Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women.
BACKGROUND
Limited evidence suggests that a higher ratio of protein to carbohydrate during weight loss has metabolic advantages.


OBJECTIVE
The objective was to evaluate the effects of a diet with a high ratio of protein to carbohydrate during weight loss on body composition, cardiovascular disease risk, nutritional status, and markers of bone turnover and renal function in overweight women.


METHODS
The subjects were randomly assigned to 1 of 2 isocaloric 5600-kJ dietary interventions for 12 wk according to a parallel design: a high-protein (HP) or a high-carbohydrate (HC) diet.


RESULTS
One hundred women with a mean (+/-SD) body mass index (in kg/m(2)) of 32 +/- 6 and age of 49 +/- 9 y completed the study. Weight loss was 7.3 +/- 0.3 kg with both diets. Subjects with high serum triacylglycerol (>1.5 mmol/L) lost more fat mass with the HP than with the HC diet (x +/- SEM: 6.4 +/- 0.7 and 3.4 +/- 0.7 kg, respectively; P = 0.035) and had a greater decrease in triacylglycerol concentrations with the HP (-0.59 +/- 0.19 mmol/L) than with the HC (-0.03 +/- 0.04 mmol/L) diet (P = 0.023 for diet x triacylglycerol interaction). Triacylglycerol concentrations decreased more with the HP (0.30 +/- 0.10 mmol/L) than with the HC (0.10 +/- 0.06 mmol/L) diet (P = 0.007). Fasting LDL-cholesterol, HDL-cholesterol, glucose, insulin, free fatty acid, and C-reactive protein concentrations decreased with weight loss. Serum vitamin B-12 increased 9% with the HP diet and decreased 13% with the HC diet (P < 0.0001 between diets). Folate and vitamin B-6 increased with both diets; homocysteine did not change significantly. Bone turnover markers increased 8-12% and calcium excretion decreased by 0.8 mmol/d (P < 0.01). Creatinine clearance decreased from 82 +/- 3.3 to 75 +/- 3.0 mL/min (P = 0.002).


CONCLUSIONS
An energy-restricted, high-protein, low-fat diet provides nutritional and metabolic benefits that are equal to and sometimes greater than those observed with a high-carbohydrate diet.
Noakes
Manny
M
CSIRO Health Sciences and Nutrition, Adelaide, Australia. manny.noakes@csiro.au
Keogh
Jennifer B
JB
Foster
Paul R
PR
Clifton
Peter M
PM
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001823:Body Composition / Q000187:drug effects / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D003401:Creatine / Q000652:urine; D003404:Creatinine / Q000652:urine; D004038:Diet, Reducing; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D002149:Energy Intake; D005260:Female; D006801:Humans; D008875:Middle Aged; D009752:Nutritional Status; D009765:Obesity / Q000097:blood / Q000150:complications / Q000178:diet therapy* / Q000378:metabolism; D014280:Triglycerides / Q000097:blood; D015431:Weight Loss / Q000187:drug effects / Q000502:physiology
D015415:Biomarkers; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D014280:Triglycerides; D003404:Creatinine; D003401:Creatine