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Popular diets

The answer to the perennial question "What's the best diet for losing weight?" is any diet that you can stick with for a long time. It should be as good for your overall health — your heart, bones, colon, and psyche — as it is for your waistline. It should offer plenty of good-tasting and healthy choices, banish few foods, and not require an extensive and expensive list of groceries or supplements.

Many different weight-loss diets have been in the limelight, from very low-fat diets (such as the Ornish and Pritikin diets) to low-carbohydrate diets (such as Atkins and South Beach) as well as combination diets (such as the Zone). Other trends include calorie-density diets (Volumetrics) and Mediterranean-style diets (such as Sonoma).

Here are short summaries of some of the most popular types, followed by a "bottom line" assessment of their effectiveness.

Books: Dr. Atkins' New Diet Revolution; The South Beach Diet

First published in the 1970s, Dr. Atkins' Diet Revolution launched the low-carbohydrate diet craze, which enjoyed a resurgence in the late 1990s. The diet is a carnivore's dream, focusing largely on high-protein meats and poultry (along with eggs and full-fat dairy products), while banishing most carbohydrates such as bread, rice, and pasta. One popular permutation of the low-carb diet is the South Beach diet, which also restricts carbohydrates but urges people to avoid saturated and trans fats (found in meat and processed foods) and to favor healthier, unsaturated fats (found in nuts and fish). It also allows more whole grains, fruits, and vegetables, making it a more balanced approach.

Rationale. The low-carb eating strategy is based on the biological fact that eating carbohydrates raises blood sugar levels, which triggers an outpouring of insulin from the pancreas. The theory goes a step further, claiming that high insulin levels produce hunger, so people who eat carbohydrates take in more calories and gain weight. The antidote to carbohydrates is fat, which is more satisfying and filling. So, people on a high-fat diet eat less and lose weight. Low-carbohydrate diets also tend to cause dehydration. To make up for the lack of carbohydrates in the diet, the body mobilizes its own carbohydrate stores from liver and muscle tissue. In the process, the body also mobilizes water, meaning that pounds are shed as urine. The result is rapid weight loss.

Does this theory translate into actual weight loss? Yes and no — it depends on the individual and the time period. Some people lose a substantial amount of weight on a low-carb diet, while others lose little, and some actually gain weight. And for those who lose, the effects typically aren't permanent. After a few months, weight loss tends to slow and reverse, just as happens with most other diet types.

The American Heart Association cautions people against the Atkins diet, because it is too high in saturated fat and protein, which can be hard on the heart, kidneys, and bones. The lack of fruits and vegetables is also worrisome, because these foods tend to lower the risk of stroke, dementia (advanced memory loss), and certain cancers. Most experts believe South Beach and other, less restrictive low-carbohydrate diets offer a more reasonable approach.

Bottom line. Low-carb diets work for some people and not others. There's no evidence that their short-term effects produce better long-term weight loss than other diets. Equally important, we know little about the long-term health effects of high-protein, high-fat, low-carb diets.

Books: Eat More, Weigh Less; The Pritikin Principle

Once the main strategy for losing weight, low-fat diets have been shoved aside by the low-carb frenzy. That's not necessarily a bad thing, since neither of the two foundations on which low-fat diets were built — fat makes you fat, and fat is bad for the heart — are very solid. Healthy fats can actually promote weight loss, while some fats are good for the heart and eliminating them from the diet can cause problems.

Rationale. Scores of low-fat diets have been promoted over the years. One of the best known is Dr. Dean Ornish's "Eat More, Weigh Less" plan, which grew out of the cholesterol hypothesis developed in the 1960s and '70s. First, the idea was to cut cholesterol from the diet, because it contributed to heart disease. Then researchers realized that dietary fat has an even bigger influence on heart disease, which spurred the low-fat diet. Dr. Ornish's diet originally focused on preventing heart disease but has switched to emphasize weight loss.

Since fat contains 9 calories per gram while carbohydrates contain 4, you can theoretically double your food intake without taking in more calories by cutting back on fatty foods and eating more that are full of carbohydrates, especially water-rich fruits and vegetables.

