Diets that promise a quick fix won't keep the weight off long-term, because they don't change your eating habits. Once you reach your goal weight and stop dieting, you're likely to find the pounds creeping back on. Then, if you're like many people, you'll go back on your diet and repeat the same cycle. This is called yo-yo-dieting. Some trendy diets that severely restrict certain food groups may even harm your health. Others are wild cards -- they haven't been studied enough to know what their long-term effects might be.

Quick fixes that rely on diet pills and supplements can be particularly dangerous. Even herbal pills and teas may not be safe because some contain caffeine or other stimulants. Switching to diet colas or Olestra chips to save a few calories won't help in the long run either. Too often, artificial sugars and fats are a crutch to let you continue unhealthy patterns of eating -- and they don't taste as good as the real thing, either. So, what's the answer? To achieve permanent weight loss, you'll need to change the old eating habits and lifestyle that helped put on the pounds in the first place. Some weight-loss programs and diet plans can help, but it's important to be able to tell which ones are healthy and which ones promise more than they can deliver. Here's a review of some of the more popular weight-loss programs and diet plans.

Most plans use a points system of food exchanges to control the total number of calories you eat. Many also rely on their own lines of food to ensure consistent portion sizes and adequate nutrition. This type of weight-loss program will help you lose weight, especially in the short term. However, the limited food choices and expensive pre-packaged foods (and membership fees) keep many people from sticking with the plans for long. One common complaint is that as soon as you go off the diet -- especially if you were relying on the pre-packaged foods -- the weight comes back.

Examples:

•Weight Watchers: This program emphasizes good nutrition and exercise as a way to gradual and long term weight loss. Every food is assigned a certain value, and you're allowed a specific number of points per day. You can also earn activity points (which can be exchanged for food) by exercising. Along with food and activity tracking tools and a magazine, this plan relies on a support network of local or online meetings. It's a good common-sense plan and studies show it's safe and effective.

•Jenny Craig: Also works on a point system. Relies heavily on pre-packaged meals, which makes it easier to limit portion sizes but increases the cost of the plan.

•Nutrisystem: Similar to Jenny Craig.

•Slim Fast: Limits calories by replacing meals (usually breakfast or lunch) with low-calorie alternatives from the Slim Fast line of packaged foods, which includes shakes, soups, pastas, and snacks. The packaged foods ensure consistent portions and deliver a full day's vitamins and minerals (which can be a shortcoming of other low-calorie diets), and works in combination with sensible eating of regular food.

Most diets fall into one of these categories: Low-calorie or starvation diets, low-fat (high-carb) diets, and low-carb (high-protein) diets. There are many others of course, but we'll focus on these examples.

Low-calorie diets are short-term plans that often restrict total calories to as little as 500 to 1,000 per day. They are used to lose weight in a short amount of time, but they are not good for your health because most simply don't provide enough calories for an adult to function. In fact, they can put your body into starvation mode and lower your metabolism. Extremely low-calorie diets may lead to the development of disordered eating patterns in some people. You shouldn't restrict your calorie intake below your daily recommendation unless you're being closely supervised by a health-care professional.

Examples:

•Cabbage soup diet: Eat as much cabbage soup as you like (plus certain other foods), for one week.

•Grapefruit diet: Eat half a grapefruit before every meal and keep total daily calories under 800 for one to three weeks.

•Juice fasts: Drink only fruit and vegetable juices for a few days.

Low-fat diets work on the idea that most of the extra calories we eat come from extra fat. Each gram of fat has 9 calories, compared with 4 in carbohydrates or proteins. By cutting down on fat, you should be able to reduce enough calories without sacrificing your health. In fact, reducing fat could help your heart: When you reduce fat significantly (from 30 percent of your calories to 10 percent), the proportion of carbohydrates in your diet usually goes up. If you eat this extra carbohydrate in the form of whole grains, the additional fiber may further benefit your health. Examples:

•Dr. Dean Ornish's Life Choice Program (Dr. Dean Ornish)

The idea: This program emphasizes a very low-fat, high-fiber diet coupled with lifestyle changes such as exercise and stress reduction. This is essentially a lacto-ovo vegetarian diet (that is, a diet that includes milk and eggs), and allows for very little meat.

Does it work? The Ornish diet has been proven to halt and reverse heart disease, and to lower insulin, cholesterol, and C-reactive protein. However, many find it too restrictive, and some experts feel that it should include more good fats.

•The Pritikin Calorie Density Solution (Developed in the 1970s by Dr. Nathan Pritikin)

The idea: Similar to the Ornish diet, this is an essentially vegetarian diet that restricts dairy, eggs, and meat, and also advises against eating highly processed plant foods (such as white bread), because processing foods increases calorie density.

Does it work? Like the Ornish diet, most people have problems sticking to a diet that allows such a low amount of fat.

All low-carb diets call for reducing your intake of carbohydrates (including sugars, which are simple carbohydrates) and making up the difference with extra protein (typically 30 to 40 percent of your total calories, or nearly double the usual proportion). They also typically restrict total calories to fewer than 2,000 a day, which may not be enough for active adults. With less ready energy available from carbs, your body is forced to look for other sources of fuel -- fat cells. This breakdown of fat produces a by-product of toxic compounds (ketones) in your blood, a condition called ketosis. When you eliminate these extra ketones in your urine, you also eliminate extra water (which may falsely seem like weight loss), suffer a loss of appetite, and risk dehydration and abnormal heart rhythms. Finally, if you have mild kidney problems already, the extra meat protein can further damage your kidneys. Examples:

•Dr. Atkins New Diet Revolution (the late Dr. Robert C. Atkins)

The idea: The Atkins diet calls for a drastic reduction in carbohydrates while allowing protein and high-fat foods. At first glance, it seems like this diet would be easy to stick to: What's not to like about all the steak, bacon and eggs, and cheeseburgers you can eat? But as the saying goes, if it sounds too good to be true, it probably is.

