Variation in plasma TG mainly varies with levels of VLDL1 levels 1. This variation affects how ApoB is secreted – at low TG, ApoB is secreted as IDL or LDL, at high levels of TG it is secreted as VLDL.
High TG should lead to increased VLDL, and increased LDL from delipidation cascades, it should reduce the amount of directly synthesized LDL. LDL that is directly synthesized is larger than that which is a VLDL remnant, therefore reducing TG levels, should lead to an increased in the overall size of LDL.
1Gofman, J. W., O. Delalla, F. Glazier, N. K. Freeman, D. Lindgren, A. V. Nichols, B. Strisower, and A. R. Tramplin. 1954. The serum lipoprotein transport system in health, metabolic disorders, atherosclerosis and coronary artery disease. Plasma. 2: 413–484.