Effect of weight loss by a low-fat diet and a low-carbohydrate diet on peptide YY levels

OBJECTIVE: To compare the effects of weight loss by an energy-restricted low-fat diet versus low-carbohydrate diet on serum peptide YY (PYY) levels. DESIGN: 8-week prospective study of 30 obese adults (mean age: 42.8 ± 2.0 years, mean BMI 35.5 ± 0.6 kg/m(2)). RESULTS: After 8 weeks, subjects on the low-carbohydrate diet lost substantially more weight than those on the low-fat diet (5.8 kg vs. 0.99 kg, p<0.001). Weight loss by either diet resulted in a 9% reduction in both mean fasting serum PYY levels (baseline: 103.5 ± 8.8 pg/ml, after weight loss: 94.1 ± 6.5 pg/ml, p<0.01) and postprandial AUC PYY (baseline: (20.5 ± 1.5) × 10(3) pg·hr(−1)ml(−1), after weight loss: mean AUC PYY (18.8 ± 1.4) × 10(3) pg·hr(−1)ml(−1) p<0.001). There was a trend towards lower levels of PYY with greater degrees of weight loss. CONCLUSIONS: Reduced PYY levels after weight loss by an energy-restricted low-fat or low-carbohydrate diet likely represents a compensatory response to maintain energy homeostasis and contributes to difficulty in weight loss during energy-restricted diets.