Popular Diets Versus Dietary Guidelines

An American Cancer Institute Review

Atkins, food combining, Protein Power -- what really works? Furthermore, what kind of diet will help you to not just lose weight, but decrease your risk of cancer and other chronic diseases? Find out more from The American Institute for Cancer Research below.

The American Institute for Cancer Research has evaluated four popular diet books. We wondered if, beneath the promises, any of these books offered advice about nutrition and weight loss that was based on sound science. We analyzed the potential effectiveness and possible health risks associated with each plan.

We discovered that all four share many of the same basic characteristics – characteristics that illustrate the limitations of popular diets in general.

The books reviewed were:

    • Dr. Atkins New Diet Revolution, by Dr. Robert Atkins
    • The New Beverly Hills Diet, by Judy Mazel and Michael Wyatt
    • Protein Power, by Michael Eades, MD and Mary Anne Eades, MD
    • Suzanne Somers' Get Skinny on Fabulous Food, by Suzanne Somers.

Common denominators of the 4 books reviewed

1.   All four plans are essentially low calorie diets

None are advertised as such, however. In fact, each encourages the dieter to eat as much as he or she wants of a particular food. Nevertheless, these diets prescribe a daily caloric intake that is well below average requirements.

2.   Omitting foods can lead to nutrient deficiencies

By omitting certain foods, and sometimes even entire food groups, these diets are deficient in such major nutrients as dietary fiber and carbohydrates, as well as in selected vitamins, minerals, and protective phytochemicals. Dr. Atkins, for one, recommends supplementing the diet with nutritional supplements – and helpfully offers his own line of products.

3.   The diets lack a balance of protein, carbs, and fats

The diets are also out of balance, prescribing a daily dietary intake that is high in protein and fat, low in carbohydrates. These proportions are a far cry from those recommended by AICR and other major health organizations like the American Heart Association and the American Dietetic Association, as well as the Surgeon General and the United States Department of Agriculture.

4.   The diets promote the loss of water weight

On a practical level, such high-protein, high-fat, low-carbohydrate diets tend to promote the loss of water weight. However much this diuretic effect may engender a false sense of accomplishment in the dieter, this weight can and does return quickly.

5.   Imbalanced diets can lead to ketosis

If such an imbalanced diet is maintained, the body soon reverts to a fasting state called ketosis, in which the body begins to metabolize muscle tissue instead of fat. Authors of these diets actually advocate "taking advantage" of ketosis to hasten weight loss. In fact, this state is one of the body's last-ditch emergency responses; deliberately inducing ketosis can lead to muscle breakdown, nausea, dehydration, headaches, light-headedness, irritability, bad breath, and kidney problems. In pregnancy, ketosis may cause fetal abnormality or death. It can be fatal in individuals with diabetes.

6.   The diets can lead to significant health risks

Over an extended period of time, all four diets can give rise to other health risks, as well. By restricting carbohydrates, all four diets inevitably lead to a lack of fiber, which can cause constipation and other gastrointestinal difficulties. In addition, the high amounts of cholesterol and saturated fat they prescribe increase the risk of heart disease and, possibly, some cancers. There is recent evidence that a diet featuring excessive protein may leach calcium from the bones.

7.   Food combining is a baseless idea

The elaborate case they make for eating specific foods in a specific order and at specific times has no nutritional basis, and amounts to a kind of magical thinking.

Below we examine each diet plan in greater depth.

Dr. Atkins' New Diet Revolution

by Dr. Robert C. Atkins, M.D.

This book is simply an update of Dr. Atkins' previous diet, recycled here perhaps to encourage the sale of dietary supplements. Besides the health risks associated with ketosis outlined earlier, there are other long-term concerns associated with this particular plan.

Atkins' diet can lead to the kind of rapid weight fluctuations that adversely effect the heart. Moreover, the breakdown of fatty acids that occurs during ketosis may also increase the risk of heart disease.

