It seems like every few years, a new diet grabs headlines, proclaiming itself as a weight loss panacea. First it was fat-free everything; oil was evil, and bagels, plain pasta, and salads with a squirt of lemon juice were all the rage. Next, high-protein diets hit the scene, and meat reigned supreme (but a bun on your burger was dietary suicide). Mediterranean, 40/30/30, vegan—all have had their place at the head of the table.

But a breakthrough 2008 study in the New England Journal of Medicine surprised dieters and doctors. Researchers found that after two years, obese subjects on a low-fat diet had lost just 7 lbs. on average. Those on a Mediterranean diet, characterized by high levels of healthy fats, fruits, and vegetables, lost about 10 lbs., and those on a low-carb diet lost the most weight, about 12 lbs. Researchers also discovered that a low-fat diet conferred the fewest overall health benefits; Mediterranean diet subjects were most likely to have improvements in blood sugar levels; and low-carb followers boasted the most improvement in cholesterol levels.

When it comes to choosing the right plan for you, be sure to discuss all of your options with your healthcare provider. To help you get started, here are some of the most common plans.

Low-carbohydrate/high-protein plans

Cardiologist Robert C. Atkins started the low-carb craze in the 1970s. The Atkins diet limits carbohydrates while emphasizing protein and fats. Followers cycle through various phases during which they consume between 20 and 100 grams of carbohydrates a day, far fewer than the 225 to 325 grams per day recommended by the Institute of Medicine. The South Beach Diet is another popular low-carb weight loss program, which cardiologist Arthur Agatston created in 2003. Adherents are permitted to net about one-third of their daily calories from carbohydrates.

Because many fruits and starchy vegetables are high in carbohydrates, low-carb diets typically prohibit them, along with bread, grains, beans, potatoes, and rice. Sugar is also severely restricted. A typical menu might include a cheese omelet cooked in butter, a “wrap” consisting up deli meat, cheese, and mustard wrapped in lettuce, or a big spinach salad topped with chicken or steak, goat cheese, mushrooms, and full-fat salad dressing.

How can you lose weight eating steak and eggs? The theory behind low-carb lifestyles is that a reduction in dietary carbohydrates leads to lower insulin levels, which causes the body to burn stored fat for energy. Many people will lose weight on a low-carb diet. At first, this is due to water loss; low-carb/high-protein foods often have a diuretic effect. Also, because you are eating large amounts of fat and protein, you will feel full longer. And as with any diet that eliminates or greatly restricts an entire food group, you’ll likely take in fewer calories.

That said, it can be challenging to live without fruit, grains, or sugar. Many people find they lack energy and their workouts suffer as a result. If you replace carbohydrates with protein sources that are high in saturated fat and cholesterol, you may increase your risk of heart disease and certain forms of cancer. Limiting fiber-rich produce and whole-grain foods can lead to constipation and other gastrointestinal problems. Lastly, because low-carb diets force your body into a state of ketosis—where your body burns its own fat, rather than carbohydrates, for fuel—you may struggle with symptoms such as weakness, nausea, dehydration, dizziness, and irritability.

American Heart Association plan

Looking to slim down while also lowering your risk of heart attack and stroke? Try the American Heart Association (AHA) diet, a low-fat plan that targets elevated cholesterol, blood pressure, and body weight. The guidelines promote overall healthy living via clean eating and physical activity. The guidelines include:

  • 5 servings of fruits and vegetables per day
  • 6 servings of grains per day
  • 2 servings of fish per week, preferably fatty fish such as salmon and tuna
  • Reduced-fat dairy products, legumes, skinless poultry, and lean meats
  • Fats with no more than two grams of saturated fat per tablespoon, such as liquid and tub margarine, canola, corn, safflower, and olive oils
  • 30 minutes of physical activity every day
  • Use up at least as many calories as you take in every day, but ideally, try to lower your overall calorie intake by reducing calories in or raising the amount of calories burned per day. To determine how many calories you use in a day, the AHA advises multiplying your current weight by 15 (if you are moderately active). Sedentary individuals (a category into which you likely no longer fall, if you have gotten this far) should multiply their weight by 13 instead of 15.
  • Limit high calorie, low-nutrition foods such as soft drinks and candy, as well as foods high in saturated fat, trans fat, and cholesterol.
  • Keep sodium intake at or below 2,400 mg, or 1¼ teaspoon, per day.
  • Limit alcoholic beverages to no more than two drinks per day for men and one drink per day for women.

