RN/DREXEL Home Study Program CE CENTER

CE credit is no longer available for this article. Expired July 2005

Originally posted October 2004

6 diet myths (and the facts that debunk them)

PATRICIA DEPREE, ANP, PhD, CDE

PATRICIA DEPREE is a research coordinator for The Lang Center for Research & Education at New York Hospital Queens in Flushing, NY.

With all of the conflicting information your patients may read about weight loss, it's no wonder they're confused. Here are six common weight-loss myths and the research that disproves them.

If more and more of your patients are asking you how to lose weight, it's probably because they need to. From 1980 to 2000, the prevalence of obesity—defined as having a body mass index >30—among American adults more than doubled, going from 15% to 31%.¹ That number climbs to an estimated 64% when you combine the ranks of those who are obese with those who are overweight (BMI >25 – <30).¹

The common thread that connects overweight and obese individuals is that they consume more calories than they burn.² Although that sounds simple, the cause of this imbalance is typically more complex. While it varies from patient to patient, a combination of genetic, environmental, and psychological factors are often involved.²

And then there are the health risks of obesity, which are well established. Obesity has been linked to an increased risk of Type 2 diabetes, high blood pressure, high cholesterol, heart disease, stroke, sleep apnea, osteoarthritis, and gallbladder and liver disease.^2,3 Men who are obese face an increased risk of dying of cancer of the colon, rectum, and prostate. Similarly, obesity increases a woman's risk of dying of cancer of the breast, uterus, ovaries, or cervix.²

Not surprisingly, most experts agree with the current Dietary Guidelines for Americans (the cornerstone of federal nutrition policy) that suggest that overweight or obese individuals can improve their health by losing weight—especially if they smoke, are sedentary, or have high blood pressure, high cholesterol, or diabetes.³ The problem for many patients, though, may be sorting through the tremendous amount of material written about weight loss to determine what information to believe. And many get little help from their healthcare providers.

In one survey of almost 13,000 obese patients, less than half said a healthcare professional had advised them to lose weight.⁴ Another study found that 22% of consumers are confused by conflicting dietary advice.⁵

When it comes to weight loss, there's no shortage of misinformation. As a nurse, part of your role is to help patients determine which claims are valid and which are not. The following is a look at six widely held diet myths and the research that refutes them.

In recent years, diets that advocate severely restricting the amount of carbohydrates you eat and getting most of your calories from protein and fat have become extremely popular. A typical 2,200-calorie American diet might include 275 gm/day of carbohydrates.⁶ By contrast, the Atkins diet, one of the best-known low-carb diets, limits the intake of carbs to 20 gm/day for the first two weeks, then gradually increases the amount of carbohydrates allowed until the dieter reaches a weight he can maintain. Other popular low-carb diets include the Carbohydrate Addict's Diet, Protein Power, and the South Beach Diet.

Low-carbohydrate diets purportedly work by forcing the body into ketosis—metabolic production of abnormal amounts of ketones. When carbohydrate intake is severely limited, the body turns to stored fat as a source of energy. The loss of stored fat, supporters claim, is what's responsible for the weight reduction.

While those who eat a low-carbohydrate diet do often lose considerable weight quickly, evidence suggests that the weight loss is largely unrelated to restricting carbs. A few studies have found that initially, low-carb diets take off pounds like any other weight-loss diet—by causing a loss of body water.^6,7

Other research suggests that people on low-carb diets who lose weight do so primarily by decreasing the amount of calories they consume.^6,8 One analysis found that a typical low-carb diet is low in calories—1,152 – 1,627 calories/day.⁶ In addition, there is no evidence that the metabolic changes that occur as a result of a low-carb diet are superior to those of other weight-loss diets.⁶

When it comes to the issue of safety and low-carb diets, the news is mixed. One analysis of 94 low-carb diet studies found that a low-carb diet didn't significantly alter lipid, glucose, or insulin levels or blood pressure.⁸

