Have you ever gone on a diet? If you have, you're not alone! You and 45 million of your closest friends go on a diet each year. Americans spend about $33 billion on weight loss products, yet two-thirds of adults are still overweight or obese.

Diet is one of the most important influences on health. Optimal eating is associated with increased life expectancy and dramatic reduction in lifetime risk of all chronic disease.

There are dozens of types of diets, including low-carb, high-protein, vegetarian/vegan, paleo, formal programs such as Jenny Craig and Weight Watchers, raw foods, and more. In part one of this series, we looked at which of the popular diets seem to produce the best and healthiest results. In part two, we'll dive into these diets a little further and figure out what we should (and shouldn't) be eating.

Vegetarians tend to have lower body weight, suffer less from disease and have a longer life expectancy. Most vegetarian diets are low in or devoid of animal products. They’re also usually lower than nonvegetarian diets in total fat, saturated fat and cholesterol. Many studies have shown that vegetarians seem to have a lower risk of obesity, coronary heart disease (which causes heart attack), high blood pressure, diabetes mellitus and some forms of cancer.

Vegetarian and vegan diets can be healthful and nutritionally sound if they’re carefully planned to include essential nutrients. However, a vegetarian diet can be unhealthy if it contains too many calories and/or saturated fat and not enough important nutrients.

High-protein diets include popular diets such as Atkins, South Beach, and Zone. While high-protein diets can help preserve lean body mass during weight loss, they can pose a potential acid load to the kidneys. If you are on a high-proten diet, you are advised to choose the source of your protein carefully, including plant-based sources in addition to foods of animal origin. Many red meats, eggs and dairy products contain high levels of saturated fats and cholesterol, which puts consumers at higher risk for heart disease, hyperlipidemia and hypercholesterolemia.

In the paleo diet, the idea is to eat like a cave man or woman. It includes grass-fed meat, fresh seafood, fresh fruits and veggies, eggs, nut seeds, and healthful oils. You'll avoid cereal grains, legumes, dairy, refined sugars, potatoes, processed foods, and refined vegetable oils.

The Mediterranean diet is characterized by cooking style in countries that border the Mediterranean Sea. It includes the use of olive oil, fruits, vegetables, fish and whole grains, and limits unhealthy fats. According to Mayo Clinic, research has shown that the traditional Mediterranean diet reduces the risk of heart disease. The diet has been associated with a lower level of oxidized low-density lipoprotein (LDL) cholesterol — the "bad" cholesterol that's more likely to build up deposits in your arteries.

The DASH (Dietary Approaches to Stop Hypertension) eating plan is designed to help you manage blood pressure. Emphasizing healthy food sources, it also limits red meat, sodium (salt), sweets, added sugars and sugar-containing beverages. In addition to being easy to follow, delicious and varied, the DASH eating plan is proven effective. On the DASH diet, you will eat fruits, vegetables, whole-grains, low-fat dairy products, skinless poultry and fish, nuts and legumes, and non-tropical vegetable oils.

Which one is best?

It depends. Every diet has pros and cons. Are you looking to...

• Lose or gain weight
• Prevent illnesses, such as heart disease or diabetes
• Be more healthy overall
• Protect animals/have a smaller environmental footprint

There is no one perfect diet. A healthy, sustainable eating plan has several common elements:

• Primarily whole foods from nature, not processed foods
• Primarily plants
• Animal foods that are themselves the products of pure plant foods

This means a diet consisting of fruits, veggies, nuts, seeds, beans, soy, and grass-fed poultry or meat. Both the Mediterranean and DASH diets have a lot of these components and are supported by research.

Healthy Eating

Healthy eating includes lots of different kinds of food. It should allow room for your favorite foods in reasonable portions and should be a sustainable way of eating, without being a fad diet. Most of us don't eat enough fruits, vegetables, dairy and oils. We eat diets that are too high in total grain and protein, with too much added sugar, saturated fats, and sodium.

The Bottom Line

A healthy eating pattern accounts for all foods and beverages within an appropriate calorie level:

• Variety of vegetables from all of the subgroups—dark green, red and orange, legumes (beans and peas), starchy, and other veggies
• Fruits, especially whole fruits
• Grains, at least half of which are whole grains
• Fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages
• A variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), and nuts, seeds, and soy products
• Oils
• Limits saturated fats and trans fats, added sugars, and sodium
  • Consume less than 10 percent of calories per day from added sugars
  • Consume less than 10 percent of calories per day from saturated fats
  • Consume less than 2,300 milligrams (mg) per day of sodium
  • If alcohol is consumed, it should be consumed in moderation—up to one drink per day for women and up to two drinks per day for men

About half of all American adults—117 million individuals—have one or more preventable chronic diseases, many of which are related to poor quality eating patterns and physical inactivity. These include cardiovascular disease, high blood pressure, type 2 diabetes, some cancers, and poor bone health.

Next Steps

Want to start eating better? Make small incremental changes, rather than trying to change everything about your current diet. Try adding a serving of plant-based foods to one or more meals a day. Replace unhealthy oils with a healthy alternative, such as olive oil. Have fruit for dessert. Learn what portion sizes actually look like. You're probably eating a lot more than you realize!

Not sure how much you eat or if you get enough healthy foods? Keep a food diary for a week.

Still need help? Talk to your doctor or a nutritionist/dietitian who can help you develop a sustainable, healthy eating plan.