If you decide to follow the AHA plan, look for items with a heart and a white check mark at your supermarket. This logo means the item is AHA approved for healthy people over the age of two. However, this plan generally will have you shopping the perimeter of your grocery store. That’s where produce, lean meats, and dairy are typically stored; packaged foods and snacks are in the middle aisles.

Mediterranean-style plans

In the traditional eating patterns of the Mediterranean (Greece, the south of France, Italy, and Turkey), antioxidant-rich fruits and veggies abound, whole grains replace refined white bread, and heart-healthy olive oil—not butter—is the primary fat. And it’s all washed down with a glass of merlot.

For more than 60 years, research has repeatedly confirmed the Mediterranean diet’s ability to lower adults’ risk for cancer, heart disease, and even Alzheimer’s disease. One long-term European study that followed healthy men and women aged 70–90 found that eating Mediterranean-style as part of an overall healthful lifestyle was associated with a more than 50 percent lower rate of death from all causes.

With around 40 percent of its calories coming from healthy fats, the Mediterranean diet is extremely satisfying; it leaves you less likely to binge on high-carb or high-calorie foods. Harvard University researchers have discovered that individuals on a 1,500 calorie per day Mediterranean diet lost more weight than those on a lower fat (20 percent) diet. In fact, some of those on the lower fat diet actually gained weight. The high fiber content, courtesy of vegetables and beans, may also benefit diabetics by slowing increases in blood glucose. In a 2008 British Medical Journal study of 13,000 people, those with greater adherence to a traditional Mediterranean diet were 83 percent less likely to develop type 2 diabetes.

If you choose to follow a Mediterranean diet, you’ll enjoy fatty fish such as wild salmon and mackerel, olive oil, and nuts (important monounsaturated fat sources); fruits and vegetables (think kale, broccoli, cauliflower, and beets); and wine. Mediterranean diet followers tend to eat less saturated fat than those who consume the average American diet.

Vegetarian plans

Just as it sounds, a vegetarian diet restricts animal sources of protein and relies on fruits, vegetables, grains, beans, nuts, and low-fat or fat-free dairy. There are also some divisions within vegetarianism. Lacto-vegetarians prohibit meat, fish, poultry, and eggs; lacto-ovo vegetarians prohibit meat, fish, and poultry; and vegans prohibit all animal products. Research has shown that vegetarians tend to eat fewer calories and less fat than their meat-eating counterparts. As a result, vegetarians tend to have lower body weights than nonvegetarians of similar heights. They reap numerous health benefits as well: A 2009 study published in the American Journal of Clinical Nutrition found “convincing evidence” that vegetarians have lower rates of coronary heart disease, obesity, and cancer, as well as probable lower rates of hypertension and diabetes mellitus.

A proper vegetarian diet includes six servings of grains, five servings of beans, nuts, and other protein-rich foods, four servings of vegetables, two servings of fruit, and two servings of healthy fats per day. But switching to a vegetarian diet does not guarantee weight loss. Many meat-free foods can be high in fat, including cheese, whole milk, and nuts. You’ll likely need to meet with a nutritionist to ensure your calorie and protein needs are being met. Including protein-rich foods is a must, especially because this essential nutrient keeps you feeling satisfied, curbing your appetite and helping you resist the urge to snack. Smart low-fat protein sources include egg whites, beans, low-fat cheese, reduced-fat peanut butter, and soy products. Vegan diets eliminate food sources of vitamin B-12 along with dairy products, so you’ll need B-12 and calcium supplements if you choose this plan.

You likely already enjoy a number of vegetarian meals and snacks: peanut butter and jelly sandwiches, bean burritos, cereal and milk, and pasta with tomato sauce. A good trick for thriving on a vegetarian weight loss plan is understanding how to swap in healthy meat substitutes. For example, prepare your award-winning chili with black beans and squash instead of ground beef. Instead of ordering eggs Benedict at brunch, try an egg white omelet with spinach, basil, and tomato. You’ll also benefit from branching out when dining out. Try Indian food (lentil dal or spicy chickpeas with spinach), Chinese food (veggie stir-fry and steamed brown rice), Japanese food (veggie sushi, miso soup, and edamame), and vegetarian restaurants.

Not ready to go full-throttle vegetarian? You’re not alone. In a 2003 study in the American Journal of Clinical Nutrition, two out of three vegetarians said they feel unable to adhere to a pure veggie diet 100 percent of the time. In response, more and more people are adopting a “flexitarian"—or part-time vegetarian—lifestyle. American Dietetic Association spokesperson Dawn Jackson Blatner, RD, author of The Flexitarian Diet, estimates that the average person could lose up to 30 lbs. by following a flexitarian diet for 6–12 months.