One step to fighting the obesity battle might just be printed on the back of your food package. New research published in the journal Agricultural Economics suggests that people who read nutrition labels tend to be slimmer than those who don't. And that effect was especially pronounced among women: Female study participants who scanned labels were more than eight pounds lighter than their non-label-reading peers.

Of course, it could be that those who look at labels are already more health-conscious, but it can only help to understand what's really in your food. And while the finding is somewhat intuitive, the truth is that many of us aren't reading those labels. A study published last year in the Journal of the American Dietetic Association found that while a third of people say they always look at the calorie counts on a label, in reality only 9 percent really do. And just 1 percent looked at the other components, including total fat, trans fat, sugar and serving size.

"The results of this study suggest that consumers have a finite attention span for Nutrition Facts labels: although most consumers did view labels, very few consumers viewed every component on any label,” study researchers Dan J. Graham, Ph.D. and Robert W. Jeffrey, Ph.D., of the University of Minnesota School of Public Health, wrote in their findings.

So how can we make label reading more accessible? "There really is so much information on a food label that it can get overwhelming," says HuffPost blogger Dawn Jackson Blatner, R.D., author of "The Flexitarian Diet." "Yes, you can look at everything, but soon one thing starts canceling out the next."

We spoke to Blatner and Toby Smithson, R.D., founder of DiabetesEveryDay.com, to help understand what the different components on the label really mean, and to suss out what you should prioritize when comparing labels in the grocery store. Of course, people with various health concerns (diabetes, high cholesterol, etc.) will have different needs when evaluating a label -- but these guidelines are a good place to start. Take a look, then tell us: What part of the label do you always read?

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  • Serving Size

    "The entire food label is based on one thing, and that's serving size," Blatner says. "It is the most underestimated, under-written about, under-talked about thing on a food label." And so, accordingly, this should be the first thing you look at when scanning the back of a package. Planning to eat all three servings in a bag of pretzels? You'll need to remember to multiply all the numbers below by three. Learn more about <a href="http://www.huffingtonpost.com/2012/08/23/serving-sizes_n_1822551.html?utm_hp_ref=health-problems" target="_hplink">how serving sizes are determined here</a>.

  • Calories (And Calories From Fat)

    Now that two thirds of the U.S. population is overweight or obese, Blatner says calories should be your next stop when evaluating a label. "Calories make the world go round with weight," she says. Forty calories per serving is considered "low," 100 calories is "moderate" and 400 calories and beyond is "high," <a href="http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HeartSmartShopping/Reading-Food-Nutrition-Labels_UCM_300132_Article.jsp" target="_hplink">according to the American Heart Association</a>. Food labels are based on a 2,000 calorie diet -- you might need more or less depending on your age, weight, gender and activity level. For reference, calculate your recommended daily calorie intake <a href="http://www.mayoclinic.com/health/calorie-calculator/NU00598" target="_hplink">by clicking over to the Mayo Clinic</a>, and speak to your doctor for specific recommendations. As for that "calories from fat" line? Skip it, Smithson says. "It's confusing and it doesn't give as much great information as the other parts of the label."

  • Fat (Total Fat, Saturated Fat, Trans Fat)

    In the past, Blatner says, people obsessed about the "total fat" line on the label -- but now we know there are actually <em>good</em> fats we need in our diet, namely the heart-healthy monounsaturated and polyunsaturated fats (found, for instance, in fatty fish). So instead of focusing on the total fat count, look for saturated fats, which raise blood cholesterol levels and increase risk for heart disease and stroke. <a href="http://www.heart.org/HEARTORG/GettingHealthy/FatsAndOils/Fats101/Saturated-Fats_UCM_301110_Article.jsp" target="_hplink">The American Heart Association recommends</a> limiting these fats to 7 percent of total daily calories -- that adds up to 16 grams for someone on a 2,000 calorie-a-day diet. Too complicated? Try the 5 and 20 trick: 5 percent of your daily value is considered low and 20 percent is considered high, anything in between is moderate. So aim for 5 percent or less on the things you don't want (like saturated fat) and 20 percent or more on the things you do. Trans fats are especially dangerous, as they raise your LDL (bad) cholesterol and lower your good (HDL) cholesterol at the same time, <a href="http://www.mayoclinic.com/health/trans-fat/CL00032" target="_hplink">according to the Mayo Clinic</a>. Fortunately, many manufacturers have scrambled to remove trans fat from their products. But Smithson points out that a label can say it has 0 g of trans fat as long as it actually contains .49 grams or fewer -- meaning that if you consume more than one serving size, you might still go beyond the daily limits. Look for the words "partially hydrogenated" on the ingredient label, which is another way of saying trans fat, <a href="http://www.mayoclinic.com/health/trans-fat/CL00032 " target="_hplink">the Mayo Clinic says</a>.

  • Cholesterol

    "Saturated fat is tied even more to your actual body cholesterol levels than cholesterol in food itself," Blatner says, so when doing a quick label scan, you're better off to look for the former rather than the latter. That said, you should still keep the amount of cholesterol as low as possible (5 percent of your daily value or less according to the 5 and 20 rule). And remember that cholesterol only occurs in animal products -- if a bag of peanuts, for instance, is boasting being "cholesterol free," that's no great feat.

