Targets for LDL-C, ApoB and Small Dense LDL

Mar 17

6 min read

Updated: Oct 3

What Your Cholesterol Results Really Mean, why particle number may matter more than cholesterol mass — and how high visceral fat can mean high risk even when your LDL looks normal.

An article by Dr Edward Leatham, Consultant Cardiologist 1st published March 17 2026 updated Oct 2026 following new ACC Guidelines.

For busy people, or to tune in when on the move, Google Notebook AI audio podcast are available for this story beneath.

Why a Single Cholesterol Number Isn't Enough

Every year, people with raised visceral fat have heart attacks despite having been told their cholesterol is "normal". This is not a failure of medicine. It is sometimes a failure of a single number to capture what is actually circulating in the blood.

Most cholesterol in your blood travels inside protein-coated particles called lipoproteins: VLDL, IDL, LDL, Lp(a) and HDL. All except HDL can contribute to atherosclerosis, the furring of the arteries. A standard blood test measures the mass of cholesterol carried inside these particles — LDL-cholesterol (LDL-C) — which is rather like weighing the cargo of a fleet of lorries without counting how many lorries are on the road. It is the lorries that cause the trouble, and the same cargo can be spread across few or many of them.

ApoB: Counting the Particles That Matter

Apolipoprotein B (ApoB) is a protein present as exactly one molecule on every atherogenic particle — every LDL, VLDL, IDL and Lp(a) in your bloodstream. Measuring ApoB is therefore as close as a routine blood test gets to counting those particles.

For most people LDL-C and the particle count rise and fall together, and LDL-C does its job. The two part company in type 2 diabetes and insulin resistance, in metabolic syndrome, with raised triglycerides, and with high visceral fat — which is common once the waist exceeds half the height. In these states each particle carries less cholesterol, so LDL-C understates how many particles there are. When the two measures disagree, cardiovascular events follow the particle count and not the cholesterol.

Non-HDL-C — total cholesterol minus HDL — captures LDL, VLDL, IDL and Lp(a) and appears on every NHS lipid profile, making it a practical first-line marker. But ApoB is the number to target. This is why some cardiac and cardiometabolic clinics, including ours, measure ApoB and waist-to-height ratio, and in selected patients use low-dose CT to quantify visceral fat.

Small Dense LDL: a Signpost, Not the Mechanism

For three decades small dense LDL has been described as the dangerous kind: nimble enough to slip into the artery wall, sticky enough to be retained, prone to oxidation once trapped. I taught it that way myself. I have changed my mind.

People whose LDL is predominantly small and dense (Pattern B) were found to have roughly three times the risk of heart attack of those with predominantly large, buoyant particles (Pattern A). The association is not in dispute. What it means is. A smaller particle carries less cholesterol, so to move the same amount around the body in smaller containers you need more of them. The question is whether the harm comes from the size or from the number that size implies.

When the two are separated, number wins. Across the UK Biobank, the Women's Health Study and the Framingham Heart Study, ApoB was confirmed as a strong risk factor; once the count was accounted for, smaller particles added no consistent extra risk. A working-group review of 25 clinical studies reached the same conclusion.

The case that breaks the size hypothesis is familial hypercholesterolaemia. It is the most lethal inherited lipid disorder, and untreated it causes coronary disease in early adult life — yet people with FH carry predominantly large LDL particles. What they have is a very great number of them. If large particles were safe, FH would be a benign condition.

Three things do not follow from this. Small dense LDL is not harmless: it is associated with events because it travels with a higher particle count and with the metabolic dysfunction that produced it. Large, "fluffy" LDL is not benign, and anyone reassured on that basis has been given dangerous advice. And LDL-C is not a broken test: for most people it tracks the particle count closely.

What Are You Aiming For?

UK and international guidelines set progressively lower targets as cardiovascular risk rises. The table shows the targets we work to at Surrey Cardiovascular Clinic.

Risk category	LDL-C	Non-HDL-C	ApoB
LowPrimary prevention. Low calculated 10-year risk and no major risk factors.	< 3.0 mmol/L< 116 mg/dL	< 4.0 mmol/L< 155 mg/dL	Not defined—
Borderline / moderateSlightly raised calculated risk; younger people with diabetes and no other risk factors.	< 2.6 mmol/L< 100 mg/dL	< 3.4 mmol/L< 130 mg/dL	< 1.00 g/L< 100 mg/dL
IntermediateCalculated 10-year risk of 5 to under 10%, or a condition that raises risk, such as long-standing diabetes or moderate kidney disease.	< 2.6 mmol/L< 100 mg/dL	< 3.4 mmol/L< 130 mg/dL	< 1.00 g/L< 100 mg/dL
HighCalculated 10-year risk of 10% or more, a significant coronary calcium score, or established cardiovascular disease on the NICE secondary prevention pathway.	< 1.8 mmol/L< 70 mg/dL · NICE secondary: ≤ 2.0 mmol/L	< 2.6 mmol/L< 100 mg/dL	< 0.80 g/L< 80 mg/dL
Very highEstablished cardiovascular disease, severe kidney disease, or familial hypercholesterolaemia with another major risk factor.	< 1.4 mmol/L< 55 mg/dL	< 2.2 mmol/L< 85 mg/dL	< 0.65 g/L< 65 mg/dL
Very-high-risk diseaseRecurrent events despite treatment, or one major event with several high-risk conditions.	< 1.4 mmol/L< 55 mg/dL · < 1.0 mmol/L may be considered	< 2.2 mmol/L< 85 mg/dL	< 0.65 g/L< 65 mg/dL

In people already on a statin, ApoB and non-HDL-C track the remaining risk at least as well as LDL-C does. There is no target for small dense LDL. Nobody has shown that changing particle size, with the count held constant, changes outcomes. The target is the count.

NICE NG238 works in non-HDL-C and LDL-C and sets no ApoB target. The 2019 ESC/EAS guideline gives ApoB targets of below 0.80 g/L at high risk and below 0.65 g/L at very high risk. The 2026 ACC/AHA guideline, published in March 2026, brings back numerical LDL-C goals down to below 1.4 mmol/L in very-high-risk disease, advises measuring Lp(a) once in every adult, and supports measuring ApoB in people on lipid-lowering treatment, particularly with established disease, diabetes or raised triglycerides. The clinical message is consistent: higher risk calls for a lower particle burden.

The VAT Connection

Visceral adipose tissue (VAT) — the fat stored around the abdominal organs — is metabolically active. Central adiposity goes with insulin resistance, and an insulin-resistant liver over-produces VLDL. The downstream signature is familiar: triglycerides up, HDL down, more remnant particles, and LDL particles that are smaller and more numerous. LDL-C stays flat or even falls while ApoB rises. The standard lipid panel therefore understates atherogenic burden in exactly the people whose burden is climbing.

A patient with high visceral fat may have an LDL-C of 2.0 mmol/L, apparently well controlled, and an ApoB of 1.1 g/L. They look treated. On the count, they are not at target.

This is why I regard waist-to-height ratio and ApoB as a pair. A tape measure costs almost nothing. If your waist is more than half your height, ask for an ApoB by name and take the result to your GP. That every adult should know their ApoB, as they know their blood pressure, is my own position — informed by the evidence above, and ahead of routine practice, not a guideline recommendation.

Reducing visceral fat through diet, resistance training and, where clinically indicated, GLP-1-based therapy addresses the metabolic state that generates the excess particles. It belongs alongside lipid-lowering treatment, not in place of it.

VAT Trap