Long-term effects of a high-protein, low-carbohydrate diet on weight control and cardiovascular risk markers in obese hyperinsulinemic subjects.
OBJECTIVE
To compare the long-term compliance and effects of two low-fat diets differing in carbohydrate to protein ratio on body composition and biomarkers of cardiovascular disease risk in obese subjects with hyperinsulinemia.


METHODS
Outpatient, parallel, clinical intervention study of two groups of subjects randomly assigned to either a standard protein (SP; 15% protein, 55% carbohydrate) or high-protein (HP; 30% protein, 40% carbohydrate) diet, during 12 weeks of energy restriction (approximately 6.5 MJ/day) and 4 weeks of energy balance (approximately 8.3 MJ/day). Subsequently, subjects were asked to maintain the same dietary pattern for the succeeding 52 weeks with minimal professional support.


METHODS
A total of 58 obese, nondietetic subjects with hyperinsulinemia (13 males/45 females, mean age 50.2 y, mean body mass index (BMI) 34.0 kg/m2, mean fasting insulin 17.8 mU/l) participated in the study.


METHODS
: Body composition, blood pressure, blood lipids, fasting glucose, insulin, CRP and sICAM-1 were measured at baseline and at weeks 16 and 68. Urinary urea/creatinine ratio was measured at baseline, week 16 and at 3 monthly intervals thereafter.


RESULTS
In total, 43 subjects completed the study with similar dropouts in each group (P=0.76). At week 68, there was net weight loss (SP -2.9+/-3.6%, HP -4.1+/-5.8%; P<0.44) due entirely to fat loss (P<0.001) with no diet effect [corrected]. Both diets significantly increased HDL cholesterol concentrations (P<0.001) and decreased fasting insulin, insulin resistance, sICAM-1 and CRP levels (P<0.05). Protein intake was significantly greater in HP during the initial 16 weeks (P<0.001), but decreased in HP and increased in SP during 52-week follow-up, with no difference between groups at week 68, indicating poor long-term dietary adherence behaviour to both dietary patterns.


CONCLUSIONS
Without active ongoing dietary advice, adherence to dietary intervention is poor. Nonetheless, both dietary patterns achieved net weight loss and improvements in cardiovascular risk factors.
Brinkworth
G D
GD
CSIRO Health Sciences and Nutrition, Adelaide, South Australia, Australia.
Noakes
M
M
Keogh
J B
JB
Luscombe
N D
ND
Wittert
G A
GA
Clifton
P M
PM
D000328:Adult; D000886:Anthropometry; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology / Q000517:prevention & control; D004038:Diet, Reducing / Q000523:psychology; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005260:Female; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood* / Q000150:complications; D018836:Inflammation Mediators / Q000097:blood; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000150:complications / Q000178:diet therapy*; D010349:Patient Compliance; D015431:Weight Loss
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D018836:Inflammation Mediators; D008055:Lipids