Consumer Diet Guide: Sizing Up America's Most Popular Diets

Experts weigh in on the pros and cons of each plan.
By Laurie Pawlik-Kienlen for MSN Health & Fitness

The key to losing weight—and keeping it off—is to find the eating plan that fits your personality and lifestyle. To help, we've rounded up expert opinions on the pros and cons of the 10 most popular diets in America.

"All the popular diets can help you lose weight because they provide almost identical calorie intakes," says nutritional biochemist and author Shawn Talbott, Ph.D. "But different people may do better on different diets because of personal tastes. For instance, if you love bread, don't even think about trying Atkins … because it won't work."

Here's a look at the 10 most popular diets in America:

Jenny Craig
Tasty, ready-made meals and snacks—"Jenny's Cuisine"—are perks of Valerie Bertinelli and Queen Latifah's favorite diet (which is similar to NutriSystem). Amy Hendel, health expert and author of Fat Families, Thin Families (Benbella Books, 2008), sums it up: "No thinking, just eating."

Pros: Jenny Craig is a balanced, calorie-controlled diet with weekly consultations in person or by phone.

Cons: Jenny's Cuisine gets expensive (though a short-term stint could teach portion control). "Average people aren't under the same scrutiny as the celebrities who lost tons of weight, so the pressure to stay on track is decreased," says Hendel. In addition, participants may tire of the prepared meals and may not learn how to count calories outside the program.

Mediterranean Diet
Rather than focusing on calories, this healthy eating plan revolves around veggies, whole grains, olive oil, nuts, fish, poultry, and dairy—with limited red meats and moderate wine consumption.

Pros: The home cooking emphasis makes it inexpensive and easier to track fats, cholesterol, and sodium, says Hendel. Plus, these flavorful foods don't trigger feelings of deprivation. Nutritionist Haruko Oyama of Montefiore Medical Center says this diet is connected to numerous health benefits, such as decreased risks of cardiovascular disease, and possibly diabetes and Alzheimer's.

Cons: "The effect of the Mediterranean Diet on weight loss specifically hasn't been as widely researched as the health effects," says Oyama. Plus, people could take the freedom to eat healthy fats a little too far—and overdo it.

Zone Diet
You won't overdo it if you stay in the Zone: one gram of fat for every two grams of protein and three grams of carbohydrates, meant to balance hormones and control hunger.

Pros: New York City-based nutritionist and personal trainer Ariane Hundt says, "This diet promotes fat loss, reduces inflammation, increases energy, reduces cholesterol, and has anti-aging benefits." Plus, nutritionists generally favor healthy, balanced meals.

Cons: "The fat, protein, [and] carb groups are a little simplistic," says Hendel. "We need some calcium from dairy every day, and we need to separate grain-based carbohydrates from fruits and vegetables (the Zone counts them as one). And, limiting grains can be difficult to do over the long term. Most Zone-committed eaters seem to be highly motivated, physically active people who can afford the home-delivered meals."

Weight Watchers

This diet giant also sells its own pre-made meals plus books and magazines, and recently introduced the new Momentum program, replacing the traditional Flex and Core plans. Momentum revolves around the POINTS system and offers strategies for overcoming temptations. Diet coach Laurie Beebe, R.D., says, "Weight Watchers is effective because people can stay on it for years and keep the weight off."

Pros: Regular meetings offer information-driven discussions, weigh-ins, tools such as food tracking journals and activity calculators, and encouragement—plus Weight Watchers provides online support. Beebe confirms that the portion control, controlled calories, and accountability help people lose weight.

Cons: Each meeting costs about $10 (depending on your area), tools cost extra, and the POINTS system doesn't necessarily reflect the nutritional value of food.

Volumetrics
In this plan, nutrient-dense foods full of fiber, vitamins and minerals are encouraged (such as veggies, fruits, broth-based soups, nonfat milk, etc.), while energy-dense foods are in the no-fly zone (cheeseburgers, cookies, packaged foods, etc.).

