Lack of suppression of circulating free fatty acids and hypercholesterolemia during weight loss on a high-fat, low-carbohydrate diet.
Study Goal
The researchers aimed to compare the metabolic effects of a low-carbohydrate (high-fat) diet versus a high-carbohydrate (low-fat) diet during active weight loss in obese adults.
Results Summary
Weight loss was similar between diets, but the high-fat diet increased LDL cholesterol and free fatty acids without suppressing fasting insulin, while the high-carbohydrate diet reduced LDL cholesterol. No significant differences were found in triglycerides or remnant lipoprotein cholesterol between diets.
Population
Healthy, obese adults (n = 32; 22 women, 10 men; BMI 35.8 ± 2.9 for high-fat group, 36.7 ± 4.6 for high-carb group).
Effective Dosage
High-fat diet: ≤20 g carbohydrates/day; high-carb diet: 55% of total energy intake from carbohydrates.
Duration
6 weeks
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low-carbohydrate diet (< or =20 g/d) | no change | fasting triglycerides | Healthy, obese adults | no significant change | no diet treatment effect | #1 |
low-carbohydrate diet (< or =20 g/d) | no change | remnant lipoprotein cholesterol | Healthy, obese adults | no significant change | no diet treatment effect | #2 |
low-carbohydrate diet (< or =20 g/d) | decrease | fasting insulin | Healthy, obese adults | - | decreased | #3 |
low-carbohydrate diet (< or =20 g/d) | increase | fasting free fatty acids (FFAs) | Healthy, obese adults | - | increased | #4 |
low-carbohydrate diet (< or =20 g/d) | increase | 24-h free fatty acids (FFAs) | Healthy, obese adults | - | increased | #5 |
low-carbohydrate diet (< or =20 g/d) | decrease | 24-h insulin | Healthy, obese adults | - | decreased | #6 |
calorie-restricted, low-fat diet | decrease | 24-h insulin | Healthy, obese adults | - | decreased | #7 |
calorie-restricted, low-fat diet | decrease | fasting LDL cholesterol | Healthy, obese adults | - | decreased | #8 |
low-carbohydrate diet (< or =20 g/d) | increase | LDL-cholesterol concentrations | Healthy, obese adults | - | increased | #9 |
BACKGROUND: Little is known about the comparative effect of weight-loss diets on metabolic profiles during dieting. OBJECTIVE: The purpose of this study was to compare the effect of a low-carbohydrate diet (< or =20 g/d) with a high-carbohydrate diet (55% of total energy intake) on fasting and hourly metabolic variables during active weight loss. DESIGN: Healthy, obese adults (n = 32; 22 women, 10 men) were randomly assigned to receive either a carbohydrate-restricted diet [High Fat; mean +/- SD body mass index (BMI; in kg/m(2)): 35.8 +/- 2.9] or a calorie-restricted, low-fat diet (High Carb; BMI: 36.7 +/- 4.6) for 6 wk. A 24-h in-patient feeding study was performed at baseline and after 6 wk. Glucose, insulin, free fatty acids (FFAs), and triglycerides were measured hourly during meals, at regimented times. Remnant lipoprotein cholesterol was measured every 4 h. RESULTS: Patients lost a similar amount of weight in both groups (P = 0.57). There was an absence of any diet treatment effect between groups on fasting triglycerides or on remnant lipoprotein cholesterol, which was the main outcome. Fasting insulin decreased (P = 0.03), and both fasting (P = 0.040) and 24-h FFAs (P < 0.0001) increased within the High Fat group. Twenty-four-hour insulin decreased (P < 0.05 for both groups). Fasting LDL cholesterol decreased in the High Carb group only (P = 0.003). In both groups, the differences in fasting and 24-h FFAs at 6 wk were significantly correlated with the change in LDL cholesterol (fasting FFA: r = 0.41, P = 0.02; 24-h FFA: r = 0.52, P = 0.002). CONCLUSIONS: Weight loss was similar between diets, but only the high-fat diet increased LDL-cholesterol concentrations. This effect was related to the lack of suppression of both fasting and 24-h FFAs.