Effects of long-term overfeeding on plasma lipoprotein levels in identical twins

Twelve pairs of male monozygotic (MZ) twins (mean age±S.D.: 21±2 years) were subjected to an overfeeding protocol of 4.2MJ (1000kcal) above their pre-established individual daily energy needs, 6 days a week, over a period of 100 days. Body weight increased significantly (gain of 8.1kg, P<0.001), as did fat mass (5.4kg, P<0.001) after overfeeding. Plasma triacylglycerol (TG) levels significantly increased (P<0.05) without change in plasma cholesterol (CHOL). Plasma very-low-density-lipoprotein (VLDL)–TG, VLDL–Apoprotein (Apo) B, low-density-lipoprotein cholesterol (LDL-C) and LDL–Apo B (P≤0.05) rose, whereas high-density-lipoprotein cholesterol (HDL-C) levels fell (P<0.05) raising the CHOL/HDL-C ratio (20%) (P<0.001). Considerable individual differences occurred in plasma lipoprotein responses to overfeeding. However, these changes were not random; significant within-pair resemblance registered for the response of plasma CHOL, TG, VLDL–TG, VLDL-C, LDL–TG, HDL-C, HDL–Apo A–I, HDL2-C, HDL3-C to overfeeding (0.48≤r i ≤0.85). Furthermore, a high within-pair resemblance was found for changes in ratios of CHOL/HDL-C (r i =0.86, P<0.0001) and HDL2-C/HDL3-C (r i =0.69, P<0.01). These results strongly suggest that the response of plasma lipoproteins to chronic energy surplus has a significant genetic component as does the detrimental effect of chronic caloric affluence on CHD risk.