Low-fat versus low-carbohydrate weight reduction diets: effects on weight loss, insulin resistance, and cardiovascular risk: a randomized control trial.
OBJECTIVE
Low-fat hypocaloric diets reduce insulin resistance and prevent type 2 diabetes in those at risk. Low-carbohydrate, high-fat diets are advocated as an alternative, but reciprocal increases in dietary fat may have detrimental effects on insulin resistance and offset the benefits of weight reduction.


METHODS
We investigated a low-fat (20% fat, 60% carbohydrate) versus a low-carbohydrate (60% fat, 20% carbohydrate) weight reduction diet in 24 overweight/obese subjects ([mean +/- SD] BMI 33.6 +/- 3.7 kg/m(2), aged 39 +/- 10 years) in an 8-week randomized controlled trial. All food was weighed and distributed, and intake was calculated to produce a 500 kcal/day energy deficit. Insulin action was assessed by the euglycemic clamp and insulin secretion by meal tolerance test. Body composition, adipokine levels, and vascular compliance by pulse-wave analysis were also measured.


RESULTS
Significant weight loss occurred in both groups (P < 0.01), with no difference between groups (P = 0.40). Peripheral glucose uptake increased, but there was no difference between groups (P = 0.28), and suppression of endogenous glucose production was also similar between groups. Meal tolerance-related insulin secretion decreased with weight loss with no difference between groups (P = 0.71). The change in overall systemic arterial stiffness was, however, significantly different between diets (P = 0.04); this reflected a significant decrease in augmentation index following the low-fat diet, compared with a nonsignificant increase within the low-carbohydrate group.


CONCLUSIONS
This study demonstrates comparable effects on insulin resistance of low-fat and low-carbohydrate diets independent of macronutrient content. The difference in augmentation index may imply a negative effect of low-carbohydrate diets on vascular risk.
Bradley
Una
U
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Belfast, U.K.
Spence
Michelle
M
Courtney
C Hamish
CH
McKinley
Michelle C
MC
Ennis
Cieran N
CN
McCance
David R
DR
McEneny
Jane
J
Bell
Patrick M
PM
Young
Ian S
IS
Hunter
Steven J
SJ
D000328:Adult; D002318:Cardiovascular Diseases / Q000209:etiology* / Q000517:prevention & control; D050528:Diet, Carbohydrate-Restricted; D018752:Diet, Fat-Restricted; D004038:Diet, Reducing / Q000379:methods*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004041:Dietary Fats / Q000008:administration & dosage*; D002149:Energy Intake; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014655:Vascular Resistance; D015431:Weight Loss
D004040:Dietary Carbohydrates; D004041:Dietary Fats