In the ’80s and ’90s, as Americans embraced “I Can’t Believe It’s Not Butter” and sugary low-fat snack packs, obesity doubled. (As David Katz, founder of Yale University’s Prevention Research Center, says, “There is more than one way to eat badly, and our culture is committed to exploring them all.”) If you haven’t already, go ahead and stop buying foods labeled “fat-free.” Some more wisdom from the top nutritional experts in the US: Media Platforms Design Team Photo by Thinkstock Throw out the low-fat foods in your kitchen.You can go back to eating full-fat peanut butter (the low-fat variety swaps some of the fat for sugar—a trade-off we now know may be worse) and topping your salad with olive oil and vinegar. (Too much sugar’s no good; this is your body on the sweet stuffsr.) Media Platforms Design Team Photo by Thinkstock …with the exception of dairy. Ditch fat-free dairy (especially yogurts that trade fat for sugar—some brands have as much as ice cream). Low-fat dairy is still a good bet, delivering the same calcium and protein for dramatically less saturated fat and fewer calories than the full-fat stuff. Media Platforms Design Team Photo by Thinkstock Make like the GreeksAnd eat plenty of foods loaded with polyunsaturated fats. Research shows that eating polyunsaturated fats leads to gaining less fat and more muscle, compared to eating saturated fats. You know the deal: polyunsaturated fats are the ones in nuts, seeds, and fish. Media Platforms Design Team Photo by Thinkstock Go for balance “It’s all about making informed choices based on your personal preferences,” says Gretchen Vannice, a registered dietitian nutritionist and the author of Omega-3 Handbook. “If you eat bacon a lot, you might choose low-fat yogurt for balance. What you don’t want to do is eat bacon and cheese and butter and ice cream and sausage and mayonnaise all in one day.” MORE: 9 New Facts About Fat We’re Pretty Sure You Didn’t Know