However, in other studies, those on low-carb diets have reported constipation, diarrhea, dizziness, headache, insomnia, nausea, fatigue, and thirst.⁶ One small study found that eating a low-carbohydrate diet for just six weeks increased the acid load delivered to the kidneys, increased the risk of kidney stones, and may have increased the risk of bone loss.⁹ The buildup of ketones can cause the body to produce high levels of uric acid, which is a risk factor for gout and kidney stones.¹⁰

In addition, because these diets are often low in fruits, vegetables, whole grains, and fiber, they can be nutritionally inadequate.⁶ Depending upon which foods are eaten in lieu of carbohydrates, a low-carb diet may provide lower-than-recommended amounts of vitamins A, B₆, and E, folate, calcium, magnesium, iron, potassium, thiamin, and fiber, creating a need for supplements.⁶ Inadequate dietary fiber can cause constipation and might increase the risk of cancer.⁶

Finally, the long-term effects of a low-carb diet are unknown.¹⁰ A recent meta-analysis of the numerous studies of people on low-carb diets located only five studies that had evaluated these diets for longer than 90 days.⁸ The researchers also found limited information on low-carb diets for people older than 50 or those eating no more than 20 gm/day of carbohydrates. They concluded that there was not enough evidence to recommend for or against low-carb diets.⁸

So what should you tell a patient who is about to go on a low-carb diet? Explain that to lose weight, he needs to consume fewer calories than he expends—regardless of which diet he follows.

Tell him that while moderately reducing his carb intake to 100 – 150 gm/day may help him lose weight in the short term, many experts recommend a reduced-calorie, nutritionally balanced weight-loss diet that includes more than 200 gm/day of carbs.⁶ Federal guidelines recommend a diet low in saturated fat and cholesterol and moderate in total fat that's based on the Food Guide Pyramid.³ (See the "A new shape for the pyramid?" box.)

Other moderate-fat, nutritionally balanced diets include that of the American Heart Association, Weight atchers, and DASH.⁶ In addition to dietary advice, these programs typically promote changes in exercise and lifestyle that contribute to overall fitness.

Becoming more active also reduces an overweight or obese patient's risk of dying. One study of almost 10,000 Puerto Rican men found that active overweight or obese men have a significantly lower mortality rate than their sedentary counterparts.¹³ Other research suggests increasing activity results in a similar decline in mortality risk for obese and non-obese individuals alike.¹⁴

Many guidelines recommend that adults participate in 30 minutes of moderate-intensity physical activity five or more days per week.¹⁵ Patients who are sedentary should start slowly and gradually increase the amount and intensity of their activity until they reach the 30-minute goal.¹⁵ But emphasize that there are benefits from any added activity, even for those who don't reach the 30-minute-a-day, five-day-a-week goal or lose a significant amount of weight.

Tell your patients that many of the studies that link yo-yo dieting to an increased risk of certain health problems are at least several years old, while most studies done more recently have found no such connection. For instance, despite earlier studies that found that weight cycling increases blood pressure and cholesterol levels, a 2004 study of some 460 obese men and women found no adverse affect on BP, total or high-density lipoprotein cholesterol, triglycerides, or insulin and insulin resistance.¹⁶

Similarly, a few older studies linked weight cycling to an increased risk of mortality. But a more recent study suggests that the increased risk can often be explained by preexisting disease and smoking.¹⁷

A recent large-scale study of about 47,000 women who'd lost and gained weight at least three times also determined that weight cycling doesn't increase the risk for Type 2 diabetes.¹⁸ And a much smaller study of 195 overweight or obese, sedentary women found that a history of weight cycling has no adverse impact on bone mineral density.¹⁹

It has been suggested, too, that yo-yo dieting makes it harder to lose weight in the future. But most studies show that weight cycling doesn't affect metabolic rate and therefore shouldn't hamper future attempts at weight loss.²⁰

