One year butter will kill you and margarine is better. The next it's the other way around. One article claims running will destroy your joints. A second trumpets the news that it strengthens your bones. And all the while, marketing from the food and fitness industries blares unproven claims about their products.

No wonder so many folks with a sincere desire to live healthily are so confused.

Thanks to all this contradictory information, many of us end up believing yesterday's advice or over-hyped trends that sabotage our efforts to stay healthy. In our sedentary, temptation-filled world keeping fit is hard enough. You don't need myths making things even more difficult, so I hunted around the web for some of the most common -- and most damaging -- health beliefs that current science says are actually dead wrong.

1. Avoiding fat

For years fat was public health enemy number one, with doctors and nutritionists warning that your love of bacon and cheese was going to give you a heart attack. But the scientific consensus has changed radically.

"The continuation of a food policy recommending high-carbohydrate, low-fat, low-calorie intakes as 'healthy eating' is fatally flawed. Our populations for almost 40 years have been subjected to an uncontrolled global experiment that has gone drastically wrong," professor Iain Bloom told the Guardian.

The new recommendation is to stress less about the amount of fat you're eating and more about avoiding processed foods in favor of whole ones. Avocados and fish are packed with fat, but they're wildly healthier than chemically manipulated "low fat" snacks.

2. Eating (most) protein bars

The packages of these bars usually tout them as a wonder food. Experts say otherwise. "As convenient as these may seem, most store-bought protein bars are high in calories and sugar and filled with all sorts of weird preservatives and additives. If you really want to have your protein bar (and eat it, too), try finding one with less than 5 grams of sugar and minimal ingredients," reports MindBodyGreen.

"Many protein bars are candy bars in disguise," agrees Muscle and Fitness.

3. Washing with antibacterial soap

Washing your hands regularly is a great way to reduce your chance of catching whatever bug is going around the office. Just don't do it with antibacterial soap. That shouldn't be hard to do as the FDA recently banned most kinds, but in case you still have some lying around here's the lowdown on its nasty side effects.

Not only is the stuff no more effective at preventing illness than regular old suds, but it might also aid in the creation of antibiotic-resistant bacteria, disrupt your hormones, and make your kids more likely to develop allergies. The evidence for all that is preliminary, so don't panic, but given the product has no real benefits, it's better not to risk it.

You probably shouldn't overdo it with the hand sanitizer either. The FDA is currently investigating whether it's effective, as well as examining concerns that Purell and the like could possibly be harmful for pregnant women and children.

4. Hiding from the sun

Sunburns remain bad, and for both aesthetic and health reasons, you don't want to turn into one of those leathery orange super tanners. But getting too little sunlight (especially in the fall and winter) is actually more of an issue for most folks living in non-tropical regions than too much.

Exposure to sunlight help your body synthesize vitamin D, which can assist in the prevention of some cancers, and also helps regulate your sleep and brighten your mood. Plus, reams of research shows that even small doses of time in nature, not only gets you off your butt, but can boost concentration and help you be more productive as well.

So don't skip the sunscreen or bake on the beach for hours at noon, but don't let worries about sun damage keep you indoors all day either.

5. Drinking juices and smoothies

The marketing around juice and smoothies screams that getting your fruits and vegetables in liquid form is a super healthy alternative. Doctors aren't convinced. "Fruit juice isn't the same as intact fruit and it has as much sugar as many classical sugar drinks. It is also absorbed very fast, so by the time it gets to your stomach your body doesn't know whether it's Coca-Cola or orange juice, frankly," Susan Jebb, a Cambridge University expert on the subject explains.

What's a better option? Once again, the best choice is to eat food in its natural form. "If you can, always choose fresh fruit and veg [over juice]. You're going to get fiber, more nutrients and you're likely to have fewer calories," recommends dietician Azmina Govindj. If you're thirsty, just drink water.

6. Avoiding booze entirely

Again, moderation is obviously key, but there's absolutely no reason to swear off a little light drinking if you enjoy a beer or wine now and again. In fact, studies show "that the rich vitamin B6 content in beer can prevent the buildup of homocysteine, an amino acid, high levels of which have been linked to heart attacks," points out Reader's Digest.

Wine provides benefits too. The occasional chardonnay or shiraz promotes heart health, shields against some cancers, and can help keep your mind sharp. Still skeptical? Here are all the details from WebMD. Of course, it you're not a drinker, don't start for the health benefits. That would be silly. But if you enjoy an occasional drink, there's no need for guilt.

7. Keeping a close eye on the scale

Of course being aware of your body, energy levels, and overall feeling of fitness is key to staying healthy. But that's really not the same thing as obsessing over the number that appears on your scale, Dr. Carly Stewart points out on Lifehacker. "Using the scale is not the best way to track the progress of a healthy diet and exercise," she insists.

Why? "The scale treats both fat and muscle the same way - a pound of fat is the same as a pound of muscle. If you're strengthening your muscles during your exercise regimen, you might actually see a small amount of weight gain rather than weight loss, which is not a bad thing. A better way to track the progress of diet and exercise is to monitor how you feel and how you look," Stewart explains.