Earlier this year, I wrote about the Ornish Diet in order to dispel the myth that it can reverse coronary artery disease (CAD). Now I want to discuss the Ketogenic Diet at length. Before I start, I want to make some general comments about a “diet”. First of all, a “diet” is not the answer for long-term weight loss. If one looks at long term data from “diet” studies, the average person is only able to maintain a 6-8% reduction of their body weight long term as compared to before they started dieting. The answer is to change your eating habits.
Although the Mediterranean way of eating is referred to as a “diet”, it is really a lifestyle change and different way of eating. The Mediterranean diet is based on the traditional cuisines of Greece, Italy and other countries that border the Mediterranean Sea. Plant-based foods, such as whole grains, vegetables, legumes, fruits, nuts, seeds, herbs and spices, are the foundation of the diet. Olive oil is the main source of added fat. Fish, seafood, dairy and poultry are included in moderation. Red meat and sweets are eaten only occasionally. Olive oil is the primary source of added fat in the Mediterranean diet. Olive oil provides monounsaturated fat, which lowers total cholesterol and low-density lipoprotein (or "bad") cholesterol levels. Nuts and seeds also contain monounsaturated fat. Fatty fish, such as mackerel, herring, sardines, albacore tuna and salmon, are rich in omega-3 fatty acids. These polyunsaturated fats help fight inflammation in the body. Omega-3 fatty acids also help decrease triglycerides, reduce blood clotting, and lower the risk of stroke and heart failure.
Now it’s time to discuss the ketogenic diet. Before we get into the specifics, it is important to understand there is not one reputable cardiologist that thinks it is beneficial in any way long term. The bottom line is that it is harmful to your overall cardiovascular health and the risks certainly outweigh the benefits. Although keto has maintained huge popularity, it’s not exactly easy to follow. The term “ketogenic diet” generally refers to a diet that is very low in carbohydrate, modest in protein, and high in fat. This mix of fuels aims to induce ketosis, or the production of ketone bodies that serve as an alternate energy source for neurons and other cell types that cannot directly metabolize fatty acids. And while that can lead to weight loss, your cells cannot function properly in a ketotic state. Ketogenic diets as typically implemented in scientific studies limit dietary carbohydrate to <50 g per day with varying amounts of fat and protein. “Low-carbohydrate diets” refer to carbohydrate intake below the recommended dietary allowance of 130 g/day which may not be low enough to induce ketosis.
The effect on nutrient metabolism is profound. During prolonged fasting, some tissues, such as muscle, can directly metabolize free fatty acids released from adipose stores. However, much of this fatty acid is converted into ketones in the liver, which can fuel otherwise-obligate glucose consumers like neurons, minimizing mobilization of body protein for gluconeogenesis. However, to induce the liver to make ketones in the fed state, carbohydrate intake must be minimized and fat intake increased. Protein utilization is also altered on a ketogenic diet; the body shunts as much protein as possible to gluconeogenesis, while the minimum necessary amount is used for tissue repair.
Extreme carbohydrate restriction can profoundly affect diet quality, typically curtailing or eliminating fruits, vegetables, whole grains, and legumes and increasing consumption of animal products. Very-low-carbohydrate diets may lack vitamins, minerals, fiber, and phytochemicals found in fruits, vegetables, and whole grains. Low-carbohydrate diets are often low in thiamin, folate, vitamin A, vitamin E, vitamin B6, calcium, magnesium, iron, and potassium. In the absence of multivitamin supplements, individuals on low-carbohydrate diets are at risk of frank nutritional deficiencies. Even when consuming only nutrient-dense foods, a “4:1 ketogenic diet” is reported to have multiple micronutrient shortfalls, often lacking in vitamin K, linolenic acid, and water-soluble vitamins excluding vitamin B12.