One of the basic tenets of Atkins' diet is that sugar causes cancer. Such misleading pronouncements are essentially scare tactics, meant to direct the dieter towards foods on the Atkins plan.

Finally, nothing about this plan encourages the dieter to learn some very basic weight management strategies like portion control and serving sizes, let alone develop the skills necessary for a lifetime of balanced nutrition.

The New Beverly Hills Diet

by Judy Mazel and Michael Wyatt

Ms. Mazel has no health or nutrition credentials. Her "New Beverly Hills Diet" is fundamentally flawed, which curtails any potential long-term effectiveness and even gives rise to certain risks. Specifically, two of Ms. Mazel's theories about digestion are wrong.

The premise of her diet is that enzymes found in food "activate" the human body. Each of the three food groups – proteins, carbohydrates and fats – contain their own set of enzymes to break down food so that the body can properly digest it.

Mazel advocates a practice she terms "Cautious Combining." "It is when you eat and what foods you eat together that matters," she claims. Fruits, for example, contain all of the enzymes necessary to break themselves down into nutrients, and move quickly through the system. Proteins and carbohydrates, however, require special enzymes that slow down the process. Furthermore, enzymes from one food can't "cross over" to work on other food groups.

These suppositions are incorrect. The enzymes necessary for digestion are found within the body, not in the foods we eat.

Mazel also states that fat is just another symptom of indigestion, that when food is not properly digested, it "causes fatness."

In fact, quite the opposite is true – if foods are not properly digested they cannot be absorbed. If they are not absorbed, they cannot be metabolized – into fat or anything else.

On a more practical level, Mazel encourages consuming a single food – grapes for example – for an entire day. This is not only nutritionally inadequate, it is also boring. Thus, it is not a strategy likely to be sustained.

Mazel's plan ends up promoting a wide range of fundamentally unhealthy habits. Of equal concern, however, are the healthy habits it doesn't mention. Mazel, like Atkins, neglects to address portion control and serving sizes, concepts central to any serious program of long-term weight management. Perhaps most puzzling, however, is Mazel's silence on the subject of exercise. Regular physical activity it crucial for losing and maintaining weight, but the closest Mazel gets to this topic is her admonition to chew food thoroughly.

Protein Power

by Michael Eades, M.D. and Mary Dan Eades, M.D.

Of the four diets reviewed, Protein Power gets the most credit for providing sound starting points for weight loss. The authors advise getting a physical exam, setting realistic baselines involving body fat percentages and ideal body weight, relying on internal perceptions rather than the bathroom scale, keeping a food diary, and drinking lots of water. The diet itself, however, places the individual at risk for many of the same problems seen in the other diets examined.

The name of the plan itself, Protein Power, is misleading. The authors recommend 60 grams of protein a day for a relatively active individual with a lean body mass of 100 pounds. But 60 grams of protein is nothing more than the USDA recommended daily allowance for a person of that weight. In fact, the average American normally eats around 100 grams of protein a day. The Protein Power plan simply cuts carbohydrates, producing what is essentially a low-calorie diet.

Which brings us to the plan's directive to consume 25 grams of fiber daily while maintaining a low-carbohydrate intake. This is effectively impossible, as most high fiber foods contain significant amounts of carbohydrates.

The authors blame insulin for a host of ills, including hypertension, heart disease, elevated cholesterol and diabetes. High insulin levels, they say, lead to weight gain and obesity. In fact, the scientific evidence suggests that being obese causes high insulin levels, not the other way around.

Finally, the Eades emphatically state that resistance training (lifting weights) is "better" than aerobic activity. No reliable science suggest one of these two forms of exercise is superior – both are equally important for overall fitness and weight management.

