Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: a randomized trial.
Study Goal
The researchers aimed to compare the long-term effects of a low-fat diet versus a low-carbohydrate diet, both combined with comprehensive behavioral treatment, on weight loss and cardiovascular risk factors.
Results Summary
The study found no significant differences in weight loss between the low-fat and low-carbohydrate diets at any time point, with both groups achieving similar weight loss (7% at 2 years). The low-fat diet showed fewer adverse symptoms and lesser improvements in HDL cholesterol compared to the low-carbohydrate diet.
Population
307 participants with a mean age of 45.5 years and a mean BMI of 36.1 kg/m², excluding those with dyslipidemia and diabetes.
Effective Dosage
1200 to 1800 kcal/day, ≤30% calories from fat.
Duration
2 years.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low-carbohydrate diet combined with comprehensive behavioral treatment | decrease | weight | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | approximately 11 kg (11%) at 1 year | resulted in weight loss | #1 |
low-fat diet combined with comprehensive behavioral treatment | decrease | weight | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | approximately 11 kg (11%) at 1 year | resulted in weight loss | #2 |
low-carbohydrate diet combined with comprehensive behavioral treatment | decrease | weight | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | 7 kg (7%) at 2 years | resulted in weight loss | #3 |
low-fat diet combined with comprehensive behavioral treatment | decrease | weight | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | 7 kg (7%) at 2 years | resulted in weight loss | #4 |
low-carbohydrate diet | no change | weight | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had no differences compared to low-fat diet | #5 |
low-carbohydrate diet | no change | body composition | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had no differences compared to low-fat diet | #6 |
low-carbohydrate diet | no change | bone mineral density | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had no differences compared to low-fat diet | #7 |
low-carbohydrate diet | decrease | diastolic blood pressure | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had greater reductions | #8 |
low-carbohydrate diet | decrease | triglyceride levels | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had greater reductions | #9 |
low-carbohydrate diet | decrease | very-low-density lipoprotein cholesterol levels | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had greater reductions | #10 |
low-carbohydrate diet | decrease | low-density lipoprotein cholesterol levels | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had lesser reductions | #11 |
low-carbohydrate diet | increase | symptoms | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | had more adverse symptoms | #12 |
low-carbohydrate diet | increase | high-density lipoprotein cholesterol levels | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | approximating a 23% increase at 2 years | had greater increases | #13 |
low-carbohydrate diet | decrease | cardiovascular disease risk factors | 307 participants with a mean age of 45.5 years and mean body mass index of 36.1 kg/m(2) | - | is associated with favorable changes | #14 |
BACKGROUND: Previous studies comparing low-carbohydrate and low-fat diets have not included a comprehensive behavioral treatment, resulting in suboptimal weight loss. OBJECTIVE: To evaluate the effects of 2-year treatment with a low-carbohydrate or low-fat diet, each of which was combined with a comprehensive lifestyle modification program. DESIGN: Randomized parallel-group trial. (ClinicalTrials.gov registration number: NCT00143936) SETTING: 3 academic medical centers. PATIENTS: 307 participants with a mean age of 45.5 years (SD, 9.7 years) and mean body mass index of 36.1 kg/m(2) (SD, 3.5 kg/m(2)). INTERVENTION: A low-carbohydrate diet, which consisted of limited carbohydrate intake (20 g/d for 3 months) in the form of low-glycemic index vegetables with unrestricted consumption of fat and protein. After 3 months, participants in the low-carbohydrate diet group increased their carbohydrate intake (5 g/d per wk) until a stable and desired weight was achieved. A low-fat diet consisted of limited energy intake (1200 to 1800 kcal/d; <or=30% calories from fat). Both diets were combined with comprehensive behavioral treatment. MEASUREMENTS: Weight at 2 years was the primary outcome. Secondary measures included weight at 3, 6, and 12 months and serum lipid concentrations, blood pressure, urinary ketones, symptoms, bone mineral density, and body composition throughout the study. RESULTS: Weight loss was approximately 11 kg (11%) at 1 year and 7 kg (7%) at 2 years. There were no differences in weight, body composition, or bone mineral density between the groups at any time point. During the first 6 months, the low-carbohydrate diet group had greater reductions in diastolic blood pressure, triglyceride levels, and very-low-density lipoprotein cholesterol levels, lesser reductions in low-density lipoprotein cholesterol levels, and more adverse symptoms than did the low-fat diet group. The low-carbohydrate diet group had greater increases in high-density lipoprotein cholesterol levels at all time points, approximating a 23% increase at 2 years. LIMITATION: Intensive behavioral treatment was provided, patients with dyslipidemia and diabetes were excluded, and attrition at 2 years was high. CONCLUSION: Successful weight loss can be achieved with either a low-fat or low-carbohydrate diet when coupled with behavioral treatment. A low-carbohydrate diet is associated with favorable changes in cardiovascular disease risk factors at 2 years. PRIMARY FUNDING SOURCE: National Institutes of Health.