The bottom line: While the risks of weight cycling are debatable, those associated with obesity are clear-cut. Urge obese patients to continue to try to slowly lose a modest amount of weight—10% of body weight over six months or more—to improve their overall health and reduce their risk of obesity-related diseases.²⁰

Many people like to believe that eating a specific kind of food—grapefruit, celery, or cabbage soup, for instance—can speed up weight loss. But that is not the case. While some foods or beverages containing caffeine may temporarily speed up metabolism, they do not cause weight loss.¹⁰ However, foods high in fiber, such as fruits, vegetables, legumes, and whole grains, might help with weight loss by making a person feel full with fewer calories.³

The notion that certain foods should be avoided altogether while trying to lose weight is just as common a belief, and just as flawed. Some of the foods on this list include nuts, dairy products, red meat, and complex carbohydrates such as bread, cereal, rice, and pasta.¹⁰

Tell patients that when eaten in moderation, just about any type of food can be part of a healthy diet. As noted earlier, federal dietary guidelines suggest using the Food Guide Pyramid as a starting point.

For a patient eating a 1,600-calorie-a-day diet, this would include six servings per day from the grains group, three from the vegetable group, two from the fruit group, two or three from the milk group, and two from the meat and beans group.³ Within these guidelines, there's leeway for at least some of the foods often thought of as forbidden, though they recommend that patients trying to lose weight limit the amount of calories they consume from sugar, fats, and oils.

As recent events prove, OTC diet pills can remain on the market for quite some time before their health dangers are fully understood. In February of this year, the Food and Drug Administration banned the sale of dietary supplements that contain ephedrine alkaloids (ephedra, also called Ma huang) after finding that they raise BP and heart rate, which leads to an increased risk of stroke, heart attack, and death.²¹ In fact, the FDA has banned more than 100 ingredients once found in OTC diet products.

There are prescription medications, however, that may be of help; they should be used only by patients at high risk for obesity-related complications such as diabetes or heart disease.²² Most FDA-approved weight-loss medications, including diethylpropion (Tenuate), mazindol (Sanorex, Mazanor), and phentermine (Adipex-P, Fastin, others), are appetite suppressants approved for short-term use of a few weeks or months.²²

Only two drugs—orlistat (Xenical) and sibutramine (Meridia)—are approved for longer-term use.²² Orlistat works by reducing the body's ability to absorb dietary fat by approximately one-third; its side effects include oily or fatty stools, an oily discharge, gas with discharge, and an inability to control bowel movements.

Sibutramine increases the activity of norepinephrine and serotonin to suppress appetite. It may cause small increases in pulse and blood pressure, which may be dangerous for certain patients, such as those with poorly controlled blood pressure or heart disease.²² Both drugs are usually prescribed as part of a weight-loss regimen that includes increased physical activity and a reduced-calorie diet.

Before being prescribed a weight-loss medication, a patient should be thoroughly evaluated to make sure he doesn't have an underlying medical condition, such as hypothyroidism, Cushing's syndrome, or depression, that might be a factor in the weight gain.² A medication history will determine if the patient is or has been taking any medications, such as steroids or certain antidepressants, that might cause weight gain.²

Despite a good deal of evidence to refute it, this myth somehow persists. One study that analyzed seven-day food diaries of 375 men and 492 women found that eating early in the day reduced the total amount consumed throughout the day.²³

Another study showed that subjects who ate cereal or bread for breakfast had a significantly lower BMI than those who skipped breakfast entirely.²⁴ In still another study, researchers analyzing the diets of about 500 subjects found that skipping breakfast was associated with an increased prevalence of obesity.²⁵

Researchers have also examined the role that eating breakfast plays in maintaining weight loss. One study of almost 3,000 patients who'd maintained about a 70-pound weight loss for six years, on average, found that 78% ate breakfast every day; only 4% never ate breakfast.²⁶ This same study found that breakfast eaters were slightly more physically active than non-breakfast eaters.