Keep in mind that the Ornish plan doesn't stop at a whole-grain, vegetarian, very low-fat (less than 10% of calories from fat) diet, but also includes exercise, stress management, and group support. The related Pritikin Principle (which also first originated in the 1970s) also limits dietary fat to 10% of calories and is largely based on vegetables, grains, and fruit.

Bottom line. Low-fat diets have unquestionably helped some people lose weight and keep it off. They've been dismal failures for others, in part because they tend to be less filling, less flavorful, and all around less satisfying than other eating strategies. They also tend to be fairly restrictive about food choices, which can limit your options when dining out.

Books: Sugar Busters; Glucose Revolution

These diets share some similarities with the South Beach diet in that they don't banish all carbohydrates, just the refined ones.

Rationale. Right-carb diets rely heavily on the glycemic index and glycemic load (see "The glycemic index and obesity"). In theory, foods with a low glycemic load generate small but steady increases in blood sugar that help stave off hunger. In contrast, the rapid increases in blood sugar and insulin that follow consumption of foods with a high glycemic load are followed by equally steep drops that soon get your internal hunger alarm ringing. These plans don't ban carbohydrates. Instead, they embrace "correct" carbs while shunning "harmful" ones. In a nutshell, this means eating plenty of fruits, vegetables, and whole grains, and cutting back or cutting out refined sugars (white sugar, high-fructose corn syrup, honey, molasses, etc.) and processed grains.

Bottom line. In general, right-carb diets promote healthy eating by focusing on fruits, vegetables, and whole grains. But you don't really need to rely on the sometimes contradictory glycemic index and glycemic load tables to tell you that. Plans that prohibit refined sugars also make dieting and healthy eating more complicated than it needs to be. Refined sugars aren't toxic; they just add unnecessary calories.

Books: The Zone; Eat Right 4 Your Type

Compared with low-fat or low-carb diets, these diets are more complex and require more work in terms of figuring out what and how much of specific foods you're allowed to eat.

Rationale. Several diets sell the idea that specific proportions of nutrients or certain combinations of foods are essential to weight loss. If you want to enter "The Zone," you must create meals and snacks that contain 9 grams of carbohydrate for every 7 grams of protein and 1.5 grams of fat (40% carbohydrate, 30% fat, and 30% protein). According to Barry Sears, the scientist who developed it, the diet helps control the body's production of hormones such as insulin, but there's no clear evidence to suggest this is true or whether it aids weight loss.

The "Eat Right 4 Your Type" diet promotes the wholly unscientific idea that your blood type determines what you should eat, along with how you should exercise, what supplements you need, and what type of personality you have. Following it isn't easy, since you must remember lists of "good" and "bad" foods. It isn't balanced, something you can tell from the long list of recommended supplements. And it makes it hard to prepare meals for a family with several different blood types.

Bottom line. Proper proportions or correct combinations force you to focus on what you are eating, which helps most people eat fewer calories each day. That's where any weight loss from these diets comes from, not from any nutritional or physiologic secrets the diet developers have uncovered.

Book: Volumetrics

Rationale. According to this plan, developed by nutrition researcher Barbara Rolls, focusing on foods that fill the belly without adding too many calories may help you shed pounds. Foods with a high water content — such as fruits, vegetables, low-fat milk, cooked grains, beans, soups, and stews — get the thumbs up, while high-fat foods like potato chips get the thumbs down, as do dry, calorie-dense ones like pretzels, crackers, and fat-free cookies.

Bottom line. This strategy helps people lose weight the same way most other diets do — it narrows your choices so you take in fewer calories each day. Whether it has a long-term role for weight control isn't known.

Books: The Ultimate Weight Solution; The Automatic Diet

Some people use food for comfort and overeat in response to sadness, loneliness, depression, or any number of other triggers. Breaking an unhealthy relationship with food can help such individuals lose weight. That's where these and other diets come in.

