Does low-carb raise your cholesterol? Pick your fat and see the saturated fat it adds

Does low-carb raise your cholesterol?

It is one of the first worries people have before cutting carbs, and the honest answer is: on average a little, but it depends heavily on what you eat instead. Cholesterol is a fat-like substance carried in your blood. LDL is the kind health bodies watch most, because high levels over many years are linked to heart disease. HDL is the "other" kind, and triglycerides are the fats that float in your blood after you eat.

What the trials found

One meta-analysis (a study that pools many trials) looked at 12 randomised trials of low-carbohydrate diets. On average, compared with people eating more carbohydrate, the low-carb groups had these changes in their blood tests:

Blood marker	Average change (mmol/L)	Likely range
LDL cholesterol	up 0.11	0.02 to 0.19
HDL cholesterol	up 0.10	0.08 to 0.12
Triglycerides	down 0.15	0.07 to 0.23 lower

So the picture is mixed: triglycerides tended to fall and HDL tended to rise, while LDL tended to rise a little. These are averages. Your own result could be higher, lower or unchanged, and the authors note that long-term effects still need more research.

Why the fat you pick matters

Low-carb does not tell you which fat to eat. Butter, cream, fatty meat and coconut oil are high in saturated fat; olive oil, rapeseed oil, nuts and oily fish are mostly unsaturated. Public health bodies agree on the direction here: eating a lot of saturated fat can raise LDL, and swapping some of it for unsaturated fat helps. The WHO suggests keeping saturated fat to under 10% of your daily energy, and the NHS gives upper limits of about 20 g a day for women and 30 g for men.

A Cochrane review of 15 trials with over 15,000 people found that cutting saturated fat was linked to about 21% fewer combined heart and circulation events, with little or no effect on deaths from any cause. That review is about saturated fat in general, not about low-carb eating, but it is why the fat choice is the part of a low-carb plan worth getting right.

Studies that swap saturated fat for unsaturated fat also find that people's LDL responses vary, so a blood test is the only way to know how you respond.

Try it: how much saturated fat does your cooking fat add?

Pick a fat and how many tablespoons you use in a day (cooking, dressing, on vegetables). This only counts that one fat, so meat, cheese, cream and eggs come on top.

Low-carb can fit a healthy heart, but the fat on your plate decides a lot of how.

How to keep a low-carb plate heart-friendly

• Lean on unsaturated fats. Olive oil, rapeseed oil, nuts, seeds, avocado and oily fish do most of the work without much saturated fat.
• Treat butter, cream, fatty and processed meat as extras, not the base of every meal.
• Don't assume coconut oil is a health food. It is about 84% saturated fat, and reviews find it raises LDL or fails to lower it compared with unsaturated oils.
• Keep the fibre. Vegetables, pulses in the amounts that fit your plan, nuts and seeds help. WHO lists fibre-rich carbohydrate as a good replacement for saturated fat.
• Get a blood test. A cholesterol check a few months after you change how you eat shows how you respond.

When to ask a professional

This guide is general information, not medical advice. Talk to a doctor or dietitian before cutting carbs sharply if you already have high cholesterol or a family history of it, have heart disease, take statins, insulin or other medicines for diabetes or blood pressure, are pregnant or breastfeeding, or have or have had an eating disorder. Never stop a prescribed medicine because of what you read here.

Sources

• Dong et al., 2020, PLoS ONE: effects of low-carbohydrate diets on cardiovascular risk factors (meta-analysis of 12 trials)
• WHO: updated guidelines on fats and carbohydrates (2023)
• NHS: eat less saturated fat
• Cochrane (Hooper et al., 2020): reducing saturated fat for cardiovascular disease, summary
• EUFIC: is coconut oil a healthy choice?
• RISSCI-1 study: variation of LDL cholesterol in response to replacing saturated with unsaturated fat