Extremely low in carbohydrates, but high in fat: the ketogenic diet promises rapid weight loss through the metabolic state of ketosis. But is it healthy at all and does it help you lose weight in the long term – and what about the environmental balance?
The ketogenic diet is an extreme variant of the low carb diet, in which less than 30 grams of carbohydrates are consumed per day. As early as the 1970s, it was promoted by cardiologist Dr. Robert Atkins for weight loss. In the meantime, various keto variants exist, in which about two-thirds to 90 percent of the daily energy requirement is covered by fat and about 6 to 8 percent by protein. According to studies, the keto diet could have a positive effect on epilepsy and a negative effect on cardiovascular health.
Most of the body’s cells are able to switch to other energy substrates, such as fatty acids, when glucose is deficient – not so the brain, erythrocytes and nerve cells. They depend on a steady supply of glucose. Therefore, when starting a ketogenic diet, the body first begins to compensate for the carbohydrate deficit by emptying the carbohydrate stores in muscles and liver and driving gluconeogenesis.
Once glucose stores are depleted, fat is resorted to as the primary energy substrate. Fatty acids that are released are enzymatically converted to acetoacetate, 3-β-hydroxybutyrate and acetone. The physiological metabolic state of ketosis must be distinguished from pathological ketoacidosis, a severe metabolic derailment that can occur in poorly controlled diabetes patients.
Effect on energy metabolism unclear
In the first phase of a ketogenic diet, the metabolic change initially leads to an increased energy metabolism of the body, presumably due to the increased hepatic oxygen demand for gluconeogenesis and triglyceride fatty acid recycling. How the keto diet affects the body’s energy expenditure in the long term, however, remains unclear due to a lack of long-term follow-up studies, he said. This is reported by a research team led by Wajeed Masood, Pavan Annamaraju and Kalyan R. Uppaluri. in a review in the journal Nutrients.
However, the studies allow conclusions to be drawn that the energy metabolism decreases again after the metabolic change. The researchers explain this with the so-called adaptive metabolic mechanism, which leads to a reduction in resting metabolic rate after weight loss to regulate the imbalance between energy intake and consumption.
Less frequent epileptic seizures on the keto diet
The influence of the keto diet on the frequency of seizures in epilepsy patients has been better studied. Particularly in children, it can reduce them – if strictly adhered to – by more than 50 percent. This is shown in a review article in the “European Journal of Clinical Nutrition”, for which a research team led by Dr. Yue Ruan from the University of Lanzhou, China, evaluated 24 systemic reviews and meta-analyses with a total of 255 individual studies on the subject.
A 2020 Cochrane review reached similar conclusions. According to this review, the health benefits of the keto diet were seen primarily in pediatric epilepsy patients: Those on a strict ketogenic diet were up to three times more likely to become seizure-free than those on a non-ketogenic diet. Those on the keto diet were even up to six times more likely to have at least 50 percent fewer seizures.
According to the Cochrane review, adult epilepsy patients on a ketogenic diet did not usually achieve freedom from seizures, but the probability of at least a 50 percent reduction in the frequency of seizures was up to five times higher in this age group than with a non-ketogenic diet. The explanation for the protective effect is thought to be that the ketone bodies inhibit the mTOR signaling pathway, which plays an important role in the development of epilepsy.
Increased LDL cholesterol levels
However, as a diet rich in animal products and fat, the keto diet may increase LDL cholesterol levels. This could be associated with up to a twofold increased risk of future cardiovascular events. That’s suggested by an observational study using data from UK Biobank, the results of which were presented March 5 at the World Congress of Cardiology in New Orleans by lead study author Dr. Iulia Iatan of the University of British Columbia in Vancouver, Canada.
“Hypercholesterolemia that occurs during a low-carbohydrate, high-fat diet should not be considered harmless,” Iatan said. Criticizing the study results was Dr. Steven Nissen of Cleveland Clinic in Ohio. The people who followed a keto-like diet in that study “were overweight for a reason” and differed from those who followed a standard diet, he said: They would have had a higher average body mass index (27.7 versus 26.7), and the incidence of diabetes was higher (4.9 versus 1.7 percent). Accordingly, their risk profile differed from that of the study participants who did not follow a ketogenic diet.
Popular Keto Foods:
- Salmon
- Olive oil
- Coconut oil
- Avocado
- Eggs
- Chicken
- Beef
- Nuts
High CO2 footprint
In terms of sustainability, the keto diet doesn’t score: with an estimated almost three kilograms of CO2 generated per 1000 kilocalories consumed, it is one of the most environmentally damaging diets. By comparison, a vegan diet consumes only about 0.7 kilograms of CO2 for the same number of calories. That’s according to a team led by Professor Keelia O’Malley, Ph.D., of Tulane University in New Orleans, in the American Journal of Clinical Nutrition (DOI: 10.1016/j.ajcnut.2023.01.009). The study included data from more than 16,000 adults. The increased CO2 consumption of the keto diet can be explained by the many animal foods.
In addition, O’Malley and colleagues also associated the ketogenic diet with increased LDL cholesterol levels. They also attested to its poor nutritional quality, as measured by the so-called Healthy Eating Index (HEI). The HEI is a measure that can be used to compare different diets in terms of their health effects. The keto diet scored the worst with 44 out of 100 points; the best score was 59 points for the pescetarian diet, which avoids meat but not fish, eggs and dairy products.
Keto diet risks nutrient deficits
The keto diet also scores poorly on the HEI because its limited food selection carries the risk of nutrient deficiencies. It does not correspond to the nourishing recommendations of the German society for nutrition (DGE), which recommends for instance also fiber-rich whole grain products for a full nutrition. To prevent deficiencies and health complications, it is therefore advisable to discuss a planned keto diet with your doctor in advance and to have your nutrient status monitored regularly.