Susanne Somers' Get Skinny on Fabulous Food

by Suzanne Somers

Before she began penning diet books, the only remotely health-related entry on Suzanne Somers' resume was an infomercial for a thigh exerciser. She brings no nutrition credentials to bear on this book, which blames excess fat on the tendency of the body's enzymes to "cancel each other out." Her solution, a Byzantine process of eliminating "Funky Foods" and separating the rest into "Somersized Food Groups" for mixing and matching, has no nutritional basis.

Somers maintains that when proteins and carbohydrates are eaten together, their enzymes "cancel each other out," creating a halt in the digestion process and causing weight gain.

Unfortunately, this reasoning is based on assumptions that are completely false. In fact, the body contains enzymes that are specifically keyed to individual proteins, carbohydrates and fats. These enzymes do not "cancel each other out," because they remain in different areas of the digestive tract.

Furthermore, if digestion did not occur, the resulting lack of protein and carbohydrate absorption would most likely result in weight loss, not the weight gain Somers' predicts. Somers' advice not to drink water with meals because it dilutes the digestive juices and slows digestion is also without merit.

In most other particulars, the Somers's plan closely resembles the three diets AICR reviewed above, and places the dieter at similar risk.

In defending her high-fat plan, Somers states that no reliable long-term studies have shown any negative effects associated with increased fat consumption. This is an untrue assertion. A 1997 AICR report, Food, Nutrition and the Prevention of Cancer: A Global Perspective, identified numerous studies possibly linking a high-fat intake with increased risk of several cancers and other chronic diseases. The report went on to develop a set of general dietary guidelines that protect against disease while promoting overall health.

Why popular fad diets don't work

The notion of the "quick fix" is central to all fad diets. So, too, is the mistaken belief that a change in our bodies can only result from a radical change in how we eat. After all, we look to these diet plans not for help making gradual, long-term adjustments to our overall lifestyle, but to "melt fat in just two weeks!"

That's an important distinction. The word diet originally comes from the Greek diaita, which means "manner of living." Scientists and nutritionists agree that any long-term program of weight loss and maintenance must be more than a matter of rationing carbohydrates and calculating calories. It must extend to the entire "manner of living."

The glycemic index: What it is and what it is not

According to many popular diets, foods that rapidly raise blood sugar levels are responsible for making you fat. Specifically, the four low-carbohydrate, high-protein plans reviewed by AICR attempt to blame overweight and obesity on high insulin levels. They maintain that by avoiding foods that trigger the body to release insulin in great amounts, it is possible to lose fat quickly and permanently.

To make this claim, the fad diet authors ignore the substantial amount of research that runs counter to their "theory." More importantly, however, they have taken a controversial nutritional concept – the Glycemic Index – out of the context for which it was intended. To understand how they have manipulated a scientific idea to bolster their claims, it is important to understand what the Glycemic Index actually is.

The Glycemic Index was first developed in 1981 by scientists led by Dr. David Jenkins at the University of Toronto. In an effort to rethink dietary guidelines for diabetics, which are based on an intricate system of "exchanges," Jenkins and his colleagues charted how quickly various foods affect blood sugar levels. The basic idea of the Glycemic Index has been embraced by many diabetes organizations around the world.

The American Diabetes Association, however, has not yet endorsed glycemic indexing. Its refusal to do so raises questions about its practical importance. Specifically, the ADA believes that the differences in rates of digestion ranked by the Glycemic Index are not sufficient to warrant changes in the diet. The ADA also holds that these individual differences fade even further once different foods are eaten together at meals.

The range of Glycemic Index numbers are derived by comparing the rate of a given food's digestion to that a food known to be rapidly digested. The reference food (different methods use either pure glucose or white bread) is assigned a Glycemic Index of 100, and the tested food is charted against this standard.

Foods with a high Glycemic Index (70 and above) are those that break down quickly and cause a spike in blood sugar levels. Foods with a low Glycemic Index (55 and below) break down more slowly and steadily, providing a sustained supply of energy.

