What is the Ketogenic Diet?
The ketogenic diet is a high fat, low carbohydrate, moderate protein diet. Therapeutic use of the ketogenic diet dates back to the early 20th century for controlling seizures in people with epilepsy. There are theories, however it is still unclear how it helps manage seizures.
When severely limiting intake of carbohydrates, the body relies on fat for fuel by way of ketones and enters a state of ketosis.
This is a very simplistic overview for those interested in how ketosis works.
Nearly 100 percent of carbohydrates break down to glucose—the body’s efficient and immediate fuel source. All cells need glucose for energy and when glucose needs are met, excess glucose is stored as glycogen—about a day’s worth. (If there is more glucose, it is converted and stored as fat.)
When carb intake is severely limited and replaced by fat (or protein), the body uses its stored glycogen to get the glucose it needs. (By the way this is what happens in starvation also.) Once depleted of glycogen, the body relies on protein (food protein or body protein, like muscle) for glucose but for a short time, a few days.
Protein has many important functions and to save it and not ‘waste’ it on creating energy/glucose, ketones come to the rescue. This varies from person to person but usually about three to four days after low carb intake (less than 50 grams, even less than 20g for some people). The liver converts fat to ketones where the body utilizes them as an alternate fuel source. Over time, the body is efficient at metabolizing fat for energy (by way of ketones versus glucose from carbohydrate). This metabolic state is ketosis.
Ketosis forces the body to burn fat for energy rather than carbohydrate. This might seem appealing and you may be wondering—why not?
Short term side effects of ketogenic diet:
- Fruity smelling urine
- Bad breath
- Low-grade acidosis
These effects tend to improve when the diet is continued, as the body adapts to the new diet and adjust the ways in which it sources energy, however there are long term complications that could result.
Long term complications that could result from the ketogenic diet:
- Kidney stones
- Vitamin and mineral deficiencies
- Increased cholesterol
- Decrease in muscle mass
- Loss of bone density
Why do people lose weight?
People lose weight for a few reasons on the keto diet.
- Water weight: The immediate weight loss is water. When depleting the body of glycogen, fluid is lost. For every gram of glycogen we have, we store three to four grams water. Lose glycogen…lose weight! But it’s just water.
- Loss of appetite: The state of ketosis is actually a survival mechanism for those having no access to food, people who are starving. Do you want people to be hungry if they have no access to food? No. Because then they would be foraging for food, increasing metabolism. So ketosis may actually slow metabolism in addition to suppressing appetite.
- Limited food choices: Like the heyday of the Atkins diet people lost a lot of weight! Was it the magic of Atkins? Weight loss was partly due to numbers 1 and 2 above but also fewer choices. If a restaurant meal may include a steak, baked potato with cheese, sour cream, butter, and bacon, plus dessert and you take away the loaded baked potato and dessert (because they’re carbohydrates), of course weight will be lost. Similarly the ketogenic diet works by eliminating entire food groups. Limited food groups, limited choices may lead to weight loss.
Is it sustainable?
It’s a diet. Some people do okay with the limitations, others not so well. In one meta-analysis of 13 randomized controlled trials, there was a nearly 40 percent dropout rate. Remember, each person is different. The ketogenic diet may be useful for a small percentage of individuals with specific health needs. But with any nutrition plan the plan needs to be created for each individual to get the best results.
Bueno, NB et al. British Journal of Nutrition (2013), 110, 1178–1187 Very low carbohydrate ketogenic diet versus low fat diet for long term weight loss: a meta-analysis
Veech, Richard L. “The therapeutic implications of ketone bodies: the effects of ketone bodies in pathological conditions: ketosis, ketogenic diet, redox states, insulin resistance, and mitochondrial metabolism.” Prostaglandins, leukotrienes and essential fatty acids 70.3 (2004): 309-31.
E. F. Hobdell and L. Tonyes, “Diets for epilepsy,” Touch Briefings: US Pediatric Review, vol. 2, pp. 45–46, 2007 “Short-term adverse effects include dehydration, mild metabolic acidosis. Long-term adverse effects include nephrolithiasis, constipation, vitamin and mineral deficiencies, increased cholesterol, retarded growth in young children, and decreased bone mineral density”