Pros: It's a healthy, inexpensive way to lose weight. "Diets often fail because people feel hungry," says dietician Jodi Greebel, author of The Little Black Apron: A Single Girl's Guide to Cooking with Style and Grace (Polka Dot Press, 2007). "Volumetrics encourages large quantities of nutrient-dense foods, which fill you up. This plan also encourages food journals and exercising—two keys to permanent weight loss."

Cons: "Volume alone may not satisfy your taste buds," says Hundt, potentially leaving you vulnerable to those tempting fat, sugar, and salt cravings.

The Flat Belly Diet
Liz Vaccariello, editor-in-chief of Prevention magazine, co-wrote the book about this female-focused, Mediterranean-style diet. The claim: Eating monounsaturated fatty acids (MUFAs) at every meal will flatten bellies without exercise. Meals are capped at 400 calories, foods that lead to bloating are discouraged, and participants are told to eat every four hours.

Pros: "Eating a specific number of calories regularly will help maintain energy levels, stabilize blood glucose levels, and prevent hunger," says Susan Kraus, a clinical dietitian at Hackensack University Medical Center. "Plus, the recipes are tasty, which keeps dieters satisfied."

Cons: Research doesn't prove that diets target specific body parts, and health experts aren't crazy about de-emphasizing exercise.

Weigh Down Diet
Satisfy your cravings here! "This diet focuses on portion sizes and hunger cues, which are very important for weight loss," says Greebel. All foods are allowed in this Higher Power–based diet; eating is motivated by the body's physical needs.

Pros: Kraus says dieters are encouraged to become more spiritual, stop obsessing about food, and take more responsibility for their eating habits.

Cons: Greebel points out that it's difficult to lose weight if you're not watching what you eat, even if you're careful with portion sizes. Kraus adds that people might need a more specific, structured plan to lose weight successfully.

South Beach Diet
If you need structure, here's one of the strictest diets on the market. Cardiologist Arthur Agatston's diet is divided into three phases: Eliminate Cravings, Lose Steadily, and Maintain. Strict guidelines about reduced-fat dairy, lean proteins, veggies and healthy fats are part of every phase.

Pros: "The core of this diet is a heart-health promoting, balanced diet that most people can follow if they don't mind the rules," says Hendel.

Cons: Dr. Jan Evans, R.D., of Richmond, Va., warns, "The first two phases are unhealthy, unbalanced, and not only cause fluid loss [and] dehydration, but can cause ketosis and electrolyte imbalance. The diet is too restrictive in the first two phases, and lacks essential nutrients."

Atkins Diet
Exercising is essential for losing weight—and so is eating a balanced diet. Similar to the Scarsdale diet that rose to fame in the late 1970s, the Atkins plan focuses on increased protein intake and limited carbohydrates.

Pros: "These very low carb diets can quickly and dramatically shed pounds," says Hendel. "Water weight goes first, then fat."

Cons: Low-carb diets have a bad rap in the medical community because of the potential long-term health effects of excess protein: high cholesterol, kidney abnormalities, cancer risks, unhealthy metabolic states, and osteoporosis. Atkins now includes more plant-based foods than when it was first introduced, though many nutritionists still deem it unhealthy. "Most people simply cannot sustain eating this much protein," Hendel says. "I've also smelled the sweat and breath odors of people on long-term high-protein diets, and it's a bit offensive."

Sugar Busters Diet
This reduced-carb eating plan is similar to Atkins, but not as intense. The diet focuses on elimination of simple carbs like potatoes and white bread, and simple sugar foods like candy and sugary cereals.

Pros: "This diet steers clear of sugar-laden processed foods," says Hundt. "Natural foods—lean proteins, good fats, vegetables and whole grains—are emphasized, resulting in balanced blood sugar levels, increased fat burning, and a healthy lean body."

Cons: A potential drawback of this reduced-carb diet is increased protein consumption, which may have negative health effects in the long run. Steering clear of sugar is an excellent way to lose weight, but choosing a healthy balance of proteins, carbs and fats is also important.

And, here's one bonus eating plan to chew on:

The Maker's Diet
This diet is based on Biblical and scientific principles. It encourages dieters to observe God's dietary laws and attack the three I's: insulin, infection and inflammation. Fasting, supplements, cleansing agents, and kosher practices are promoted—making this diet less appealing to the general population.