Popular notions regarding the rates of absorption of "simple" and "complex" carbohydrates are refuted by a glance at the Glycemic Index tables. For years, it was thought that sugary foods like candy and ice cream – composed of simple carbohydrates – would be absorbed immediately. Similarly, it was believed that starchier foods like bread and potatoes provided steady, long-term energy. But these assumptions were made solely by studying the chemistry of the foods in question. In the body, they act quite differently: Most sugary foods actually cause very small changes in blood sugar levels, while many starchy foods – white bread and potatoes in particular – cause sharp spikes.

These are some of the important subtleties and contradictions ignored by authors of popular diets. By urging a sweeping ban on all carbohydrates, these books display only a passing familiarity with a nutritional concept whose real-world applications remain to be seen.

Weight loss and the glycemic index: The jury's still out

Ranking the digestion rates of various foods may prove an important reference for diabetics and endurance athletes. Proponents of the Glycemic Index also argue for its potential as a weight-loss tool.

Researchers behind the G.I. believe it is possible – even inevitable – to lose weight and keep it off by consuming a diet composed primarily of foods that rank low on the Glycemic Index. Foods that are slow to be converted into blood sugar, they say, satisfy the appetite without piling on excess calories. In addition, most low-G.I. foods contain only small amounts of fat.

It is this last assertion to which the American Diabetes Association takes particular exception. ADA points out that fats slow digestion, so several foods containing a high fat content, like chocolate and peanuts, end up scoring low on the Glycemic Index. It's possible, they say, that in seeking a diet exclusively defined by the Glycemic Index, an individual may put themselves at higher risk for heart attack and stroke.

At this writing, there is not enough data to gauge its particular effectiveness as a long-term weight-management strategy. Only a few clinical weight-loss trials have yet been performed utilizing the Glycemic Index directly and exclusively. Until many more trials come in, the usefulness of the G.I. as a tool for permanent weight control must remain in question.

It should be noted, however, that the weight-management strategy espoused by researchers who helped develop the G.I. in no way resembles the low-carb, high-protein plan of Popular Diets. Most of the foods with low G.I.s , in fact, are fruits, vegetables, grains and beans, so the diet espoused by Index researchers looks quite different from the meat-, milk- and cheese-based plans found on the bestsellers lists today.

Fad diets and "food combining"

Two of the diet plans reviewed by AICR take this misreading even further and feature the mysterious practice of "proper food combining."

Both Judy Mazel's New Beverly Hills Diet and Suzanne Somers' Get Skinny on Fabulous Food offer sternly worded cautions against certain combinations of foods. Mazel espouses several theories about the mechanics of digestion that are scientifically incorrect. Somers misinterpretation of the digestive process leads her to the assertion that certain digestive enzymes "cancel each other out," which "leads to fatness."

The Glycemic Index itself is nothing more than a means to gauge the relative rates of digestion of certain foods. It does not contain, nor does it suggest, any particular theory regarding the body's enzymatic activity. Neither does it speak to the order in which foods can or should be eaten.

Keeping things in proportion for overall health

All of the major health organizations and agencies agree on one thing: A diet high in vegetables, fruits, grains and beans and low in fat is essential to avoiding chronic disease like cancer, heart disease and stroke.

AICR's Dietary and Health Guidelines call for consuming five or more servings of vegetables and fruit each day and seven or more servings of whole grains, beans and tubers. Eating so many servings of plant-based foods cuts down on foods of animal origin – which the guidelines encourage you to limit.

Following these guidelines leads to healthy proportions on your plate. Vegetables, fruits, beans and whole grains, all good sources of carbohydrates, may take up to two-thirds of the space. Animal sources of protein and fat will be minimal. Instead of cookies, cakes and ice cream – all made with animal fats – fresh fruit in the summer and fresh, frozen or canned fruit in the winter can be a common dessert.

The guidelines also call for daily physical exercise to become part of the "manner of living." Regular physical activity is as much a part of overall health and disease resistance as a healthy, nutritious diet.

