avoid anything labeled prime, which tends to be fatty. Shoot for a three-to four-ounce portion—the size of a BlackBerry—and grill, roast, or bake it (panfrying only soaks it in butter or oil).
Then: This sandwich staple has been shunned as high-fat and high-cal.
Now: True, peanut butter contains 16 grams of fat per two-tablespoon serving, but it's the heart-healthy, monounsaturated kind. "Peanut butter helps with appetite regulation without your even trying," says Bazilian. "It's so nutrient dense that we simply end up consuming fewer calories overall." A study in the International Journal of Obesity found that people who remained on a diet that included peanut butter for 18 months lost an average of nine pounds.
Bring it back: Skip reduced-fat varieties, which are often heavily sweetened to compensate for missing flavor. Stick with natural PB with no added sweeteners and focus on portion control. If you can't be bothered to measure out two level tablespoons, buy individual packets (try Justin's) for 200 calories or fewer.
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