Nutricion

Protein, body weight, and cardiovascular health1– 4
Frank B Hu
ABSTRACT Widespread popularity of high-protein diets has drawn controversy as well as scientific interest. By reducing intake of carbohydrates and increasing consumption of fats and proteins, such diets are thought to increase satiety, facilitate weight loss, and improve cardiovascular risk factors. In recent years, many randomizedcontrolled studies have compared the effects of higher-protein diets on weight loss and cardiovascular risk factors with those of lower-protein diets. The aim of this review was to provide an overview of experimental and epidemiologic evidence regarding the role of protein in weight loss and cardiovascular risk. Emerging evidence from clinical trials indicates that higher-protein diets increaseshort-term weight loss and improve blood lipids, but long-term data are lacking. Findings from epidemiologic studies show a significant relationship between increased protein intake and lower risk of hypertension and coronary heart disease. However, different sources of protein appear to have different effects on cardiovascular disease. Although optimal amounts and sources of protein cannot bedetermined at this time, evidence suggests a potential benefit of partially replace refined carbohydrates with protein sources low in saturated fats. Am J Clin Nutr 2005;82(suppl):242S–7S. KEY WORDS High-protein diets, weight loss, cardiovascular risk factors, coronary heart disease, low-carbohydrate diets, blood lipids

and cardiovascular disease. In this review, we provide an overview ofexperimental and epidemiologic evidence on the role of protein in weight loss and risk of cardiovascular disease.
PROTEIN AND BODY WEIGHT

INTRODUCTION

Today, 66% of Americans are overweight, and 33% are considered clinically obese (body mass index 30 kg/m2) (1). The rapid increase in the prevalence of obesity, combined with a lack of effective dietary and pharmacologic treatments, has fueled demandfor alternative dietary approaches, in particular, high-protein diets. In recent years, high-protein diets gained widespread popularity before scientific evidence on their safety or efficacy. Advocates of such diets often recommend protein intakes at or above 25% of total energy, amounts that are substantially higher than the average consumption of protein in the US diet. Proponents of severalpopular diets (especially the Atkins Diet) have long claimed that higher amounts of dietary protein not only facilitate weight loss but also improve cardiovascular risk factors. In recent years, more than a dozen clinical trials have examined the effects of higher-protein diets on weight loss compared with diets lower in protein (2–16). Epidemiologic studies have also assessed the effects of dietaryprotein on blood pressure

Recently, Halton and Hu (17) reviewed 15 randomized controlled studies of a higher-protein diet compared with a lowerprotein diet on weight loss, which lasted for between 7 d and 1 y and used a wide variety of macronutrient ratios and methodologic designs (2–16). Seven of these investigations found a statistically significant decrease in total body weight for thehigher-protein diets (5, 6, 8, 12, 13, 15, 16). Samaha (12) randomized 64 obese patients to receive counseling on maintaining a high-protein, low-carbohydrate diet (22% protein) and 68 to receive counseling on consuming a low-fat, high-carbohydrate diet (16% protein). After 6 mo, the high-protein, low-carbohydrate group lost significantly more weight (5.8 vs 1.9 kg; P 0.002). However, at 12 mo, weightloss was not significantly different between the two groups (18). Skov (13) found that obese subjects randomized to a high-protein intake (25% of energy) lost significantly more weight (8.8 vs 5.1 kg) and fat (7.6 vs 4.3 kg) after 6 mo compared with those on a low protein diet (12% of energy). Brehm (6) conducted a randomized trial on 42 obese females. Twenty received a low-fat dietary regimen...