By Rachel Stuck, RDN
If the keto diet were an ice cream flavor, it would probably be pistachio—you either love it or you grimace when you see it listed on the ice cream parlor menu. Now imagine that pistachios start showing up on the morning news and talk shows, and that your Pinterest page is flooded with pistachio meal ideas and infographics detailing its so-called miracle properties. You can understand how the pistachio lovers would be thrilled to see their favorite flavor finally getting the recognition it deserves and the pistachio haters would start to loathe the mere mention of this flavor. This seems to be where keto currently stands. Either you love it or you despise another restrictive diet trend showing up everywhere you look.
If you haven’t heard about keto yet, here’s a quick rundown. The ketogenic or “keto” diet is a high-fat style of eating; dietary fat accounts for a majority of daily calories, there’s a moderate intake of protein, and a very low intake of carbohydrates. While the definition of a ketogenic diet can vary, a typical macronutrient breakdown might look something like this:
Someone following a 2,000-calorie-per-day diet would have a caloric breakdown that looks like this:
This means a keto diet will contain mostly high-fat foods like:
Remember, a 2,000-calorie diet with 75% of calories coming from fat translates to 215 grams of fat per day. That’s almost 1 cup of olive oil or 8 medium avocados.
The idea behind the high-fat diet is to deprive the body of glucose, its main source of energy, and push it to use an alternative energy source—fat. Ketones are what your liver produces from fat when your body is deprived of adequate energy from glucose. This process is known as ketosis, which is the goal of the keto diet. Ketosis can also happen due to untreated type 1 diabetes, or during periods of starvation, low food intake, intense exercise, or alcoholism.
After just a few days of following a ketogenic diet, an individual may notice significant weight loss. This is because glucose, our main energy source, is stored as glycogen and water. When the glycogen stores have been depleted, the number on the scale will also go down because the body has not only depleted glycogen stores, but also the water that was stored with it. This leads dieters to believe the high-fat diet is quickly burning away their fat stores, which is not actually the case. If the ketogenic diet is continued, fat loss will follow, but unfortunately, the water and glycogen weight will return as soon as carbs are reintroduced and the body is out of ketosis.
Weight loss seems to be the most recent claim to fame for the ketogenic diet, but before becoming a popular diet trend, the ketogenic diet was well known to the medical world. Doctors found the ketogenic diet to be a beneficial way to manage the symptoms of neurological disorders like epilepsy, multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, chronic headache, sleep disorders, and neurotrauma.(1)
Even dieters who don’t suffer from the above ailments have noted keto’s bonus effect of increasing mental clarity and reducing brain fog. Some studies have noted its positive impact on diabetes, metabolic disorders, and cholesterol. One study concluded that following a keto-style diet for sixteen to twenty-four weeks not only significantly reduced participants’ body fat and body mass index (BMI), it also decreased “bad cholesterol” (LDL cholesterol), triglycerides, and blood glucose levels.(2)
After reading about the benefits of following the ketogenic diet, you might be thinking, “Hmm... maybe I should give this a try.” But, before you load your pantry with olive oil (you’ll need the big bottle), butter, and avocados, let’s talk about where the diet might be lacking.
The main shortcoming of the ketogenic diet is that it is extremely low in fibrous foods like fruit, whole grains, and legumes, and it even limits vegetables. These plant-based foods have, time and time again, has been proven to prevent disease, making them a crucial part of a balanced diet.(3) Reducing fruits, vegetables, and grains (and therefore fiber), not only reduces the
It is important to note that there is a rift in the keto community. The divide exists between “clean keto” and “dirty keto” camps, who disagree about which foods should be eaten to reach ketosis. The clean keto approach focuses on including fat from quality sources like olive oil, avocados, grass-fed meat, and nuts. The dirty version might include processed foods like pork rinds and bacon, and additional added fat from cheese and high-fat, commercially raised meat. Unfortunately, most of the research about high-fat diets does not distinguish between “clean” keto and “dirty” keto. Adding to the confusion, high-fat diet studies are often animal studies, making it challenging to draw a sound conclusion without further research.
There is not an extensive body of research about the effects of a clean ketogenic diet on the gut microbiome. We found that most of the research on a high-fat diet and the gut microbiome includes a small sample size or the high-fat diet is coupled with sugar or processed carbohydrates. This makes it challenging to form a clear understanding of how the ketogenic diet affects the health, diversity, and function of the gut microbiome.
To start, here are four studies that suggest gut microbiome diversity is altered after a shift toward a high-fat diet. Each article shows slightly different findings depending on how the study defines a high-fat or ketogenic diet. You will see that when the high-fat diet includes mostly animal-based fats and minimal plant foods, more negative outcomes are found than in a high-fat, low-carb eating style that includes a variety of plant fibers from non-starchy vegetables.
There are numerous ketogenic-adopting athletes who are excited to share their successes with keto, but are exercise and restrictive dieting a good match? Exercise puts stress on the body, and restricting energy sources can cause additional stress, leading to poor workouts or even injuries. If you are active, it’s best to follow a balanced diet that includes nutrients to replenish, build, and heal the body before and after exercise.
A small amount of research supports endurance athletes following a high-fat, low-carb diet, but athletes participating in high-intensity sports that require short bursts might see a drop in performance.(9) When athletes start a high-fat diet, there is an (often frustrating) seven- to nine-month period during which they may not be able to perform at a high level. That being said, it is safe to conclude that a varied diet with moderate carbohydrates might be the most realistic way for an athlete to reach peak performance without lost training time related to the adaption period.
Following a ketogenic diet takes a lot of dedication and can be challenging because it requires so much planning and willpower. It takes the body a few days to truly be in ketosis and then once you're in it, just one meal can sabotage your hard work. When you follow a ketogenic diet, holidays, parties, or nights on the town become obstacles instead of celebrations, especially if you are looking for long-term results.
Although the benefits of a ketogenic diet are valid, completely breaking up with carbohydrates is tough and, more importantly, can be detrimental to your gut bacteria. Following a varied diet with a balanced addition of carbohydrates from vegetables, fruits, whole grains, and legumes can help you achieve sustainable weight loss and ensure that the population and diversity of your gut bacteria is supported.