Does it work? Despite being able to eat all those fatty foods, a year-long study by University of Pennsylvania researchers found that Atkins dieters were just as likely to drop out as dieters on traditional low-calorie diets. And the amount of weight they lost was similar to the amount the low-calorie dieters lost. Add to that the increased risks of heart disease and some types of cancer that come from eating foods high in saturated fats, plus the possible risk of kidney disease for those predisposed to it, and the Atkins diet doesn't seem like much of a bargain.

Researchers are still investigating the long-term effectiveness and risks of the Atkins diet, but you'd be wise to be cautious. Nutrition researchers at Tufts University combed through the Atkins diet book to see if it would be possible to create healthy menus using the book's guidelines. Even after tweaking the food choices a bit, the answer was no. And finally, this: Noted researchers from the Department of Veterans Affairs Medical Center and the University of Minnesota conducted a study of low-carbohydrate diets to see if they can help people with Type 2 diabetes. The only diet they did not test is the Atkins diet. Says lead researcher Dr. Mary C. Gannon, "The Atkins diet promotes ketosis. And we don't want our participants to develop ketosis."

•The South Beach Diet (Dr. Arthur Agatston)

The idea: Another low-carb diet, the South Beach diet began as a way for cardiologist Agatston to help his patients lower their cholesterol, triglycerides, and risk of pre-diabetes. By following his eating plan, they improved these factors and lost weight, too. Agatston's diet differs from the Atkins plan by distinguishing between "good" and "bad" carbohydrates, and allowing moderate consumption of carbs after the first two weeks. It also recommends eating heart-healthy fats and whole grains. The diet defines "good" or complex carbs as those having a lower glycemic index. That is, they take longer to convert to sugar in your bloodstream. "Bad" or simple carbs have a higher glycemic index and cause a spike in blood sugar, leading to hunger and food cravings, according to Agatston. The South Beach diet starts with two weeks of a sharply restricted diet -- the induction period -- followed by a gradual re-introduction of the restricted foods.

Does it work? The South Beach diet claims to cause a sizable weight loss in the first two weeks, but this is most likely from water loss. However, limiting sweet or highly processed foods is a good idea for any diet. There hasn't been any long-term research on the effectiveness or hazards of the South Beach diet, but it has gotten mild endorsements from some nutrition experts. The Center for Science in the Public Interest, for example, has called it a "healthy version of the Atkins diet that's backed by solid evidence on fats and heart disease."

•The Zone Diet (Dr. Barry Sears)

The idea: The Zone diet is based on the premise that food is a drug that affects the level of insulin in your body. Fluctuating insulin levels, according to Sears, affect our mood, endurance, mental acuity, and weight. To keep your insulin at a steady level -- to stay in the Zone -- you must eat meals that consist of 40 percent carbohydrates, 30 percent protein and 30 percent fat. Figuring out what to eat so you fit those requirements is the tricky part. The Zone system breaks the different food groups into "blocks" and "mini-blocks" which are combined to form 5 to 6 small meals a day.

Does it work? The Zone is a milder version of a low-carb, high-protein diet. Each block or mini-block of food consists of a specified serving size, so the result is similar to what you'd get by counting calories on any calorie-restricted diet. Creating a meal plan from different blocks can be a little tedious. There have been no long-term studies on the effectiveness or possible harmful effects of this diet.

•Other low-carb diets

The idea: The Carbohydrate Addict's LifeSpan Program, created by Drs. Richard and Rachael Heller, claims that we become overweight by getting into a "revolving door" of carbohydrate consumption. We eat too many carbs, which, in turn, results in too much insulin in our bodies. This makes us crave even more carbs. To stop this cycle, they recommend substantially reducing carb intake during the day, then eating a "reward" meal in the evening that includes carbohydrates balanced by vegetables and protein. The Protein Power Lifeplan, developed by Drs. Michael and Mary Dan Eades, goes a step further, claiming that the human body doesn't need carbohydrates to function properly (a claim disputed by most nutritionists) and should be fueled by protein instead. Severely limiting your carb intake tricks your body into burning fat for energy, say the Eades. And because you eat high-fat protein, you won't feel hungry.

Do they work? The truth is, most low-carb diets are essentially low-calorie diets with a low-carb/high protein twist. You'll lose weight due to the reduction in calories, but the big drop in pounds that some low-carb diets promise at the start is mostly from water loss. That water loss can also carry away some essential nutrients and leave you dehydrated. Diets that cause ketosis over a long period may also deplete mineral stores in your bones, making them brittle and porous, according to the Mayo Clinic. No long-term, large-scale scientifically validated studies have proven these diets are safe or effective.

To keep your body fit and healthy, you need a strategy that works every day -- for life. Rather than spend money on packaged meals or the latest diet book, it's best to take control of your weight by eating a good mix of vegetables, fruit, grains, and lean protein, and by keeping fat and sugar to a minimum. The American College of Preventive Medicine recommends that you get 55 percent of your calories from carbohydrates, about 25 percent from fat, and the remaining 20 percent from protein. Add regular exercise, and keep in mind your body's changing needs, and you have a recipe for good health.

-- Psyche Pascual and Nina Silberstein contributed to this report.

References

First published March 2, 2004
Last updated December 14, 2007
Copyright © 2004 Consumer Health Interactive

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