Dieting; Obesity; Weight loss
There are many approaches to dieting and many claims for great success with various fad diets. To date, although many diets achieve effective immediate weight loss, none has emerged as an effective tool for maintaining healthy weight. The only definite recommendation that can be made about any diet plan is to be sure it includes an exercise program, assuming there are no health problems to forbid it.
Calorie restriction has been the cornerstone of obesity treatment. The standard dietary recommendations for losing weight are as follows:
Extreme diets of fewer than 1,100 calories carry health risks. They are also often followed by bingeing or overeating, and a return to obesity. Such diets often do not have enough vitamins and minerals, which must then be taken as supplements. Most of the initial weight loss is in fluids. Later, fat is lost, but so is muscle, which can account for more than 30% of the weight loss. No one should be on very strict diets for longer than 16 weeks, or fast for weight loss. Severe dieting has unpleasant side effects, including fatigue, intolerance to cold, hair loss, gallstone formation, and menstrual irregularities. There have been rare reports of death from heart arrhythmias when liquid formulas did not have sufficient nutrients. Pregnant women who excessively diet during the first trimester put their unborn children at risk for birth defects. Of note, those whose diets include a high intake of fluids and much reduced protein and sodium are at risk for hyponatremia, which can cause fatigue, confusion, dizziness, and in extreme cases, coma and death.
This dietary approach requires counting only grams of fat with the goal of achieving 30% or fewer calories from fat. One gram of fat contains nine calories, while one gram of carbohydrates or protein has only four calories. Fat in your diet converts more readily to fat in the body, compared with carbohydrates or proteins. Simply switching to low-fat or skimmed dairy products may be enough for some people.
There are possible drawbacks to this approach:
Some fat in a diet is essential. It should come from plant oils and fish, however, and not from animal products or hardened oils, such as margarine. Trans fatty acids, found in hardened oils, are actually more of a risk factor for obesity than saturated fats from animal products, although both should be avoided.
Fiber and Complex Carbohydrates. In all cases, complex carbohydrates found in whole grains and vegetables are preferred over those found in starch-heavy foods, such as pastas, white-flour products, and potatoes. Fiber is an important component of many complex carbohydrates. Fiber is found only in plants, particularly vegetables, fruits, whole grains, nuts, and legumes (beans and peas). One exception is chitosan, a dietary fiber made from shellfish skeletons. Fiber cannot be digested but passes through the intestines, drawing water with it, and is eliminated as part of feces content. The following are specific advantages from high-fiber diets (up to 55 grams a day):
Low carbohydrate diets generally restrict the amount of carbohydrates but do not restrict protein sources.
The Atkins diet restricts complex carbohydrates in vegetables and, particularly, fruits that are known to protect against heart disease. The Atkins diet can also cause excessive calcium excretion in the urine, which increases the risk for kidney stones and osteoporosis.
"Low-Carb" diets, such as South Beach, The Zone, and Sugar Busters, rely on a concept called the "glycemic index," or GI, which ranks foods by how fast and how high they cause blood sugar levels to rise. Foods on the lowest end of the index take longer to digest. Slow digestion wards off hunger pains. It also helps stabilize insulin levels. Foods high on the glycemic index include bread, white potatoes, and pasta, while low-glycemic foods include whole grains, fruit, lentils, and soybeans.
There has been debate about whether Atkins and other low-carbohydrate diets can increase the risk for heart disease, as people who follow these diets tend to eat more animal-saturated fat and protein and less fruits and vegetables. In general, these diets appear to lower triglyceride levels and raise HDL ("good") cholesterol levels. Total cholesterol and LDL ("bad") cholesterol levels tend to remain stable or possibly increase somewhat. However, large studies have not found an increased risk for heart disease, at least in the short term. In fact, some studies indicate that these diets may help lower blood pressure.
