If you’re concerned about heart health, you might find it difficult to believe that a ketogenic diet—which allows consumption of butter, red meat, bacon, cheese, and other high-fat foods—could be beneficial. After all, for decades we were warned that dietary fat—saturated fat, especially—was a one-way ticket to clogged arteries and heart attacks. Who could forget the infamous March 1984 cover of TIME Magazine that featured bacon and eggs arranged into a frowny face? This scared millions of people away from foods that had been breakfast staples for most of their lives and ushered in an unfortunate era of fearmongering about cholesterol and saturated fat.
But let’s remember that Dr. Robert Atkins, who popularized low-carb and ketogenic diets in the 1970s, was a cardiologist. He wouldn’t have put his patients at risk if he thought low-carb diets caused cardiovascular disease (CVD). When we move away from sensationalist headlines and clickbait articles and focus on the science, the waters are a lot less muddy. With this in mind, let’s see what the science really says about heart-healthy diets.
For decades, the idea that saturated fat “clogged the arteries” prevailed. The words “saturated fat” were never written without being prefaced by the phrase “artery-clogging,” so that it fused into a single entity: “arterycloggingsaturatedfat.” However, several large-scale meta-analyses have debunked the idea that coconut oil, lard, butter, tallow, and other sources of saturated fat cause CVD or increase risk for heart attack. One such analysis out of Harvard University concluded, “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.”1 In a separate review, the same researchers wrote, “Overall, despite the conventional wisdom that reduced dietary saturated fat intake is beneficial for cardiovascular health, the evidence for a positive, independent association is lacking.”2
Operating under the (false) notion that dietary fat, and saturated fat in particular, was bad for the heart and arteries, people cut back on fatty foods but instead of replacing fat calories with calories from lean proteins or vegetables, most people ate more refined carbohydrates. Especially those plastered with slick marketing that they were “fat-free,” which distracted from the fact that they were loaded with sugar. Everyone knows the cookies I’m talking about!
This strategy backfired for many, leading to bigger waistlines and worse cardiovascular health. A review in the American Journal of Clinical Nutrition pulled no punches about this: Replacing saturated fat “with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate the atherogenic dyslipidemia associated with insulin resistance and obesity that includes increased triglycerides, small LDL particles, and reduced HDL cholesterol.”2
So, in following what they thought was a “heart-healthy” diet, people unintentionally did the opposite. Abdominal obesity, low HDL, and high triglycerides are part of the diagnostic criteria for metabolic syndrome, so people didn’t only end up with worse heart health; they also made themselves insulin resistant.
It was long believed that high cholesterol, especially high LDL cholesterol, was the cause of heart disease and heart attacks. Scientific understanding has evolved, though, and it’s now known that the ratio of triglycerides to HDL is a much better indicator of cardiovascular status.3,4,5 Ketogenic diets reliably improve this ratio by lowering triglycerides and raising HDL.6 Reducing carbohydrate consumption, especially in people with type 2 diabetes or metabolic syndrome, has been shown to positively affect abnormal blood lipids that can contribute to atherosclerosis.7 Carbohydrate restriction also typically increases the size of LDL particles, shifting them from small and dense (called “pattern B”) to large and fluffy, (called “pattern A”), which is believed to be more favorable for cardiovascular health. As I’ve written before, don’t blame fat for what the carbs did!
Bearing in mind that pattern A LDL particles and a low TG:HDL ratio are protective for heart health, and that metabolic syndrome (a.k.a. insulin resistance syndrome8) is a major driver of cardiovascular disease9, a truly heart-healthy diet is one that helps people maintain blood glucose and insulin within healthy ranges, induces a favorable TG:HDL ratio, and shifts LDL particles toward pattern A. For many people—especially those with type 2 diabetes, obesity, or metabolic syndrome—this means a low-carb or ketogenic diet.
Ketogenic diets are not, by definition, high in saturated fat. For people who simply don’t enjoy the taste of foods that are high in saturated fat, it’s fine to get most fat from foods higher in mono- and polyunsaturated fats, such as seafood, poultry, avocados, nuts and seeds. But there’s no need to restrict saturated fat on a low-carb diet.10 Saturated fat that builds up in the bloodstream actually results from excessive carbohydrate intake, not from saturated fat in the diet.11,12
It only took TIME magazine thirty years to catch up. In a complete turnaround from the frowning bacon and eggs, a cover story in 2014 encouraged readers to eat butter, because scientists had been wrong about fat being “the enemy.” Whatever your taste preferences—beef or Brazil nuts, cheese or chicken—you can safely embrace delicious dietary fat on your ketogenic diet and know that if you keep carbs very low, you’re doing right by your heart.
- Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91(3):535-46.
- Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. Am J Clin Nutr. 2010;91(3):502-9.
- Hadaegh F, Khalili D, Ghasemi A et al. Triglyceride/HDL-cholesterol ratio is an independent predictor for coronary heart disease in a population of Iranian men. Nutr Metab Cardiovasc Dis. 2009 Jul;19(6):401-8.
- Vega GL, Barlow CE, Grundy SM, Leonard D, DeFina LF. Triglyceride-to-high-density-lipoprotein-cholesterol ratio is an index of heart disease mortality and of incidence of type 2 diabetes mellitus in men. J Investig Med. 2014 Feb;62(2):345-9.
- Kiyosue A. Nonfasting TG/HDL-C ratio seems a good predictor of MACE in CAD patients with statin therapy. Could it be a treatment target? Journal of Cardiology 71 (2018) 8–9.
- Bhanpuri NH, Hallberg SJ, Williams PT, et al. Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study. Cardiovasc Diabetol. 2018;17(1):56. Published 2018 May 1.
- Volek JS, Fernandez ML, Feinman RD, Phinney SD. Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Prog Lipid Res. 2008 Sep;47(5):307-18.
- McCracken E, Monaghan M, Sreenivasan S. Pathophysiology of the metabolic syndrome. Clin Dermatol. 2018 Jan – Feb;36(1):14-20.
- Tune JD, Goodwill AG, Sassoon DJ, Mather KJ. Cardiovascular consequences of metabolic syndrome. Transl Res. 2017;183:57-70.
- Volek JS, Forsythe CE. The case for not restricting saturated fat on a low carbohydrate diet. Nutr Metab (Lond). 2005;2:21. Published 2005 Aug 31. doi:10.1186/1743-7075-2-21.
- Volk BM, Kunces LJ, Freidenreich DJ, et al. Effects of step-wise increases in dietary carbohydrate on circulating saturated Fatty acids and palmitoleic Acid in adults with metabolic syndrome. PLoS One. 2014;9(11):e113605. Published 2014 Nov 21.
- Forsythe CE, Phinney SD, Feinman RD, et al. Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet. Lipids. 2010;45(10):947-62.