Before I go into what my lipid results were, I thought it would be a interesting to do a literature search to find what data there is in the academic literature looking into the effect of a ketogenic diet on cholesterol.
This is a pretty comprehensive list going back 15 years to 1998. I limited it to papers that either provided enough information in their abstracts and those that I could actually access the entire paper for free. I didn’t want to actually shell out money for papers that required payment since they typically cost around $30 per article!
So in chronological order going back to 1998, here is what I’ve found.
This is an article from 1998 comparing the effects of a high-protein, low carb, low-fat ketogenic diet in treating morbidly obese adolescents (avg wt of 147..8 kg). They found that not only did the subjects lose weight (mean loss of 15.4 kg) but their total serum cholesterol decreased from 162 to 121 mg/dL. They also experienced a decrease in both HDL and LDL. The limitations that I noticed were that they were given a markedly hypocaloric diet (650-725 calories) and their macros broke down to 25 gm carbs, 25 gm fat, and 80-100 gm protein… which doesn’t exactly match up with what I’ve been trying to do with my nutritional ketosis experiment.
This is an article from 2000, authored by Jeff Volek, where they took 10 healthy males and compared their blood markers before and after initiating a ketogenic diet supplemented with 2.5 gm of omega 3 fats. Their macronutrient breakdown matches what I’ve been trying (obviously since it’s by the same author) 65-70% fat, 5-10% carbs, and 20-30% protein. They found that “there were no significant changes in total cholesterol concentrations” with a lot of variation within subjects. In 4 people total cholesterol decreased. They observed an overall transient increase in LDL at week 4 (up to 20.9%) but then came down to baseline. LDL decreased in 4 subjects and increased in 6 subjects. HDL didn’t really change. Triglycerides decreased significantly. The subjects lost on average 4.2 kg.
Here is an article from 2002 where they took 20 normal healthy males and had 12 of them eat a ketogenic diet for 6 weeks (<10% carbs) and compared them to the other 8 who ate their normal diet. One thing that caught my eye was that they said that the B-Hydroxybutyrate (the ketone I’ve been measuring using the blood ketone meter) concentration increased up to 250% for the ketogenic subjects, but when you look at the number, it only went up to 0.40 mmol/L at week 3 and 0.28 mmol/L at week 4. None of them would meet the criteria for ‘nutritional ketosis’ that I’ve been following of having a level between 0.5 – 3.0 mmol/L. Similar to the above study, they found that, “There were significant increases in total and LDL cholesterol that returned to values that were not significantly different than wk 0 values at the end of the ketogenic diet period.” Total cholesterol increased in 7 subjects and decreased in 5 subjects. LDL increased in 7 subjects up to 70% and decreased in 4 subjects. HDL increased in 9 and decreased in 3 subjects. Triglycerides were decreased. All of these markers stayed the same in the 8 subjects who ate their normal diet.
This is an article from 2003 where they looked at the cholesterol levels in 141 children who had difficult-to-control-seizures that were controlled with a ketogenic diet. They observed that at 6 months the total cholesterol (mean 232 mg/dL), LDL (mean 148 mg/dL), VLDL, triglycerides (mean 154 mg/dL), and ApoB proteins ALL increased while HDL decreased by an average of 7 mg/dL. They also found that in the patients they followed up at 12 and 24 months, these changes persisted, though to a lesser degree. A caveat they made sure to mention was that their results, “cannot be directly extrapolated to the use of a ketogenic diet in children or adults for the purposes of weight reduction.”
This article from 2004 compared a low carb diet (< 20 gm) along with supplementation and exercise vs a low fat diet and exercise. They found that the low carb group had better participation, greater weight loss, greater decrease in triglycerides, and greater increases in HDL. The LDL changes were not significant between the two groups, but the low carbers had a slight increase in LDL of 1.6 mg/dL and the low fatters had a slight decrease of 7.4 mg/dL.
