Why are restaurant portions so large

3 food myths, stop believing now

With healthy eating advice changing so frequently, many people wonder what foods are best for their bodies. Check out these latest food myth busters to see why you need to read past the headlines when it comes to choosing smart foods.

Red meat is bad for your heart. Truth or myth?

MYTH! The bad reputation for red meat comes from huge portions and fatty cuts of beef, which are not only popular but are in demand by many consumers. Restaurant servings have grown so large that a standard serving - about a quarter of a pound (4 ounces, the size of a deck of cards or computer mouse) - looks tight by comparison.

Madelyn Fernstrom breaks myths about red meat, red wine, potatoes

May 10th, 20163: 37

However, with more than 25 portions of lean and extra lean beef, which has much less artery-clogging saturated fat, making healthier choices is easy. Look for "sirloin" and "round" on the label and mixes of at least 90/10 percent (lean / fat) for ground beef. Do your own visual test to limit red meats with the most saturated fat - if you can see a lot of fat in the meat and a greasy band around the outside, skip it, except for special occasions.

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A 4-ounce serving of lean flank steak has about 30 grams of complete protein, 9 grams of fat, 4 grams of saturated fat, and 220 calories, while the same serving of low-fat porterhouse steak is similar in protein, but three times more fat and saturated fat, and 340 calories . And a typical serving of porterhouse steak is at least half a pound (8 ounces) with 680 calories, 50 grams of fat, and 20 grams of saturated fat - about all your fat and saturated fat for the day.

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Another healthy option can be 100 percent grass-fed beef, with a healthier fat profile - less saturated fat compared to grain-fed beef - due to what the cow is feeding. It's more expensive because the cows are fed grass (the natural choice for cows) rather than grain. While expensive beef is grass-fed, it's super flavorful, so smaller servings are more satisfying. As with all red meat, stick with the leaner cuts for optimal health benefits.

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Choosing organic red meat doesn't automatically guarantee a healthier choice. It means the cow was fed organic grain, but not necessarily grass (unless it's labeled). So if you don't choose a lean cut, you are still getting the same amount of saturated fat as you would with a traditional cut.

While fish, poultry, and plant-based sources (like soy and lentil) can also meet your protein needs, you can choose red meat as part of a healthy diet IF you make smart cut and portion size choices.

Potatoes encourage weight gain. Truth or myth?

MYTH! From french fries to baked “loaded” versions, potatoes are the perfect carrier for fat and salt in many delicious forms. But you might be surprised to learn that a potato - white or sweet - can be a nutrient-dense, calorie-controlled vegetable if you make wise choices.

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With every potato, size is important. Even a simple baked potato can have a meal of calories if too large, which is seen in many restaurants and sold as "restaurant size" in supermarkets. A "medium" baked potato (which is still quite strong - at about 7 ounces and a 3-inch diameter) has about 160 calories and is packed with nutrients. With 4 grams of fiber (about 20 percent of your daily count), 4 grams of protein, half your vitamin C for the day, 25 percent of your potassium, a third of your vitamin B6, and nearly 10 percent of your iron, it's a nutritional powerhouse. And a serving size can be half a potato, for half the calories.

While both white and sweet potatoes are nutrient-dense, it is a mistake to believe that frying sweet potatoes is a healthier or lower-calorie option than fried white potatoes. Try "baked" white or sweet potato "fries" or add low-calorie toppings to a baked potato, including salsa, chives, or a tablespoon of low-fat sour cream, Greek yogurt, or cheddar.

Potatoes can be part of a healthy diet, including one for weight loss. Make a side dish of potatoes that make up about a quarter of your entire platter. Whether you're baking, cooking, or microwaving, keep the skin on to optimize the nutrients and fiber.

Drinking red wine is good for your heart. Truth or myth?

MYTH! When it comes to the potential health benefits of alcohol - including wine - serving size and frequency are most important. Only if national guidelines for wine or alcohol consumption are complied with can positive health relationships be found. Remember, the size of a drink is defined by ounces, not the size of the glass. A drink is 5 ounces of wine, 12 ounces of beer, and 1.5 ounces of liquor. The recommended limit is up to two drinks per day for men and up to one for women. Higher consumption is often associated with health risks.

Evidence of wine's health benefits can be found by searching for links - or associations - with wine consumption and health. Studies are most common self-disclosure consumption surveys of thousands of people, received over many years. And these associations are largely positive, although the reasons remain unknown. One theory is that because red grapes contain a compound called "resveratrol" in the skins, that component has been linked to potential beneficial health effects. Perhaps other antioxidants in grapes also contribute. But these are not cause and effect results, and many other factors could contribute.

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In fact, other data shows that alcohol of all types is moderately associated with better health, suggesting that moderate alcohol consumption alone has beneficial health effects.

Red wine is not a healthy food, so if you aren't already consuming wine or alcohol, don't add it as a potential health booster. And if you're not a wine drinker and prefer beer or white wine, it's unclear whether there is an added health benefit. When enjoying red wine, watch out for the recommended serving size and daily limit to optimize health benefits.

Madelyn Fernstrom, Ph.D is NBC News health and nutrition editor.