Clearly, research plays a central role in reshaping the way we care for overweight and obese patients. Also likely to affect our care is a recent change in Medicare policy announced in July by Health and Human Services Secretary Tommy Thompson that opens the door to eventually covering treatments for obesity.

The policy shift received widespread coverage in the mainstream press, and patients who have heard about it are likely to start asking you about weight loss. You won't be able to teach them all they need to know in a single interaction, but clearing up these six myths will be an excellent place to start. RN

REFERENCES

1. National Center for Health Statistics. "Prevalence of overweight and obesity among adults: United States, 1999 – 2000." 2002. www.cdc.gov/nchs/products/pubs/pubd/hestats/obese/obse99.htm (14 July 2004).

2. Weight-control Information Network, National Institute of Diabetes & Digestive & Kidney Disease. "Understanding adult obesity." NIH publication #01-3680. 2001. www.niddk.nih.gov/health/nutrit/pubs/unders.htm (14 July 2004).

3. United States Department of Agriculture and United States Department of Health and Human Services. "Dietary guidelines for Americans, 2000." www.health.gov/dietaryguidelines/dga2000/dietgd.pdf (14 July 2004).

4. Galuska, D. A., Will, J. C., et al. (1999). Are health care professionals advising obese patients to lose weight? JAMA, 282(16), 1576.

5. American Dietetic Association. (2002). Position of the American Dietetic Association: Food and nutrition misinformation. J Am Diet Assoc, 102(2), 260.

6. Freedman, M. R., King, J., & Kennedy, E. (2001). Popular diets: A scientific review. Obes Res, 9(Suppl. 1), 1S.

7. Denke, M. A. (2001). Metabolic effects of high-protein, low-carbohydrate diets. Am J Cardiol, 88(1), 59.

8. Bravata, D. M., Sanders, L., et al. (2003). Efficacy and safety of low-carbohydrate diets: A systematic review. JAMA, 289(14), 1837.

9. Reddy, S. T., Wang, C. Y., et al. (2002). Effect of low-carbohydrate high-protein diets on acid-base balance, stone-forming propensity, and calcium metabolism. Am J Kidney Dis, 40(2), 265.

10. Weight-control Information Network, National Institute of Diabetes & Digestive & Kidney Disease. "Weight-loss and nutrition myths: How much do you really know?" NIH publication #01-4561. 2004. www.niddk.nih.gov/health/nutrit/pubs/myths/index.htm (14 July 2004).

11. American Dietetic Association. (2002). Position of the American Dietetic Association: Weight management. J Am Diet Assoc, 102(8), 1145.

12. President's Council on Physical Fitness & Sports. "Physical activity protects against the health risks of obesity." 2000. www.fitness.gov/digest1200.pdf (14 July 2004).

13. Crespo, C. J., Palmieri, M. R., et al. (2002). The relationship of physical activity and body weight with all-cause mortality: Results from the Puerto Rico Heart Health Program. Ann Epidemiol, 12(8), 543.

14. Haapanen-Niemi, N., Miilunpalo, S., et al. (2000). Body mass index, physical inactivity and low level of physical fitness as determinants of all-cause and cardiovascular disease mortality—16 y follow-up of middle-aged and elderly men and women. Int J Obes Relat Metab Disord, 24(11), 1465.

15. Weight-control Information Network, National Institute of Diabetes & Digestive & Kidney Disease. "Physical activity and weight control." NIH publication #03-4031. 2003. www.niddk.nih.gov/health/nutrit/pubs/physact.htm (14 July 2004).

16. Graci, S., Izzo, G., et al. (2004). Weight cycling and cardiovascular risk factors in obesity. Int J Obes Relat Metab Disord, 28(1), 65.

17. Wannmethee, S. G., Shaper, A. G., & Walker, M. (2002). Weight change, weight fluctuation, and mortality. Arch Intern Med, 162(22), 2575.

