It is currently not known whether ketogenic diets decrease
or increase the risk of cardiovascular disease (CVD) events, including heart
attacke and stroke.
There are studies looking at biomarkers of CVD risk, and a
new meta-analysis has summarized current evidence (from 27 randomized
controlled trials, including 1278 participants in total):
On average, ketogenic diets …
… increase total cholesterol by ~14 mg/dL (~0.36 mmol/L)
… increase LDL cholesterol by ~14 mg/dL (~0.35 mmol/L)
… increase HDL cholesterol by ~6 mg/dL (~0.16 mmol/L)
[… increase non-HDL-cholesterol ~8 mg/dL (~0.20 mmol/L)]
but
… decrease blood glucose by ~3 mg/dL (~0.18 mmol/L)
… decrease blood insulin by ~8 pmol/L
… decrease diastolic blood pressure by ~1 mmHg
… decrease body weight by ~2.6 kg
… decrease body mass index (BMI) by ~ 1.6 kg/m2
and
… have no effect on HbA1c
… have no effect on HOMA index of insulin resistance
… have no effect on systolic blood pressure
… have no effect on waist circumference
Putting it into context:
The authors note that "numerous and multiple different types of clinical and genetic studies unequivocally has [have] established that high TC [total cholesterol] and LDL cholesterol concentrations were associated with an increased risk of CVD [cardiovascular disease]".They write: "Although HDL cholesterol is often referred to as “good cholesterol,” no studies have revealed that elevated HDL cholesterol concentrations are causally associated with a lower risk of CVD."
And "[...] the decreased TG [triglyceride] concentration in our study may be attributable to the confounder weight loss instead of ketogenic diets." That is, weight loss caused the TG level to fall. And weight loss can obviously be achieved in many ways, not just by following a ketogenic diet.
And: "[...] our findings on diastolic pressure were only based on 7 RCTs, so the results on diastolic pressure should be interpreted with care." And the effect on diastolic blood pressure was very small, with no effect on systolic blood pressure.
The authors conclude:
"Although the ketogenic diet showed advantages in TG and diastolic blood pressure reduction, weight control, and glycemic control, the efficacy of ketogenic diets on CVD risk factors should be treated with caution considering the abnormalities in [i.e., the increasing effect of ketogenic diets on] TC and LDL cholesterol.""Along with very low-carbohydrate proportion in ketogenic diets, fat makes up a high percentage of the diet. Dietary fats are divided into 2 main categories: saturated fats and unsaturated fats. Saturated fat is detrimental to health in the long term [..]. WHO [the World Health Organization] suggested that saturated fat intake should be <10% of total energy [calories consumed] and transfer to unsaturated fat [i.e., unsaturated fat sould be eaten instead] [.]. Previous evidence supported that the reduction of saturated fat was effective on CVD risks [.]. Consequently, taking [i.e., adhering to] ketogenic diets rich in saturated fat is not advisable for reducing CVD risks. Significantly, the present study focused solely on the impact of ketogenic diets on CVD risk factors, rather than the impact on CVD prevention and treatment." [Wang et al. 2024]
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