Most people who make the change from a typical high-fat, sedentary American lifestyle to one which follows these guidelines will slowly, safely lose weight. For those already following these or similar guidelines who feel the need to shed some pounds, the method is simple: Maintain the same nutrient proportions on you plate, slightly decrease portion size, and slightly increase exercise.

Portion control and serving sizes

Portion size is a concept that most Popular Diets do not address. Many call for the elimination of whole categories of macronutrients but ignore this basic nutritional concept. In fact, to lose weight without jeopardizing health, most people should maintain the standard proportion of macronutrients (more carbohydrates from plant-based foods, less protein and fat from animal-based foods.) At the same time, they should increase daily exercise levels and decrease portion sizes.

In general, all Americans need to be aware of portion size, even those not expressly looking to lose weight. Researchers say that Americans routinely underestimate how many calories they consume each day by as much as 25%. Busy lifestyles mean countless distractions, and we're turning into a nation that eats on the run, at our desks, or in front of the television. Individual portions are difficult to gauge when our attention is divided between a large carton of take-out Chinese and the six o'clock news.

At the same time, fast-food chains compete for our business by inflating their serving sizes. Modestly sized bagels and muffins have all but disappeared from American cafes, replaced creations three or four times larger. Restaurants are not far behind, using larger plates laden with more food to assure customers they're getting their money's worth.

Of course, these trends are merely symptoms; how much food we do or do not eat is ultimately up to us. We've simply forgotten when to say when, and so lost sight of a fundamental concept of everyday nutrition: the serving size.

It's on the label of every food package in your house. It's the basic unit of measure used by dietitians and health organizations across the U.S. It lies at the center of every discussion of balanced diets and weight management, but few of us have a clear idea how much food a "serving size" actually represents.

Serving size--What it means

The American Institute for Cancer Research recommends eating five or more servings of fruits and vegetables each day, as well as more than seven servings of grains, legumes, and tubers.

To put serving sizes in perspective, look over the list of examples below. Serving sizes are much smaller than most Americans realize.

According the USDA, 1 serving equals:

  • 1 slice of whole-grain bread
  • 1/2 cup of cooked rice or pasta
  • 3-4 small crackers
  • 1 small pancake or waffle
  • 2 medium-sized cookies
  • 1/2 cup cooked or raw vegetables
  • 1 cup (4 leaves) lettuce
  • 1 small baked potato
  • 3/4 cup vegetable juice
  • 1 medium apple
  • 1/2 grapefruit or mango
  • 1/2 cup berries
  • 1 cup yogurt or milk
  • 1 1/2 ounces of cheddar cheese
  • 1 chicken breast
  • 1 medium pork chop
  • 1/4 pound hamburger patty

The USDA list, helpful as it is, is only one way to get a handle on portions. In 1993 the Food and Drug Administration redesigned food labels to make it easier to gauge serving sizes – and thus calories, fat, protein and nutrients. In addition, they ordered that serving sizes must be clearly stated and consistent for all foods in a given product line. The redesigned "Nutrition Facts" labels appear on most every packaged food product made in the United States.

There is a small but important difference between the serving sizes determined by the USDA and those that appear on food labels. The USDA serving sizes are units of measure that can be used to help balance the overall diet. Those on "Nutrition Facts" food labels are intended to convey information about the specific packaged food in question. Fat, cholesterol, sodium, carbohydrate, protein, vitamins and minerals are calculated for a "typical portion," but keep in mind that the amount of that portion is not a recommendation, it is, once again, merely a unit of measure.

FDA regulations leave the food makers a little wiggle room here, and consumers need to stay alert. Next time you're in the supermarket, compare the serving sizes on the labels of a regular ice cream and a low-fat ice cream. You'll likely discover that the serving sizes for low-fat items are slightly smaller.