Low-carbohydrate diets help with weight loss in the short term, possibly better than diets that allow normal amounts of carbohydrates and restrict fats. However, overall, there is not good evidence showing long-term efficacy for these diets. Likewise, long-term safety and other possible health effects are still a concern, especially since these diets restrict healthy foods such as fruit, vegetables, and grains while not restricting saturated fats.
Replacing fats and sugars with substitutes may help many people who have trouble maintaining weight.
Fat Substitutes. Fat substitutes added to commercial foods or used in baking deliver some of the desirable qualities of fat, but they do not add as many calories. They cannot be eaten in unlimited amounts, however, and are considered most useful for helping keep down total calorie count.
Olestra (Olean) passes through the body without leaving behind any calories from fat. Studies suggest that it helps improve cholesterol levels and may help overweight people lose weight. Early reports of cramps and diarrhea after eating food containing olestra have not proven to be significant. Of greater concern is the fact that even small amounts of olestra deplete the body of certain vitamins and nutrients that may help protect against serious diseases, including cancer. The FDA requires that the missing vitamins, but not other nutrients, be added back to olestra products.
Beta-glucan is a soluble fiber found in oats and barley. Products using this substance (Nu-Trim) may reduce cholesterol and have additional health benefits.
A number of other fat-replacers are also available. Although studies to date have not shown any significant adverse health effects, their effect on weight control is uncertain, since many of the products containing them may be high in sugar. People who learn to cook using foods naturally lacking or low in fat eventually lose their taste for high-fat diets, something that may not be true for those using fat substitutes.
Artificial Sweeteners. Many artificial or low-calories sweeteners are available. A 2002 study confirmed that people who consumed artificial sweeteners and reduced their sugar intake weighed less over time than those who took in similar types and amounts of drinks and food containing sugar. It should be noted that using these artificial sweeteners should not give dieters a license to increase their fat intake. Studies indicate that consuming some sugar is not a significant contributor to weight gain, as long as the total amount of calories in the diet is under control. There is some public concern about chemicals used to produce many of these sweeteners, and the side effects seen in studies using rats. Natural low-calories sweeteners are available that may be more acceptable to many people.
Other sugar substitutes being investigated include glycyrrhizin (derived from licorice) and dihycrochalcone (derived from citrus fruits).
Some studies have reported good success with meal replacement beverages (such as Slim-Fast and Sweet Success). They contain major nutrients needed for daily requirements. Each serving typically contains 200 - 250 calories and replaces one meal. (Note: Using them for all meals reduces calories to a severe extent and can be harmful.)
One study reported that most subjects who had undergone a 12-week weight loss program followed by using Ultra Slim Fast supplements as directed for maintenance kept off more than half their weight loss after more than 3 years. A quarter of the subjects were still losing weight.
Some evidence suggests that a diet rich in magnesium could reduce a person's risk of metabolic syndrome, a cluster of problems that include obesity, high blood pressure, and high cholesterol. Metabolic syndrome can lead to diabetes and heart disease. Epidemiological studies have found that the risk for metabolic syndrome decreases in those who consume the highest amounts of magnesium from meals.
Bessesen DH. Update on obesity. J Clin Endocrinol Metab. 2008;93(6):2027-2034.
Butryn ML, Phelan S, Hill JO, et al. Consistent self-monitoring of weight: a key component of successful weight loss maintenance. Obesity(Silver Spring). 2007;15(12):3091-3096.
Chu SY, Kim, Lau J, et al. Maternal obesity and risk of stillbirth: a metaanalysis. Am J Obstet Gynecol. 2007;197(3):223-8.
DeMaria EJ. Bariatric surgery for morbid obesity. N Engl J Med. 2007;356(21): 2176-2183.
Despres JP, Golay A, Sjostrom L; Rimonabant in Obesity-Lipids Study Group. Effects of rimonabant on metabolic risk factors in overweight patients with dyslipidemia. N Engl J Med. 2005;353(20):2121-2134.
Dixon JB, O'Brien PE, Playfair J, et al. Adjustable gastric banding and conventional therapy for type 2 diabetes: a randomized controlled trial. JAMA. 299(3):316-323.