Another article from 2004 measured changes in cholesterol levels in 83 obese patients with known high cholesterol and high glucose. They were placed on a ketogenic diet fo 24 weeks (30 gm carbs) and showed, “significant decrease in the level of triglycerides, total cholesterol, LDL cholesterol and glucose, and a significant increase in the level of HDL cholesterol in the patients.”
This article in 2006 measured changes in overweight subjects with high cholesterol and showed that a low carb ketogenic diet along with nutritional supplementation, ” led to beneficial changes in serum lipid subclasses during weight loss. While the ketogenic diet did not lower total LDL cholesterol, it did result in a shift from small, dense LDL to large, buoyant LDL, which could lower cardiovascular disease risk.”
Another article in 2006 showed that there was an overall decrease in body weight, total cholesterol, LDL, triglycerides, and blood glucose with an increase in HDL for obese subjects with either a known history of high cholesterol or normal cholesterol.
Here is an article from 2006 that analyzed 5 other studies (meta-analysis) comparing the effects of low carb diets without caloric restriction vs low fat diets. They found that the people eating low carb lost more weight initially, however after a year there wasn’t much difference. While triglycerides were lower and HDL was higher, they also found that total cholesterol and LDL were increased compared to the low fat group.
Another 2006 article compared biomarkers between subjects who ate a low carb ketogenic diet (60% energy from fat, 5% carbs) vs a low carb non ketogenic diet (30% fat, 5% carbs) over six weeks. Subjects were not allowed to exercise and all of the food was provided in prepackaged meals (sounds delicious!). It’s interesting to see that the B-hydroxybutyrate levels in the ketogenic group only reached a mean of 0.722 mmol/L at the 3rd week and 0.333 mmol/L at week 6. These aren’t very high numbers considering they were only eating 5% total calories from carbs. This might be due to their protein intake accounting for 35% of total energy. While they found that both “diets were equally effective in reducing body weight and insulin resistance” and “reductions in total and LDL-cholesterol concentrations did not differ significantly by group… several participants following the [ketogenic] diet had marked increases in LDL cholesterol.”
Another conclusion they came to, “weekly ratings of perceived hunger did not differ by diet group during the trial, which suggests, as discussed by others (31, 32), that it is the protein content of the diet and not the severity of dietary carbohydrate restriction that affects perceived hunger,” mirrored my own experience.
This article from 2007 showed that in obese patients with type II diabetes who followed a ketogenic diet for 56 weeks experienced significant decreases in weight, blood glucose, total cholesterol, LDL, and triglycerides along with an elevation in HDL levels.
This article from 2008 compared the effects of a ketogenic diet vs a low glycemic calorie restricted diet in obese type II diabetics and found that the HDL went up more and LDL also slightly increased (by a mean of 1.3 mg/dL) in those that followed a ketogenic diet. Those that followed the low glycemic calorie restricted diet actually experienced a slight decrease in LDL, by a mean of 2.8 mg/dL. Here is the table showing these results if you are curious.
This 2010 article recruited obese Norwegian women for 10 weeks and assigned them into two groups, one that ate a normal diet + exercise and one that ate a ketogenic diet + exercise. They used urine test strips to determine whether or not they had reached a ketotic state. In the ketogenic dieters they found a slight increase in LDL by 0.2 mmol/L (they use different units than we do), which they called insignificant, while the normal diet subjects had a slight decrease in LDL by 0.2 mmol/L, which they also called insignificant. HDL didn’t really change in either group. Triglycerides went down s tiny bit for both groups, though slightly more for the ketogenic women.
Their final conclusion was ,”resistance exercise in combination with a ketogenic diet may reduce body fat without significantly changing LBM, while resistance exercise on a regular diet may increase LBM in without significantly affecting fat mass. Fasting blood lipids do not seem to be negatively influenced by the combination of resistance exercise and a low carbohydrate diet.
MY FINAL TAKEAWAY FROM ALL THIS
It seems almost universal that following a ketogenic diet leads to an increase in HDL and a decrease in triglycerides. What happens to total cholesterol and especially LDL is unpredictable since both can either go up, go down, or stay the same with no clear explanation as to why this happens.