Pros and Cons of the Keto Diet
Pro: Weight Loss, Cravings, and Hunger
The keto diet is probably best-known as a weight loss diet, and with good reason.
When you eliminate virtually all carbohydrates, your body is literally forced to burn more fat for fuel, including stored body fat. This is excellent for weight loss. Additionally, the ketones your liver produces in response to carb restriction can reduce food cravings and blunt appetite.
Research shows the keto diet is one of the few diets with which obese people can lose weight without counting calories or intentionally restricting food intake. While you do have to count and limit carbohydrates, one of the biggest strengths of keto is that most people can eat as much as they want (minus carbs) and still lose a reasonable amount of weight.
All bodies are different, and not everyone is able to “keto-adapt” to a very-low-carb diet, but the current evidence suggests keto may be highly effective for people who struggle with overeating, or who usually have problems sticking to restrictive diets.
Pro: Metabolic Health
When you eat carbohydrates, your pancreas releases insulin to help metabolize the carbs in the form of glycogen (stored sugar). But for some people, over time, their tissues become less sensitive to insulin, which results in a vicious cycle: blood sugar rises to dangerous levels and the pancreas, which is then required to produce more insulin, becomes strained, and cells’ healthy insulin response is further impaired.
Because it involves carb restriction and because of its effects on weight loss, the keto diet appears to be effective for improving metabolic health.
Evidence suggests restricting carbs a la keto can reduce blood sugar, decrease insulin resistance, and sometimes even allow people with type 2 diabetes to become less dependent on medications like insulin shots.
Pro: Brain and Neurological Health
The keto diet may benefit brain and neurological health in two distinct ways.
First, because it involves carb restriction, your blood glucose levels are lower on average if you follow keto compared to most ways of eating. High levels of glucose are inflammatory and can cause damage to nervous system cells, so lowering your glucose levels can sometimes be beneficial for brain health.
Second, the actual ketones your body produces when you restrict carbs also appear to have anti-inflammatory benefits for the brain and central nervous system. Your brain can also use ketones for fuel, so in some dementia-like conditions, evidence suggests going keto can help provide your brain with a high-energy fuel that boosts cognition.
Con: The Keto Diet Is Very Restrictive
If you dislike reading labels, the ketogenic diet probably isn’t right for you.
Eating too many carbs prevents your body from going into ketosis. To ensure ketosis, it’s necessary to read labels and count or track net carbs (by subtracting the dietary fiber from “total carbs” on food labels).
A single mistake or impulsive decision around carb intake can take you out of ketosis, at which point it takes another 12-36+ hours of strict compliance for your body to begin producing ketones again.
Most people must keep their net carb intake around approximately 20 grams of carbs per day to achieve and maintain ketosis. People with a higher body mass index or who are more active may be able to consume up to 50 grams of net carbs per day.
Practically speaking, this means you’ve got to exclude foods that are high in carbs. On the positive side, keto entails avoiding a lot of ultra-processed foods high in sugars and refined starches. But it also excludes or severely limits plenty of grains and healthy fruits and veggies due to their carb content.
Con: The Keto Diet Isn’t Flexible
As outlined above, deviating from the standard ketogenic diet and consuming excess carbs will cause your body to exit ketosis for up to a day or longer until you start producing ketones again.
But there could also be other consequences to “cheat days” on keto. In a small, 2019 study of 9 healthy young men, researchers found that consuming 75 grams of sugary carbs after following keto for seven days resulted in increased damage to the endothelium (delicate lining) of blood vessels compared to the same amount of carbs consumed prior to going keto.
While a strict keto diet appears to reduce problems associated with insulin resistance and type 2 diabetes, this finding suggests that it may increase the body’s vulnerability to hyperglycemia (high blood sugar) from carb binges.
Whether or not this is the case, it’s not a good idea to follow a restrictive diet only some of the time. The pattern of following a strict diet, then binging “cheating” with foods that aren’t allowed, also called “yo-yo dieting,” is linked with poor health outcomes.
Con: Athletic Performance
For most athletes, a strict ketogenic diet isn’t the best choice for physical performance.
Your muscles rely on several different metabolic pathways for energy during exercise. When you go on a very-low-carb keto diet, the anaerobic pathways involved in supplying most of the energy for the first 60-90 seconds of intensive physical activity are deprived of a primary fuel source, glycogen (stored sugar).
Instead, the keto diet emphasizes the less powerful endurance-oriented aerobic oxidative pathway at the expense of anaerobic carbohydrate metabolism. While this can be great for burning fat, it’s not ideal for most competitive athletes or others who require peak physical performance.
Limited research does suggest that some athletes may be able to use keto for short periods of about 30 days as a weight loss method without impairing fitness, but it’s not a good choice as a year-round diet to support overall athletic performance.
Con: “Dirty Keto”
“Dirty keto” is a modified keto diet that prioritizes restricting carbs to achieve nutritional ketosis above making healthy food choices.
In other words, on dirty keto, you can eat as much ultra-processed food (or any food) as you want as long as you restrict net carbs to 20 grams per day or less (for most people).
The appeal of this type of keto diet is that you can lose weight, at least in the short term, and still eat certain types of fast food and junk food while watching your carbs.
There’s currently no peer-reviewed evidence on how well dirty keto works (or doesn’t work) to lose fat, but perhaps needless to say, it’s not a good idea to focus on weight loss at the expense of well-rounded nutrition.
Unlike standard keto, dirty keto tends to lack fiber, healthy vegetables, and other important sources of micronutrients, and is instead full of synthetic preservatives, artificial coloring, artificial flavorings, omega-6 fats, and low-quality sources of fats and protein.