Fernstrom JD, Courcoulas AP, Houck PR, et al. Long-term changes in blood pressure in extremely obese patients who have undergone bariatric surgery. Arch Surg. 2006;141(3):276-283.
Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007;297(9): 969-977.
Gorin AA, Phelan S, Wing RR, et al. Promoting long-term weight control: does dieting consistency matter? Int J Obes Relat Metab Disord. 2004;28(2):278-281.
Haworth CM, Plomin R, Carnell S, et al. Childhood Obesity: Genetic and Environmental Overlap with Normal-range BMI. Obesity (Silver Spring). 2008 Apr 17 [Epub ahead of print].
Hsing AW, Sakoda LC, Chua S Jr. Obesity, metabolic syndrome, and prostate cancer. Am J Clin Nutr. 2007;86(3):s843-857.
Hughes AR, Stewart L, Chapple J, et al. Randomized, controlled trial of a best-practice individualized behavioral program for treatment of childhood overweight: Scottish Childhood Overweight Treatment Trial (SCOTT). Pediatrics. 2008;121(3):e539-546.
Koeppen-Schomerus G, Wardle J, Plomin R. A genetic analysis of weight and overweight in 4-year-old twin pairs. Int J Obes Relat Metab Disord. 2001;25(6):838-44.
Kramer MS, Matush L, Vanilovich I, et al. Effects of prolonged and exclusive breastfeeding on child height, weight, adiposity, and blood pressure at age 6.5 y: evidence from a large randomized trial. Am J Clin Nutr. 2007;86(6):1717-1721.
Leslie D. Bariatric surgery primer for the internist: keys to the surgical consultation. Med Clin North Am. 2007; 91(3):353-381, x.
Mustelin L, Silventoinen K, PietilÃinen K, Rissanen A, Kaprio J. Physical activity reduces the influence of genetic effects on BMI and waist circumference: a study in young adult twins. Int J Obes (Lond). 2009;33(1):29-36.
National Center for Health Statistics. Health, United States, 2007 With Chartbook on Trends in the Health of Americans. Hyattsville, MD: 2007.
National Center for Health Statistics. Prevalence of Overweight Among Children and Adolescents: United States, 2003-2004.
Phelan S, Wyatt HR, Hill JO, et al. Are the eating and exercise habits of successful weight losers changing? Obesity (Silver Spring). 2006;14(4):710-716.
Rosenstock J, Hollander P, Gadde KM, et al. A randomized, double-blind, placebo-controlled, multicenter study to assess the efficacy and safety of topiramate controlled release in the treatment of obese type 2 diabetic patients. Diabetes Care. 2007;30(6):1480-1486.
Saunders CL, Chiodini BD, Sham P, et al. Meta-analysis of genome-wide linkage studies in BMI and obesity. Obesity (Silver Spring). 2007;15(9):2263-2275.
Svetke, LP, Stevens VJ, Brantley PJ, et al. Comparison of strategies for sustaining weight loss: the weight loss maintenance randomized controlled trial. JAMA. 2008;299(10):1139-48.
Thompson WG, Cook DA, Clark MM, et al. Treatment of obesity. Mayo Clin Proc. 2007;82(1):93-101.
U.S. Food and Drug Administration. 21 CFR Part 357: Weight Control Drug Products for Overt-he-Counter Human Use; Proposed Rule. Federal Register. Vol. 55, No. 210;October 30, 1990.
Virji A, Murr MM. Caring for patients after bariatric surgery. Am Fam Physician 2006;73:1403-1408.
Wardle J, Carnell S, Haworth CM, et al. Evidence for a strong genetic influence on childhood adiposity despite the force of the obesogenic environment. Am J Clin Nutr. 2008;87(2):398-404.
Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr. 2005;82(1 Suppl):222S-225S.
Woo JG, Dolan LM, Morrow AL, et al. Breastfeeding helps explain racial and socioeconomic status disparities in adolescent adiposity. Pediatrics. 2008;121(3):e458-65.
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