Low carbohydrate diets are often criticized for being high in fat, particularly saturated fat, which is widely believed to raise cholesterol levels and increase risk for heart disease, despite recent and older studies demonstrating that saturated fat is not to blame. However, many lipidologists believe that LDL particle number (lower number is better) and pattern (larger size is better) do correlate with heart disease risk.
My total, HDL, and LDL cholesterol have always been on the high side, even back in 2007 when I was a pesco-vegetarian who threw out egg yolks rather than eating them. The only time my LDL was in the “optimal” range (less than 100) was the year I ate a vegan diet. However, I was also very hungry and sick a lot that year.
Recently, someone commented on another blog that “Every low-carb Paleo blogger has nightmarish cholesterol levels," or something very similar. That’s a pretty broad generalization and one I don’t agree with. In many (most?) cases, elevated cholesterol levels are due to something other than diet. And are moderately elevated cholesterol levels always bad anyway? From all the research I've seen, it's inflammation that appears to be at the root of heart disease. In addition, low cholesterol levels have been linked to depression, poor memory, and other health issues.
But I was still curious to see what my lipid numbers are like now, 11 months after beginning a very-low-carb, high-
fat diet that includes a fairly high percentage of saturated fat. I decided to order an NMR Lipoprofile test so I could get information about particle numbers, size, and pattern, which I've never had measured before, since I believe this is more important than just looking at LDL and HDL.
LDL Particle Number
LDL-P: 1174 Reference range: Moderate 1000-1299
Borderline High 1300-1599
LDL-C: 124 Reference range: Above optimal 100-129
HDL-C: 97 Reference range >40
Total cholesterol:226 Reference range <200
Triglycerides: 24 Reference range <150
LDL and HDL particles
HDL- P(total): 43.8 Reference range >30.5
Small LDL-P: 103 Reference range <527
LDL size: 21.7 Reference range 20.6-23.0 (Pattern A, Low Cardiovascular Disease Risk)
Insulin resistance score
LP-IR score: 1 Reference range <45
Honestly, these numbers are better than I’d expected. My HDL has always been good, around 65-70, but it’s increased significantly, while my LDL-C has actually gone down a bit. The particle size and numbers are also very good, as are the triglycerides. I guess I shouldn't really be too surprised given research suggesting that a low-carb-high fat diet results in a less atherogenic lipid profile.
My results occurred nearly a year after eating eggs, butter, cream, cheese, and/or coconut oil every single day. Did I also eat a lot of monounsaturated fats in the form of nuts, olives, and avocado on a daily basis and omega-3 fats in fish several times a week? Absolutely -- I eat a lot of all types of fat. But I don’t think the saturated fat has done me any harm; on the contrary, I’ve written before about the benefits of many saturated fats. And limiting my carbs to less than 50 grams a day has resulted in finally normalizing my post-meal blood sugar, which I was unable to do at a moderate low-carb level of 80-100 grams. My weight remains 125 pounds, give or take a pound.
So what do I eat? Here’s yesterday's intake and nutrient analysis courtesy of FitDay.com:
4 oz sardines
3 cups spinach with ½ tsp sea salt cooked in 2 tsp coconut oil
1 cup blackberries with 1 oz sour cream and 1/3 cup chopped pecans
1 sliced red bell pepper with Greek yogurt-guacamole dip (1/2 cup 2% Greek yogurt mixed with 2/3 cup guacamole)
Chia seed cocoa pudding (1 oz chia seed mixed with ½ cup water, 1 Tbsp cocoa powder, ½ tsp sea salt, ½ tsp cinnamon)
Vanilla hazelnut herb tea with 1 tsp half-and-half
Filet Oscar: 6 oz beef filet, 2 oz crab, 2 Tbsp Bearnaise sauce, 1/2 cup each pea pods and summer squash (pictured above)
Fat: 117 grams (62%)
Saturated: 33 grams
Polyunsaturated fatty acids(PUFA): 24 grams
Monounsaturated fatty acids (MUFA): 60 grams
Protein: 97 grams (23%)
Carbohydrates: 68 grams (16%)
Dietary fiber: 33 grams
Effective carbs: 35-51 grams (There are different schools of thought on how to count fiber. If subtracting all fiber from carbohydrate grams, effective carbs are 35 grams; if subtracting half the fiber grams, effective carbs are 51 grams)
This is pretty typical intake for me in terms of macronutrient percentage, fiber, and calories. The majority of my fat intake always comes from MUFA and saturated fat, and most of the PUFAs are the omega-3 fatty acids found in seafood.
So I'm having great results all around on a low-carb, high-fat, whole foods diet. Everyone is different, of course. I'm not arguing that some people have reported increases in LDL cholesterol after switching to a low-carbohydrate diet, although it seems to occur more often in the initial stages, particularly with folks who lose weight rapidly. But the oft-repeated message that a LCHF approach automatically increases cholesterol and risk for heart disease is not borne out by the research, my n=1 results, and those of many others.
Here we go again. A new study appears to link high fat intake to insulin resistance and postmeal blood sugar spikes. All study participants had Type 1 diabetes and were assigned to consume either two low-fat meals and one high-fat dinner or three low-fat meals. Researchers reported that those receiving the high-fat dinner required more insulin (12.6 units vs. 9 units for the low-fat dinner) and that their postprandial blood sugar and insulin levels were higher and stayed high for several hours after eating.
There are a few red flags regarding this study. First of all, the sample size was extremely small (seven people). And this line is revealing:
"The two dinners received by each subject had identical carbohydrate and protein content but they differed in fat content (10 grams vs. 60 grams)."
