What does a low-carbohydrate diet do to your LDL cholesterol?
A low-carbohydrate diet raises LDL cholesterol modestly in most people, and sometimes substantially. If you already have elevated LDL or a cardiovascular risk, discuss the diet with your doctor before starting.
LDL cholesterol rises on average slightly on a low-carbohydrate diet compared with a low-fat diet: meta-analyses arrive at an increase of roughly 0.07 to 0.12 mmol/L. A review of seventeen meta-analyses rates that LDL rise as one of the best-supported effects of a ketogenic diet. This is a modest average effect, but individual outliers can be considerably larger.
Particularly striking: in healthy young women of normal weight, LDL cholesterol rose after a ketogenic diet in all seventeen participants, by an average of 1.82 mmol/L. Alongside this, the form of LDL considered most harmful (small and dense) also increased, as did a protein that provides a measurable indicator of cardiovascular risk (apolipoprotein B). The researchers describe this as concerning, precisely because these women had no elevated risk beforehand.
At the same time, the picture is not straightforward. One carefully controlled study with 164 participants following weight loss saw no increase in LDL, even with a high saturated fat content in the diet. And in obese participants, LDL actually fell after 56 weeks. These results differ from the meta-analyses, but the studies are more limited in design or smaller in size, so they do not overturn the overall picture.
For other blood fats the effect is more favourable and consistent: triglycerides fall and 'good' HDL cholesterol rises. Some experts argue that elevated LDL combined with low triglycerides and high HDL is less risky, but this is a contested view without hard outcome data on heart attacks or strokes over the long term.
Whether the LDL rise ultimately leads to more cardiovascular disease in humans has not yet been investigated at scale in long-term trials. This makes it difficult to say whether the risk in practice is smaller or larger than feared. If you already have elevated LDL or a cardiovascular history, it is wise to discuss this with your doctor before following a low-carbohydrate diet for an extended period.
This answer is based on two overviews of multiple randomised trials (one of which summarises seventeen meta-analyses), supplemented by individual randomised studies. The LDL rise attributable to a low-carbohydrate diet is rated by the researchers as high-quality evidence. However, the question of whether that rise also leads to more heart attacks or strokes has not yet been answered by sufficiently large or long-running trials; that part of the evidence base is thin.
How early should you start lowering your LDL cholesterol?
Starting as early as possible pays off: LDL damage accumulates from childhood, and every year that your LDL remains lower counts. If familial high cholesterol runs in your family, discuss with your doctor whether screening from a young age makes sense.
Can losing weight noticeably improve my blood pressure and cholesterol?
Losing weight through a diet noticeably improves blood pressure and cholesterol, especially in the first six months. For those who want to hold on to those gains, the Mediterranean diet is the best-supported choice for the long term.
Are eggs bad for your cholesterol?
Eggs are not automatically bad for your cholesterol; the rest of your diet, especially the amount of saturated fat, carries more weight. If you have high LDL, diabetes or a family history of cardiovascular disease, discuss your egg consumption with your doctor.
What is a healthy HDL (good cholesterol) level, and can I raise it?
Raising HDL through lifestyle is possible, but your genes set the ceiling. Lowering triglycerides through less sugar and alcohol, more exercise, and weight reduction has the greatest effect.
Can your gut microbiome affect your cholesterol?
Your gut microbiome influences your cholesterol through bile acid conversion and the fermentation of fibres. Eating more fibre is the most concrete and safe step to take; supplements such as berberine are not yet sufficiently substantiated for daily use.
Does intermittent fasting lower your cholesterol?
Intermittent fasting probably lowers total cholesterol and LDL modestly, but its effect on 'good' HDL cholesterol is unclear and long-term data are limited. It is a worthwhile strategy as a complement to, not a replacement for, proven treatments.