Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 15616799 · doi:10.1007/s00125-004-1603-4
What was done
Ninety-six normoglycaemic, insulin-resistant overweight women (BMI >27 kg/m²) were randomized to one of three dietary interventions: a high-carbohydrate, high-fibre diet (HC), a high-fat Atkins diet (HF), or a high-protein Zone diet (HP). Advice focused on food choices without total energy prescriptions to mimic clinical practice. The study consisted of an 8-week supervised weight loss phase, an 8-week supervised weight maintenance phase, and a final 8-week phase with no researcher contact. Body composition and cardiovascular/diabetes risk markers were assessed.
What was found
Body weight, waist circumference, triglycerides, and insulin levels decreased across all three diets. Compared with the HC diet, the HF and HP diets produced significantly greater reductions (p<0.01) in weight loss (HF -2.8 kg, HP -2.7 kg), waist circumference (HF -3.5 cm, HP -2.7 cm), and triglycerides (HF -0.30 mmol/l, HP -0.22 mmol/l). Reductions in insulin did not differ significantly between groups. LDL cholesterol decreased in HC and HP groups but fluctuated in the HF group, resulting in significantly lower LDL in the HP group versus the HF group (-0.28 mmol/l, 95% CI 0.04-0.52, p=0.02). A >10% increase in LDL cholesterol occurred in 25% of participants on the HF diet, compared with 13% on HC and 3% on HP.
Why it matters
In clinical practice, a reduced-carbohydrate, high-protein diet appears to offer greater metabolic and weight loss benefits than standard high-carbohydrate advice, while avoiding the adverse LDL cholesterol increases frequently seen with high-fat diets.
Limits
The trial included only normoglycaemic, insulin-resistant women, so findings cannot be generalized to men or individuals with type 2 diabetes. The study relied on dietary counseling rather than provided meals, had an unsupervised final phase, and evaluated short-term intermediate markers rather than long-term clinical cardiovascular endpoints.
Cited by
- context A fasting triglyceride level over 100 mg/dL (or over 1.1 mmol/L) indicates excess dietary carbohydrate consumption relative to one's metabolic capacity.