Lists and food labels are excellent sources of information for proper portion control, but the most important way to manage how much you're taking in is to develop an eye for serving sizes. Gaining the knack is easier than it sounds; it doesn't mean breaking out the measuring cups and spoons every time you prepare a meal or dine out. AICR recommends two quick ways to become conversant with this important nutritional concept.

Rules of thumb for serving sizes (portions)

The key is to translate the abstract information represented by the serving size into something visual that's easily remembered. So instead of trying to memorize lists of ounce, cup and tablespoon equivalents, simply relate the serving sizes of various foods to familiar physical objects. Here are some tried-and-true "rules of thumb."

Raw vegetables Fist
Cooked vegetables Palm of Hand
Pasta 1 Scoop of Ice Cream
Meat Deck of Cards
Grilled Fish Checkbook
2 Tbs. Butter, Margarine, Peanut Butter, Cream Cheese Thumb (joint to tip)
Snacks (Pretzels, Chips) Handful
Chopped Fruit Tennis Ball
Apple Baseball
Potato Computer Mouse
Bagel (1/2) Hockey Puck
Pancake Compact Disc
Steamed Rice Cupcake Wrapper
Cheese 1 Pair of Dice

The "eyeball" method of serving sizes (portions)

The single best way to determine the amount of food in a given serving, however, is to consult the Nutrition Facts label and measure it out. Of course, measuring every food at each meal is not a particularly practical or enjoyable option, so AICR recommends taking a day to "eyeball" your servings, once and for all.

Check the label, and fill a measuring cup with the appropriately sized portion of vegetables, or chicken, or rice, or snacks. Now empty it onto a plate, and take a good look. How much of the plate is covered? What, exactly, does one serving of pasta look like? Meat? Sauce?

Even if you do this only once, in those few seconds you'll arm yourself with information vital to achieving your weight-management goals. By refocusing attention on an often-overlooked variable in the dieting equation, this method provides a simple and effective reference point. If you've been eating more than you realize, the calories and fat grams steadily add up; sooner or later, the pounds follow. Even if you're not trying to lose weight, taking a moment to see how many servings of cereal you actually eat each morning could help you structure your daily intake.

Easier to control your weight now that you know what a serving size is

Once you develop a sense for servings, you'll find controlling your weight and balancing your diet become easier. You might still load up on your favorite foods once in a while, but you'll be fully aware that you are doing so, and that's the key. Paying attention to portions means eliminating the kind of "unconscious" eating that has helped lead to America's current weight crisis.

Here are some ways to put your newly developed powers of portion control into effect.

At home:

  • Use smaller dishes at meals.
  • Avoid serving food "family style." Serve up plates with appropriate portions in the kitchen, and don't go back for seconds.
  • Put away any leftovers quickly, in separate, portion-controlled amounts. This makes it harder to sneak extra large helpings later on.
  • Never eat out of the bag or carton.

At restaurants:

  • Ask for half or smaller portions. (Don't worry if it doesn't seem cost-effective – it's worth it.)
  • Eyeball your appropriate portion, set the rest aside, and ask for a doggie bag right away. Servings are so big at many restaurants that you may wind up with lunch for two days.
  • At buffets, do a little reconnaissance. Walk the length of the buffet table from the desserts to the appetizers, to know your options. Select only those foods that truly appeal, and keep the rules of thumb in mind. If, for example, you want to try several different kinds of fish, make sure to keep the amounts small enough so that, together, they still fit inside a checkbook-sized serving.
  • If you have dessert, share. (Remember that many restaurant desserts look better than they taste.)

At the supermarket:

  • Beware "mini-snacks" – tiny crackers, cookies, pretzels. Most people end up eating more than they realize, and the calories add up.
  • Choose foods packaged in individual serving sizes. (Again, the extra money you spend is worth the calories you are likely to save.)
  • If you're the type who eats ice cream out of the carton, pick up ice cream sandwiches or other individual size servings.

Reprinted with permission from The American Institute for Cancer Research.