  • Sodium

    The average sodium intake among Americans is 3,436 mg a day, <a href="http://www.cdc.gov/features/dssodium/" target="_hplink">according to the CDC</a>, more than 1,000 milligrams above the recommended upper limit of 2,300 mg for the general population. And too much sodium can increase blood pressure and, in turn, risk for heart disease and stroke. Sodium is one stop you'll definitely want to make on the food label, Blatner says. While you might be able to spot a calorie-rich or a carb-heavy food in the store, it can be surprising how many foods contain salt (<a href="http://www.huffingtonpost.com/2012/07/20/how-much-salt-is-in-cereal-cake-ketchup_n_1687403.html" target="_hplink">breakfast cereal anyone?</a>) The 5 and 20 rule definitely applies here -- aim for foods that have 5 or fewer percent of your daily value of sodium. But Smithson points out that those percentages are only based on the 2,300 mg recommended for the <em>general</em> population -- people over age 51, African Americans, and those with high blood pressure, diabetes and chronic kidney disease should curb their intake to 1,500 mg of sodium a day. In fact, those "special populations" <a href="http://www.cdc.gov/features/dssodium/" target="_hplink">add up to the majority of adults</a>, according to the CDC -- and that means you'll need to calculate your own daily values at the store.

  • Total Carb

    Despite their bad rap, carbs are an important nutrient, and a key source of energy for the body. (Complex carbohydrates, which include whole grains, are the healthier pick over refined or simple carbohydrates, <a href="http://www.nlm.nih.gov/medlineplus/carbohydrates.html" target="_hplink">according to the NIH</a>). Carb counting <em>is</em> important for people with diabetes, Smithson explains, as <a href="http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/carbohydrates.html" target="_hplink">carbohydrates raise blood glucose levels</a>.

  • Fiber

    Plenty of dietary fiber is important for maintaining intestinal regularity and bowel health, Smithson explains. Other benefits include reducing blood cholesterol levels and controlling blood sugar levels, and assisting in weight loss, <a href="http://www.mayoclinic.com/health/fiber/NU00033" target="_hplink">according to the Mayo Clinic</a>. <a href="http://www.choosemyplate.gov/faqs.html" target="_hplink">The USDA recommends consuming 14 g of fiber</a> for every 1,000 calories per day, which adds up to 28 g for someone on a 2,000 calorie diet. But no need to do math -- the 5 and 20 rule applies again; shoot to pick foods with 20 percent or more of your daily value of fiber. For a list of surprisingly rich sources of fiber, <a href="http://www.huffingtonpost.com/2012/05/29/high-fiber-foods_n_1543165.html" target="_hplink">click here</a>.

  • Sugars

    <a href="http://www.fda.gov/Food/ResourcesForYou/Consumers/NFLPM/ucm274593.htm" target="_hplink">According to the FDA</a>, there's no percent daily value next to sugar, as no recommendations have been made at this point for how much to eat in a day. But the American Heart Association recommends keeping added sugar consumption to 6 teaspoons a day for women and 9 teaspoons for men. The reality is that the average American is consuming more than <em>22</em> teaspoons a day. So without a percent daily value, you'll have to do a little math on this one. According to WebMD, <a href="http://www.webmd.com/food-recipes/features/sugar-shockers-foods-surprisingly-high-in-sugar" target="_hplink">each teaspoon of sugar is about 4 g</a>. So that means women should keep daily sugar intake at 24 g or fewer a day, and men should stay at 36 g or fewer. But there is a difference between natural occurring sugars, which can be found in foods like fruits and milk, and added sugars. Unfortunately the labels don't divide up the two, so Smithson suggests doing a little sleuthing on the ingredient label to look for sugar (or sugar synonyms, such as high fructose corn syrup, maltose or dextrose -- <a href="http://www.huffingtonpost.com/2012/09/13/other-names-for-sugar-maltose-dextrose_n_1874487.html " target="_hplink">check out our complete list of sugar disguises here</a>).

  • Protein

    <a href="http://www.cdc.gov/nutrition/everyone/basics/protein.html" target="_hplink">According to the CDC</a>, about 35 percent of your daily calories should come from protein -- that's about 46 g for adult women and 56 g for adult men. <a href="http://www.fda.gov/Food/ResourcesForYou/Consumers/NFLPM/ucm274593.htm" target="_hplink">The FDA doesn't require labels to list percent daily values</a> for protein (unless a claim is made that it's "high protein"), as most adults and children consume plenty of the nutrient. Meat may be the most well-known source of protein, but it's definitely not the only option -- for a list of meat-free sources, <a href="http://www.huffingtonpost.com/2012/05/24/vegetarian-protein-sources_n_1539928.html" target="_hplink">click here</a>.

  • Vitamins

    Here comes the good end of the 5 and 20 rule -- aim to choose foods that have 20 percent or more of Vitamin A, Vitamin C, Calcium or iron, as that means they're a good source of the nutrient. Remember that foods within the same category can have widely varying amounts of each vitamin, making comparisons particularly important. Yogurt, for instance, might have anywhere from 15 to 45 percent of your daily calcium requirement, Smithson explains. These nutrients are only expressed in percent daily values on nutrition labels -- aim to get each one to add up to 100 percent. If you're watching calcium intake, you can calculate mg (women under 50 need 1,000 mg a day and women over 50 need 1,200 mg a day for bone health) by adding a 0 to the end of the percent daily value, Smithson says. If something has, say 15 percent of your daily calcium, that calculates out to 150 mg. Some ingredient labels also mention B vitamins, such as riboflavin and thiamin, which she says are less of a concern, as we typically don't have shortages in these. Come to think of it, we've never seen a label brag that it's a "good source of thiamin."