Ketogenic diets are typically low in fiber needed not only for healthful intestinal function but also for microbial production of beneficial colonic short-chain fatty acids which enhance nutrient absorption, stimulate the release of satiety hormones, improve immune function, and have anti-inflammatory and anti-carcinogenic effects. Inadequate intake of these microbiota-accessible carbohydrates found in plant cell walls also increases gut permeability, as bacteria extract the carbon they need from the mucus membrane that protects the gastrointestinal tract instead of fiber. The relative abundance of certain health-promoting, fiber-consuming bacteria has been found to be reduced in children consuming a ketogenic diet for epilepsy. It has been suggested that supplementation of ketogenic diets with fiber and non-digestible carbohydrates might be advisable, although data to confirm that supplementation could counteract the effects of very-low-carbohydrate diets on the gut microbiota are lacking.
Intake of other protective dietary components may also be insufficient, such as phytochemicals (e.g., flavanones and anthocyanins), which are not typically included in multivitamins and for which specific intake targets have not been established. Low-carbohydrate diets are also high in saturated fat and cholesterol which is the cause of atherosclerotic vascular disease..
Now let’s discuss the ketogenic diet effects on obesity and weight management.
Ketogenic diets can induce weight loss. In a 2020 meta-analysis of 38 studies lasting 6–12 months and including 6,499 participants, low-carbohydrate diets, defined here as <40% of energy from carbohydrate, led to a small weight loss, compared with low-fat diets, defined as <30% of energy from fat.
It has been proposed that weight loss on ketogenic diets may be due to reduced appetite, an effect also seen in those following balanced, very-low-energy diets (<800 kcal/day). Since ketosis occurs on both types of diets, though to a lesser degree with very-low-energy diets, it is speculated that ketosis itself may decrease hunger. However, findings from a recent trial suggest that a low-fat vegan diet (10% energy from fat) may be more effective than a ketogenic diet in suppressing appetite.
In controlled trials, low-carbohydrate diets appear no more effective than other diets that similarly restrict calories, nor are they more effective than other dietary interventions, such as low-fat vegetarian diets, at inducing weight loss. A 2013 meta-analysis of randomized controlled trials testing very-low-carbohydrate ketogenic diets (≤50 g carbohydrate/day or ≤10% kcal from carbohydrates) against diets based on modest reductions in fat intake (<30% kcal from fat) for at least 1 year found that ketogenic diets led to marginally more weight loss than reduced-fat diets. However, no statistically significant difference in amount of weight lost was seen between the 2 diets in trials following people for at least 2 years.
At least initially, ketogenic diets may slow fat loss. In a 2016 metabolic study by Hall et al., 17 overweight or obese men were provided a baseline diet (50% carbohydrate, 35% fat, and 15% protein, as a percent of energy) for 4 weeks, then a ketogenic diet (5% carbohydrate, 80% fat, 15% protein) for 4 weeks. For 2 weeks after switching from the baseline diet to the ketogenic diet, participants' weight loss accelerated—but fat loss slowed. The authors attributed the additional weight loss primarily to loss of body water. However, loss of body protein may have contributed; urinary nitrogen levels increased through day 11 on the ketogenic diet. In the final 2 weeks on the ketogenic diet, participants' rates of body weight and fat loss rebounded to a rate comparable to that on the baseline diet. As a result, study participants required 4 weeks on a ketogenic diet to lose the same average 0.5 kg of fat lost in the final 2 weeks on a baseline diet.
I could cite other studies but I wanted to show that there is an abundance of literature about the keto diet and it’s effect on obesity and weight loss. As a cardiac surgeon, I wanted to focus on the negative effects of this diet on your lipid levels which is the primary cause of atherosclerotic cardiovascular disease.
