Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomized controlled trial.
BACKGROUND
Despite the popularity of low-glycemic index (GI) and high-protein diets, to our knowledge no randomized, controlled trials have systematically compared their relative effects on weight loss and cardiovascular risk.


METHODS
A total of 129 overweight or obese young adults (body mass index, > or =25 [calculated as weight in kilograms divided by the square of height in meters]) were assigned to 1 of 4 reduced-fat, high-fiber diets for 12 weeks. Diets 1 and 2 were high carbohydrate (55% of total energy intake), with high and low GIs, respectively; diets 3 and 4 were high protein (25% of total energy intake), with high and low GIs, respectively. The glycemic load was highest in diet 1 and lowest in diet 4. Changes in weight, body composition, and blood chemistry profile were studied.


RESULTS
While all groups lost a similar mean +/- SE percentage of weight (diet 1, -4.2% +/- 0.6%; diet 2, -5.5% +/- 0.5%; diet 3, -6.2% +/- 0.4%; and diet 4, -4.8% +/- 0.7%; P = .09), the proportion of subjects in each group who lost 5% or more of body weight varied significantly by diet (diet 1, 31%; diet 2, 56%; diet 3, 66%; and diet 4, 33%; P = .01). Women on diets 2 and 3 lost approximately 80% more fat mass (-4.5 +/- 0.5 [mean +/- SE] kg and -4.6 +/- 0.5 kg) than those on diet 1 (-2.5 +/- 0.5 kg; P = .007). Mean +/- SE low-density-lipoprotein cholesterol levels declined significantly in the diet 2 group (-6.6 +/- 3.9 mg/dL [-0.17 +/- 0.10 mmol/L]) but increased in the diet 3 group (+10.0 +/- 3.9 mg/dL [+0.26 +/- 0.10 mmol/L]; P = .02). Goals for energy distribution were not achieved exactly: both carbohydrate groups ate less fat, and the diet 2 group ate more fiber.


CONCLUSIONS
Both high-protein and low-GI regimens increase body fat loss, but cardiovascular risk reduction is optimized by a high-carbohydrate, low-GI diet.
McMillan-Price
Joanna
J
Human Nutrition Unit, University of Sydney, Sydney, Australia.
Petocz
Peter
P
Atkinson
Fiona
F
O'neill
Kathleen
K
Samman
Samir
S
Steinbeck
Katherine
K
Caterson
Ian
I
Brand-Miller
Jennie
J
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001823:Body Composition / Q000502:physiology; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D004032:Diet / Q000379:methods*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000097:blood / Q000150:complications / Q000178:diet therapy*; D050177:Overweight; D012307:Risk Factors; D016896:Treatment Outcome; D015431:Weight Loss / Q000502:physiology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004044:Dietary Proteins