Measuring the number of small LDL particles is the best index of carbohydrate intake I know of, better than even blood sugar and triglycerides. In other words, increase carbohydrate intake and small LDL particles increase. Decrease carbohydrates and small LDL particles decrease.
Carbohydrates increase small LDL via a multistep process:
First step: Increased fatty acid and apoprotein B production in the liver, which leads to increased VLDL production. (Apoprotein B is the principal protein of VLDL and LDL)
Second step: Greater VLDL availability causes triglyceride-rich VLDL to interact with other particles, namely LDL and HDL, enriching them in triglycerides (via the action of cholesteryl-ester transfer protein, or CETP). Much VLDL is converted to LDL.
Third step: Triglyceride-rich LDL is "remodeled" by enzymes like hepatic lipase, which create small LDL.
Carbohydrates, especially if they contain fructose, also prolong the period of time that triglyceride-rich VLDL particles persist in the blood, allowing more time for VLDL to interact with LDL.
Many people are confused by this. "You mean to tell me that reducing carbohydrates reduces LDL cholesterol?" Yes, absolutely. While the world talks about cutting saturated fats and taking statin drugs, cutting carbohydrates, especially wheat (the most offensive of all), cornstarch, and sugars, is the real key to dropping LDL.
However, the effect will not be fully evident if you just look at the crude conventional calculated (Friedewald) LDL cholesterol. This is because restricting carbohydrates not only reduces small LDL, it also increases LDL particle size. This make the calculated Friedewald go up, or it blunts its decrease. Conventional calculated LDL will therefore either underestimate or even conceal the real LDL-reducing effect.
The reduction in LDL is readily apparent if you look at the superior measures, LDL particle number (by NMR) or apoprotein B. Dramatic reductions will be apparent with a reduction in carbohydrates.
Small LDL therefore serves as a sensitive index of carbohydrate intake, one that responds literally within hours of a change in food choices. Anyone following the crude Friedewald calculated LDL will likely not see this. This includes the thousands of clinical studies that rely on this unreliable measure and come to the conclusion that a low-fat diet reduces LDL cholesterol.