Deciding what to eat for optimal health can be confusing. There are so many different dietary approaches, and each is touted as the most beneficial to our health and waistlines, yet the actual nutrition advice often differs greatly or conflicts. It can be difficult to keep up with all the trends and fads, and sometimes it's hard to know who to trust. I'm often asked for nutritional guidance in my clinic, and recently I've been hearing a lot of questions about the ketogenic diet from my patients. Here's exactly what I tell them.
Five things to know about ketosis
Despite its current surge in popularity, the ketogenic diet has been around for a long time and is commonly used for refractory seizure disorders (epilepsy). In fact, evidence of its efficacy for epilepsy dates back as far as 1921. There are many different types of the ketogenic diet,including the classic version, the medium-chain triglyceride (MCT) diet, the modified Atkins diet, and the low-glycemic diet. Because fasting is a rapid method of achieving ketosis, intermittent fasting diets can also be ketogenic depending on how it's accomplished. But what is ketosis? Here are five simple scientific facts that I often give to my patients:
1. In ketosis, human metabolism switches its main energy source from carbohydrates to fatty acids and ketones once the storage form of glucose (glucagon) is used up.
2. In ketosis, the fat cells break down triglycerides into fatty acids, and those fatty acids are used as the energy source by the liver and muscles.
3. The liver cells take the fatty acids and oxidize them into ketones, which are used as the energy source by the brain, muscles, and other tissues.
4. Ketones are in the specific forms acetoacetate, acetone, and beta-hydroxybutyrate. Therefore, checking beta-hydroxybutyrate serum levels is a reliable way to measure ketosis.
5. Physiologically, it does make a difference how one achieves ketosis—whether it's via high fat intake, fasting, or reduction of carbohydrates. For example, if one remains on a high-fat diet for a long period of time and decides to fast a day, ketone concentrations will drop because their body is dependent on the high fat intake.
The ketogenic diet and your brain
Ketosis can be neuroprotective in the short term by improving mitochondrial function, but its long-term effects have not been demonstrated, and I would not consider it a healthy approach to weight loss. In fact, epilepsy patients on the ketogenic diet for seizure control are medically monitored. Side effects can include nausea, vomiting, constipation, fatigue, acid reflux, kidney stones, elevated cholesterol and triglycerides, vitamin deficiencies such as calcium and other water-soluble vitamins, and atherosclerosis.
It's also unclear whether or not the consumption of ketones from foods or drinks packaged with ketones, such as acetoacetate, have similar physiologic effects. Ketones are not found in natural food sources, and the complex metabolic reactions that take place within the body to produce and utilize these ketones should not be oversimplified or undervalued. Ketosis can only be achieved by feeding the body the necessary substrates while avoiding the foods—such as carbohydrates—that counteract the body’s attempts to find and make alternative-energy sources.
Proceeding with caution
Respecting our natural physiology is important. Intermittent ketosis is likely safe and neuroprotective in healthy individuals, but long-term ketosis can cause adverse effects and poor health. Speak with your physician if you're considering making any significant changes to your dietary patterns. And finally, the most important thing we can do is listen to our bodies. If we listen closely enough, we will know what it needs to achieve our own personal optimal health.