By Michelle Lu
Every January, people around the world make New Year’s resolutions, either resolving to continue good practices or accomplish a personal goal. Unsurprisingly, as dieting culture becomes more and more popular, weight loss has become one of the most common New Year’s resolutions. In fact, the Centers for Disease Control reported that in 2013–2016, about half (49.1 percent) of U.S. adults tried to lose weight in the last 12 months.
In particular, the ketogenic (keto) diet has gained much popularity in the last several years. The keto diet is low-carbohydrate, but unlike other low-carb diets that primarily supplant carbohydrates with protein, a keto plan centers around fat. It requires 70 to 80 percent of daily calories to be fat, 5 to 10 percent to be carbohydrate (only about 1 slice of white bread), and 10 to 20 percent to be protein. On the other hand, dietary reference intakes (set by the U.S .Department of Health and Human Services) suggest that adults should consume 45 to 65 percent of their total calories from carbohydrates, 20 to 35 percent from fat, and 10 to 35 percent from protein. People following the keto diet must eat foods high in fat like fish, eggs, dairy, meat, butter, oils, nuts, seeds and low-carb vegetables. “Fat bombs” such as unsweetened chocolate or coconut oil can help people reach their daily goals for fat intake.
So how does a keto diet work? How do people lose weight when having such high fat intake?
The keto diet relies on a process called ketosis, a metabolic pathway that allows the body to survive in a period of famine. The human body generates its energy through a process called cellular respiration. Usually, cells perform cellular respiration by breaking down carbohydrates; hence, carbohydrates are traditionally a crucial nutrient for the human body. However, when glucose storage is low, cells are forced to enter ketosis, during which the body will break down ketone bodies, a type of fuel the liver derives from fat, instead of glucose or other sugars from carbohydrates. The keto diet essentially aims to push the body into this state. How exactly the keto diet promotes short-term weight loss is still unclear. However, some research suggests that it could be because of the increased calorie expenditure due to the metabolic effects of converting fat and protein to glucose, or the satiating effect that high-fat foods generate (which thus decreases appetite and calorie intake).
Despite short-term weight loss results from following the keto diet, many people don’t realize the potential risks associated with it. Most seriously, because of its high saturated fat content, the keto diet is associated with an increase in LDL cholesterol—called “bad cholesterol” because it contributes to fatty buildups in arteries—and higher risk of heart disease. However, it is possible to modify the diet to emphasize foods low in saturated fat such as olive oil, avocado, nuts, seeds, and fatty fish. Other potential risks of the keto diet include kidney stones, constipation (due to lack of fiber from carbohydrate), nutrient deficiencies (due to lack of variety of vegetables, fruit, and grains), and non-alcoholic fatty liver disease (because of the liver’s burden to metabolize so much fat), characterized by storage of too much fat liver cells. Strict diets like this can also lead to social isolation or disordered eating.
In fact, the keto diet was never originally developed for weight loss. Rather, Russel Wilder, a pioneering researcher in diabetes and nutrition, created the diet in 1921 with the primary purpose of managing seizures in children with epilepsy. Epilepsy is a disorder in which nerve cell activity in the brain is disturbed, causing seizures, during which a person experiences abnormal behavior, symptoms, and sensations, sometimes including loss of consciousness.
How can a ketogenic diet help with epilepsy symptoms? To this day, scientists still debate the exact mechanisms of ketogenic diet action. However, there are several popular hypotheses.
One hypothesis regarding the neurological functions of the keto diet is related to changes in neuronal metabolism. In normal conditions, glucose metabolism produces the rapidly available energy that is necessary for seizure activity. However, in patients on the keto diet, blood glucose levels are low, and the brain begins to use ketone bodies for energy. This anaerobic metabolism slows down energy availability, which has been shown to reduce seizure frequency. Another hypothesis is that the keto diet interferes with the concentrations of neurotransmitters. Scientists believe that under a keto diet, brain astrocyte metabolism is more active. This uptick in activity results in enhanced conversion of glutamate, the brain’s major excitatory neurotransmitter, to glutamine, then to GABA, the major inhibitory neurotransmitter. The decrease in concentration of excitatory neurotransmitters and simultaneous increase in concentration of inhibitory transmitters leads to an overall reduction in neuronal excitability, thus contributing to seizure control.
Most people have some awareness that modifying your diet can have wide-ranging physiological effects. However, many may not be aware of the neurological and psychological consequences of dietary changes. While some studies have shown that the keto diet can lead to neuroprotective and disease-modifying effects, low carb diets like keto also often results in disordered eating, which oftentimes means that more weight is gained then lost due to the keto diet. The lack of scientific studies on the keto diet’s long-term effects means that there are still many unknowns for both its benefits and risks.