18. Field, A. E., Manson, J. E., et al. (2004). Weight cycling and the risk of developing Type 2 diabetes among adult women in the United States. Obes Res, 12(2), 267.

19. Gallagher, K. I., Jakicic, J. M., et al. (2002). Impact of weight-cycling history on bone mineral density in obese women. Obes Res, 10(9), 896.

20. Weight-control Information Network, National Institute of Diabetes & Digestive & Kidney Disease. "Weight cycling." NIH publication #01-3901. 2004. www.niddk.nih.gov/health/nutrit/pubs/wcycling.htm (14 July 2004).

21. U.S. Food and Drug Administration. "Dietary supplements containing ephedrine alkaloids: Final rule summary." 2004. www.fda.gov/oc/initiatives/ephedra/february2004/finalsummary.html (14 July 2004).

22. Weight-control Information Network, National Institute of Diabetes & Digestive & Kidney Disease. "Prescription medications for the treatment of obesity." NIH publication #97-4191. 2003. www.niddk.nih.gov/health/nutrit/pubs/presmeds.htm (14 July 2004).

23. de Castro, J. M. (2004). The time of day of food intake influences overall intake in humans. J Nutr, 134(1), 104.

24. Cho, S., Dietrich, M., et al. (2003). The effect of breakfast type on total daily energy intake and body mass index: Results from the Third National Health and Nutrition Examination Survey (NHANES III). J Am Coll Nutr, 22(4), 296.

25. Ma, Y., Bertone, E. R., et al. (2003). Association between eating patterns and obesity in a free-living US adult population. Am J Epidemiol, 158(1), 85.

26. Wyatt, H. R., Grunwald, O. K., et al. (2002). Long-term weight loss and breakfast in subjects in the National Weight Control Registry. Obes Res, 10(2), 78.

A NEW SHAPE FOR THE PYRAMID?

The U.S. Department of Agriculture (USDA) is currently reassessing its Food Guide Pyramid. This educational tool was introduced in 1992 to help consumers make food choices in keeping with the Dietary Guidelines for Americans, the official federal nutrition recommendations that are updated once every five years. The pyramid translates these recommendations into the kind and amounts of food patients should eat each day.

In light of the increasing prevalence of Americans who are overweight or obese, the USDA maintains, the "one-size-fits-all" guidance outlined by the existing pyramid no longer works. Some people misinterpret the suggested range of six to 11 daily servings from the grains group, for instance, to mean that they can choose from anywhere in that range.

The USDA proposes that the new educational tool—due out early next year—will provide individualized guidance tailored to a person's age, sex, and activity level. As part of the revision, the food guide may no longer be a pyramid. The USDA was soliciting public input on whether to retain the pyramid shape or to go with a new shape for a graphic that better symbolizes the latest nutrition recommendations. A number of nutrition educators, health advocates, and industry groups are in favor of such a change.

Source: U.S. Department of Agriculture, Center for Nutrition Policy and Promotion. "The food guide pyramid update." 2004. www.cnpp.usda.gov/pyramid-update/index.html (14 July 2004).

RESOURCES FOR PATIENTS

American Dietetic Association
120 South Riverside Plaza, Suite 2000
Chicago, IL 60606-6995
(800) 877-1600
www.eatright.org

American Obesity Association
1250 24th Street, NW, Suite 300
Washington, DC 20037
(202) 776-7711
www.obesity.org

Division of Nutrition and Physical Activity
National Center for Chronic Disease Prevention and Health Promotion
4770 Buford Highway, NE, MS/K-24
Atlanta GA 30341-3717
(770) 488-5820
www.cdc.gov/nccdphp/dnpa/

The Weight-Control Information Network
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
1 WIN Way
Bethesda, MD 20892-3665
(202) 828-1025 or (877) 946-4627

 

Helen Lippman, ed. Patricia Depree. Six diet myths (and the facts that debunk them). RN Oct. 1, 2004;67:48.

Published in RN Magazine.