What do Sardinia, Italy; Nicoya Peninsula, Costa Rica; and Okinawa, Japan all have in common? They're home to some of the healthiest, longest-living people in the world. These areas, called Blue Zones, are where Katz recommends we look for healthy-eating inspiration.

While there are differences in each diet, Katz says they have one major similarity: Their diet focuses on whole foods, without any "glow-in-the-dark junk food." Eating wholesome foods in sensible combinations is fundamental to having a healthy diet, says Katz. For example: While broccoli is healthy, a diet of only broccoli isn't healthy. Variety is key.

To adopt a more "Blue Zones" way of eating, don't get caught up in slashing one specific thing from your diet (like sugar, carbs, fat or gluten). After all, a gluten-free cookie is still a cookie.

Instead, Katz says to make better choices with the foods you are already eating. If you're eating Cap'n Crunch for breakfast, switch to a cereal with more whole grains, less sugar and fewer ingredients. Short ingredient lists help you avoid tons of added sugar and salt, and eventually you come to prefer simpler foods that, ideally, don't need an ingredient list at all. This is essentially rehab for your taste buds. "When you prefer it, that makes it sustainable for a lifetime," says Katz.

Food is some of the best medicine. Eating well, in addition to not smoking and exercising regularly, eliminates 80 percent of chronic disease, says Katz. We'll let that sink in for a minute.

In Mexico, lunch is typically the largest meal of the day. Studies show that eating smaller portions for dinner is beneficial to weight loss. Cimperman cites a study in the "International Journal of Obesity" that monitored 420 overweight people and found that those who ate their largest meal before 3 p.m. lost more weight more quickly than those who ate later.

While Cimperman say there could be other factors that contributed, she notes that people's ability to make good food choices decrease after a long, stressful day (we've all fallen victim to post-work pizza delivery). "Also, that big midday meal may help fuel our energy levels thus increasing activity and calorie burn," Cimperman says.

And, despite the common belief that carbs = bad, carbs are good for you -- if you choose the right ones. "Instead of micro-managing timing and quantity of carb intake, focus on choosing whole grains and high-fiber fruits," Cimperman says. "Combine carbs with a little bit of lean protein (low-fat dairy, lean meat/fish, nuts) for a filling meal or snack."

Think about the last time you sat down with your family for a relaxed, hour-long dinner.

Nothing coming to you? You're not alone: Only 28 percent of American families eat dinner together, compared to 92 percent of French families. They also take their time eating, averaging around 42 minutes for a meal (and no, they're not catching up on "Scandal" while eating).

"Food is enjoyed, rather than scarfed down," says Cimperman. "Truly tasting your food helps you be satisfied with smaller portions." She points out that it takes a whole 20 minutes for your hormones to tell your brain that you're full -- eat too fast, and you could be inflicting some serious caloric damage.

But, it isn't just the French diet that keeps them slender. Cimperman notes that there's less reliance on "convenience foods" and they tend to snack less. Staying active also helps -- not just the exercise that comes from going to the gym, but activity that's built into their daily routine (read: they walk everywhere).

Cimperman says that the Japanese diet contains about 25 percent fewer calories than the American diet, thanks to smaller portion sizes and plates filled with veggies. She says to slash portion sizes by simply using smaller plates, and try to fill half your plate with veggies at both lunch and dinner.

If you're sick of your boring steamed-broccoli-and-carrots routine, Cimperman says to experiment with veggies you wouldn't normally pick up, like purple potato, edamame and miso (yes, it's a vegetable not just a type of soup).

Lastly, incorporate fish into your diet at least three times a week (when this writer took a life estimator test via the Blue Zones website, she found she would gain 219 days just by eating more fish). Cimperman recommends fish high in omega-3 fatty acids like salmon and tuna. Omega 3 fatty acids can reduce the risk of heart disease and improve brain health (one study even found that they helped reduce cramps).

Fermented cabbage probably doesn't fall at the top of your grocery list (because, to be honest, eating non-fermented cabbage is already a chore). But kimchi, a traditional Korean side dish, could be just what your gut needs.

Fermented foods contain probiotics -- good bacteria that live in our gut and play a large role in our bodies' immune function; they also impact our weight and our ability to lose weight, says Cimperman.