The effect of low-carbohydrate diets on plasma lipid concentrations is a major concern. It has long been established that weight loss by any means causes a reduction in total cholesterol of about 2 mg/dL per kilogram lost. However, low-carbohydrate diets are often an exception to that rule. In a 2002 6-month study of a very-low-carbohydrate “Atkins” diet by Westman et al., 12 (29%) of the 41 participants had LDL-C elevations. The average increase was 18 mg/dL. In a similar 6-month study, 30% of participants had LDL-C increases > 10%. In a trial published in 2003, LDL-C rose 6.2% in a group of low-carbohydrate dieters at 3 months. For comparison, LDL-C dropped by 11.1% during this same time period in participants following a conventional low-calorie diet. In a 2004 1-year study, those on a low-carbohydrate diet increased their mean LDL-C from 112 to 120 mg/dL. In 2018, Hallberg reported a mean 10% rise in LDL-C in individuals following low-carbohydrate diets, an elevation that persisted during 2 years of follow-up.
In the 2002 study cited above, while the mean LDL-C increase was 18 mg/dL, one participant's LDL-C concentration increased from 123 to 225 mg/dL. In the 6 month study, one participant's LDL-C increased from to 219 mg/dL. Another experienced an LDL-C rise from 184 to 283 mg/dL, and a third developed chest pain and was subsequently diagnosed with coronary heart disease. On average, most of the studies showed the standard deviation for the change in LDL-C was 20.4%, indicating that while LDL-C decreased for some, for many participants, LDL-C rose dramatically.
The negative effects on blood lipids have also been seen in healthy individuals. A 2018 pilot study of young, fit adults (average age 31) found that 12 weeks on a ketogenic diet led to a weight loss of 3.0 kg in the ketogenic group, with no significant weight change in the control group. However, despite significant weight loss, LDL-C increased by 35% in the ketogenic group from 114 mg/dL at baseline to 154 mg/dL at 12 weeks.
Some have suggested that LDL-C or LDL particle (LDL-P) concentration elevations are of no concern if the increase is mainly in larger LDL particles. Please understand that any size LDL-P (Advanced Lipoprotein Testing), if present in high concentrations, can enter the artery wall and cause atherosclerosis, leading to heart attacks and strokes. Data supporting this concern come from several studies including the Women's Health Study, a randomized, placebo-controlled trial of low-dose aspirin and vitamin E. As part of the study, LDL particle size was assessed. The hazard ratio for incident cardiovascular disease associated with large LDL particles was 1.44 (indicating a 44% increased risk). For small LDL, it was 1.63 (a 63% increased risk). Both were highly statistically significant. In other words, large LDL particles were strongly atherogenic, albeit less so than small LDL.
It has also been proposed that the risk elevation associated with increased LDL-C concentrations may be neutralized to the extent that the “good” cholesterol (HDL-C) also rises. However, both Mendelian randomization trials and studies using HDL-elevating agents have not shown benefit regarding cardiovascular risk. Treatment-induced HDL-C elevations were examined in a meta-analysis of 108 studies including 299,310 participants, which found no associated reduction in the risk of coronary heart disease events, coronary disease mortality, or total mortality.
In conclusion, keto diets can reduce body weight, although not more effectively than other dietary approaches over the long term or when matched for energy intake. Very-low-carbohydrate diets are associated with marked risks. LDL-C can rise, sometimes dramatically. Pregnant women on such diets are more likely to have a child with a neural tube defect, even when supplementing folic acid. And these diets may increase chronic disease risk: Foods and dietary components that typically increase on ketogenic diets (eg, red meat, processed meat, saturated fat) are linked to an increased risk of chronic kidney disease, cardiovascular disease, cancer, diabetes, and Alzheimer's disease, whereas intake of protective foods (eg, vegetables, fruits, legumes, whole grains) typically decreases. Current evidence suggests that for most individuals, the risks of such diets outweigh the benefits.
For further guidance or medical advocacy, please go to PaladinMDs because “it’s like having a doctor in the family.”
Great article. So important people can see that the risks, which far outweigh the benefits, could actually kill you before the obesity dose. What’s crazy is that there are so many potential diseases you risks trying to get a quick fix and untimely the other diets based on research are not that far off in terms of results. The science and research speak volumes. Thanks for all the input. It’s quite shocking.