American Journal of Clinical Nutrition, Vol. 81, No. 6, 1298-1306, June 2005

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
Manny Noakes, Jennifer B Keogh, Paul R Foster and Peter M Clifton

Abstract
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.

Design: 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/m2) of 32
+/- 6 and age of 49 +/1 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 ( +/- 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).

Conclusion: 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.

http://www.ajcn.org/cgi/content/abstract/81/6/1298

Tom Billings