Dietary Protein and Weight ReductionA Statement for Healthcare Professionals From the Nutrition Committeeof the Council on Nutrition, Physical Activity, and Metabolismof the American Heart AssociationSachiko T. St. Jeor, RD, PhD; Barbara V. Howard, PhD; T. Elaine Prewitt, RD, DrPH;Vicki Bovee, RD, MS; Terry Bazzarre, PhD; Robert H. Eckel, MD;for the AHA Nutrition CommitteeAbstract—High-protein diets have recently been proposed as a “new” strategy for successful weight loss. However,variations of these diets have been popular since the 1960s. High-protein diets typically offer wide latitude in proteinfood choices, are restrictive in other food choices (mainly carbohydrates), and provide structured eating plans. They alsooften promote misconceptions about carbohydrates, insulin resistance, ketosis, and fat burning as mechanisms of actionfor weight loss. Although these diets may not be harmful for most healthy people for a short period of time, there areno long-term scientific studies to support their overall efficacy and safety. These diets are generally associated withhigher intakes of total fat, saturated fat, and cholesterol because the protein is provided mainly by animal sources. Inhigh-protein diets, weight loss is initially high due to fluid loss related to reduced carbohydrate intake, overall caloricrestriction, and ketosis-induced appetite suppression. Beneficial effects on blood lipids and insulin resistance are due tothe weight loss, not to the change in caloric composition. Promoters of high-protein diets promise successful results byencouraging high-protein food choices that are usually restricted in other diets, thus providing initial palatability, anattractive alternative to other weight-reduction diets that have not worked for a variety of reasons for most individuals.High-protein diets are not recommended because they restrict healthful foods that provide essential nutrients and do notprovide the variety of foods needed to adequately meet nutritional needs. Individuals who follow these diets aretherefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liverabnormalities overall. (Circulation. 2001;104:1869-1874.)Key Words: AHA Science Advisory䡲diet䡲nutrition䡲protein䡲obesityBecause more than half of all adults in the United Statesare either overweight or obese1–3and because theseconditions are associated with increased risk of heart disease,overall morbidity, diabetes, hypertension, dyslipidemia,stroke, gallbladder disease, osteoarthritis, sleep apnea, andrespiratory problems, as well as some forms of cancer,effective weight reduction and maintenance strategies areneeded.4Americans are concerned about what they areeating, as demonstrated by an overall decline in the propor-tion of total fat intake to ⬇34% of kilocalories per day.However, there has been an apparent concomitant increase intotal energy intake in the average US adult,4and significantweight gains have been observed over time. It is evident thatweight-reduction efforts have met with limited success andthat the treatment of obesity is complex and difficult. Impor-tantly, most American adults are dieting.5Thus, the popular-ity of diet books promoting high-protein intakes with empha-sis on some form of carbohydrate restriction is of concern toinformed health professionals because of the lack of scientificevidence to support their claims and their long-term adverseimplications for overall health.6,7Although consensus exists that caloric restriction pro-motes weight loss, the effect of varying the macronutrientcomposition of the diet on weight loss has been debated.Diets with altered levels of protein, carbohydrate, or fat arefrequently popular with the dieting public, which is des-perate to find new strategies for successful weight loss andmaintenance. Attention continues to be focused on modi-fication of fat and carbohydrate intake, because these arethe major contributors of energy in the diet. However,controversies regarding the efficacy, benefits, and conse-quences of high-carbohydrate and/or low-fat diets inThe American Heart Association makes every effort to avoid any actual or potential conflicts of interest that may arise as a result of an outsiderelationship or a personal, professional, or business interest of a member of the writing panel. Specifically, all members of the writing group are requiredto complete and submit a Disclosure Questionnaire showing all such relationships that might be perceived as real or potential conflicts of interest.This statement was approved by the American Heart Association Science Advisory and Coordinating Committee in June 2001. A single reprint isavailable by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Ave, Dallas, TX75231-4596. Ask for reprint No. 71-0211.© 2001 American Heart Association, Inc.Circulation is available at http://www.circulationaha.org1869AHA Science Advisoryweight-management efforts frequently pique interest inhigh-protein diets as alternative strategies.This advisory provides a brief overview regarding the roleof protein in the diet and reviews the recent popular high-protein diets and summarizes their limitations. This advisoryalso builds on and extends recommendations of the currentAmerican Heart Association Dietary Guidelines8to includeconsiderations regarding high-protein intake specifically forpurposes of weight reduction. New guidelines for evaluatinghigh-protein diets are provided.Role of Protein in the DietProteins are essential components of the body and arerequired for the body’s structure and proper function. Proteinsfunction as enzymes, hormones, and antibodies, as well astransport and structural components. Transamination andoxidation result in elimination of protein as water, carbondioxide, and nitrogen.9,10The continual process of synthesisand subsequent breakdown of protein in the body is referredto as protein turnover. The rate of protein turnover affectsorgan protein mass, body size, and ultimately the body’sprotein and amino acid requirements.10,11Amino acids11are the central units in protein metabolism.They are incorporated into various proteins and converted tometabolically essential compounds (ie, nucleic acids, creat-ine, and porphyrins). Of the ⬇20 amino acids in humanproteins, 12 are manufactured by the body and are known asnonessential amino acids. The remaining 8
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