Rationale. In his The Ultimate Weight Solution, Dr. Phil McGraw offers "seven keys to permanent weight loss" — right thinking, healing feelings, a no-fail environment, mastery over food and impulse eating, intentional exercise, a circle of support, and what "Dr. Phil" calls high-response cost, high-yield nutrition. The plan offers little advice about nutrition. The Automatic Diet uses behavior modification techniques to reprogram the patterns that work against healthy eating.

Bottom line. If you think that your habits, behaviors, and relationships with other people and with food promote poor eating habits or influence your ability to lose weight or maintain a steady weight, then a behavioral approach makes sense. Combining it with a healthy eating pattern based on sound nutrition would be even better.

Books: Eat, Drink, & Weigh Less; The Sonoma Diet

Just as there are "good carbs" and "bad carbs," there are good fats and bad fats. These diets emphasize good fats and good carbs.

Rationale. Saturated fat, trans fat, and cholesterol are the bad guys. Good fats are monounsaturated (found in olive oil, for example) and polyunsaturated (found in such foods as fish, canola oil, and walnuts). The Mediterranean diet advocated by Mollie Katzen and Harvard professor Walter Willett in Eat, Drink, & Weigh Less has a moderate amount of fat, but much of it comes from healthful monounsaturated fats and unsaturated omega-3 fats. It is high in carbohydrates, but most of the carbs come from unrefined, fiber-rich foods with a low glycemic index. It is also high in fruits and vegetables, nuts, seeds, and fish, with only modest amounts of meat and cheese.

Bottom line. People living in Mediterranean countries have a lower than expected rate of heart disease. But the traditional lifestyle in the region also includes lots of exercise, regular meal patterns, and wine. It's hard to know what relative role these different factors play — but there is some evidence that in and of itself, the diet can reduce cardiovascular risk.

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The diet studies

What do scientists say about how the different diet plans compare? The results of studies often suggest that it's not the diet plan but whether you stick with it that makes the difference. For example, in a 2005 study published in the Journal of the American Medical Association, researchers randomly assigned a group of 160 overweight and obese adults to one of four popular diet plans: the Atkins diet, the Ornish diet, Weight Watchers, and the Zone diet. After one year, nearly half of the participants had dropped out of the study. But those who completed the study lost similar amounts of weight (about 5 to 7 pounds each, on average). They also lowered their blood levels of cholesterol and several other markers linked to heart disease and diabetes to a similar degree. People assigned to the Atkins and Ornish diets were more likely to drop out of the study, suggesting that many people found these plans too extreme. But for certain people, the structure of a restricted plan may be helpful.

A similar study, published in the British Medical Journal in 2006, compared four programs: the Slim-Fast plan (a meal-replacement approach), Weight Watchers, the Atkins diet, and Rosemary Conley's "Eat Yourself Slim" low-fat diet and fitness plan (which includes a weekly group exercise class). All the diets helped people shed pounds and fat, but many — more than half of the participants — dropped out of the study after eight weeks. About 45% of people in the Rosemary Conley and Atkins groups who completed the six-month study lost 10% of their body weight. For the Weight Watchers and Slim-Fast groups, success rates were slightly lower: only 36% and 21%, respectively, lost 10% of their weight.

Another line of evidence about effective weight-loss strategies comes from a few carefully controlled trials in which volunteers with obesity were blindly assigned to either a standard low-fat diet or a low-carb, high-protein diet. Over all, these trials showed that a low-carb, high-protein diet leads to quicker weight loss than a low-fat diet. In the studies that lasted for a year or longer, though, weight loss was about the same regardless of diet type. These studies focused primarily on weight, and were too short to track other important consequences of diet, such as heart disease, diabetes, bone strength, and cancer.

The overall results mask some startling individual differences. In one trial, on both low-carb and low-fat diets, some people lost weight while others gained. In the low-fat group, the range was from 53 pounds lost to 31 pounds gained. In the low-carb group, it was from 65 pounds lost to 18 gained.

The take-home lesson is that it is okay to experiment on yourself. If you give a diet your best shot and it doesn't work, maybe it wasn't the right one for you, your metabolism, or your situation. Don't get too discouraged or beat yourself up because a diet that "worked for everybody" didn't pay off for you. Try another.

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Review Date: 2006-09-01

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