Now, the amount of carbs each meal contained wasn't reported (or at least I couldn't find it), but the amount of calories was. So by doing some math, we can get a ballpark estimate:
The low-fat dinner contained on average about 600 calories, 10 grams of fat (90 calories), and let's say 25% protein (38 grams, 150 calories), which is probably being generous. That would leave approximately 90 grams (360 calories) of carbohydrate to make the 600 calorie total.
So given the high carbohydrate content of the meal, these results aren't surprising. Fat delays the absorption of carbohydrate and makes accurate dosing of insulin extremely challenging (as CDE Gary Scheiner explains in discussing how to bolus for pizza). Previous studies have demonstrated the deleterious metabolic effects of consuming a high-fat, high-carbohydrate meal, which include insulin resistance, delayed postprandial hyperglycemia, and elevated triglycerides.
However, there is research indicating that a high-fat, low-carbohydrate diet does not produce the same response; in fact, it results in lower insulin needs, less insulin resistance, and better postmeal blood sugar and lipid response in both Type 1 and Type 2 diabetes. And there's enough anecdotal evidence to support these findings many times over.
So this study simply confirms what we already know: The combination of high fat and high carbohydrate is unhealthy. The best chance people with diabetes have of achieving better blood sugar control and decreasing insulin needs is to adopt whatever form of carbohydrate restriction works best for them.
1. Volek JS, et al. Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low-fat diet. Lipids 2009 Apr;44(4):297-309.
2.Volek JS, et al. Effects of dietary carbohydrate restriction vs. low-fat diet on flow-mediated dilation. Metabolism
3. Nielson JV, et al. Low carbohydrate diet int type 1 diabetes, long-term improvement and adherence: a clinical audit. Diabetol Metab Syndr 4: 23, 2012
One of the questions that comes up repeatedly for me -- from colleagues as well as friends -- is whether following a low-carbohydrate, high-fat diet could be detrimental to heart health. A chief concern is that eating foods high in fat, particularly saturated fat, will raise cholesterol levels, thereby increasing the risk of atherosclerotic heart disease. It doesn't really surprise me; after all, for more than 30 year fats have been considered the primary food we should all be cutting back on if we want to avoid coronary artery disease. The USDA's Dietary Guidelines for Americans and My Plate promote whole grains, nonfat milk, fruits, and other foods that are high in carbohydrates and low in fat as a way of decreasing cardiac risk. On the other hand, there is a large body of research showing that lowering carb intake and increasing consumption of fat (both saturated and unsaturated) can result in favorable changes in serum lipids.
Below are a some of the cardioprotective benefits of low-carbohydrate, moderate-protein, high-fat diets:
1. Significant decrease in serum triglycerides. Carbohydrates are a potent stimulator of hepatic triglyceride synthesis and plasma concentration, particularly in the presence of insulin resistance. Lowering carbohydrate intake can reduce triglyceride levels, resulting in lower cardiac risk.
2. Increase in HDL cholesterol. Higher fat intake is positively correlated with improvements in HDL levels, and high HDL cholesterol is considered cardioprotective.
3. Improvement in LDL particle size, glycation, and oxidation. While triglycerides levels almost invariably decline with carbohydrate restriction, LDL cholesterol response appears to be more individualized. LDL has been classified as the "bad" cholesterol for years, and elevated levels are often seen as increasing one's risk of arterial plaque formation and heart disease. However, simply looking at the amount of serum LDL itself gives us very little information about cardiac risk. It is primarily when LDL is oxidized and its particle size small that this lipoprotein becomes most problematic. Restricting carbohydrate intake has been shown to reduce glycation and subsequent oxidation of LDL. A lower-carb, higher-fat diet tends to produce an increase in LDL particle size (known as Pattern A), whereas an abundance of dietary carbohydrate typically results in smaller, denser particles (Pattern B) that increase the likelihood of atherosclerosis.
I also often hear, "If people don't eat whole grains and legumes, how can they consume adequate fiber?" Fiber, particularly the soluble type, has many health benefits. A low-carb diet can easily supply sufficient fiber if it contains plenty of nonstarchy vegetables, nuts and nut butters, seeds, berries, and avocados. Technically a fruit, an average avocado contains about 12 grams of fiber, as well as 16 grams of monounsaturated fat.
As a registered dietitian, I can't endorse a low-carbohydrate diet consisting of 6 eggs fried in butter with 4 slices of bacon for breakfast, 3 hamburger patties for lunch, and a 20-oz steak with a tiny green salad for dinner. While certainly nearly carb-free, it's missing a lot of beneficial phytochemicals found only in plant foods and contains only a couple of grams of fiber. But I firmly believe that a carbohydrate-restricted plan that includes the high-fiber plant foods listed above can be a very heart-healthy way to go.
1. Tay, J., et al. Metabolic effects of weight loss on a very-low-carbohydrate diet compared with an isocaloric high-carbohydrate diet in abdominally obese subjects. J Am Coll Cardiol, 2008. 51:59-6
2. Volek, J.S., et al. Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Prog Lipid Res, 2008, doi: 10.1016/j.plipres.2008.02.0033.
3. Hayek, T, et al. Dietary fat increases high density lipoprotein (HDL) levels both by increasing the transport rates and decreasing the fractional catabolic rates of HDL cholesterol ester and apolipoprotein (Apo) A-I. J Clin Invest, 1993; 91(4);1665-16714.
4. Siri-Tarino, P.W., et al. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr doi: 10.3945/ajcn.2009.27725
Franziska Spritzler, RD, CDE