Ketogenic Diet 101: A Beginner's Guide

Fat is back in this ultra-low-carb, high-fat diet. Find out what foods you can eat on the keto diet plan, if the keto diet could work for you and what you can expect if you limit carbs and embrace fat.

After years of being restricted to therapeutic nutrition in hospitals, the ketogenic diet (typically called the keto diet) is back as one of the hottest diet trends in America.

The diet originated back in the 1920s as a way to treat childhood epilepsy, and due to its striking success rate—people eating a keto diet experience about 30% to 40% fewer seizures—it's still used in that field today.

But what about its use for the general healthy population just looking to lose some weight or get more out of life? Let's unpack this ultra-low-carb, high-fat diet bit by bit.

Read More: I Tried the Ketogenic Diet for 30 Days and Here's What Happened

What Is the Keto Diet?

The ketogenic diet is super high in fat (about 80% of your daily calories), super low in carbohydrates (less than 5% of your calories) and moderate in protein (typically 15% to 20% of your calories). This is a pretty drastic departure from the generally recommended macronutrient distribution of 20% to 35% protein, 45% to 65% carbohydrates, and 10% to 35% fat.

The most important component of the keto diet is a natural process called ketosis. Normally, bodies run very well on glucose. Glucose is produced when the body breaks down carbohydrates. It's a very simple process, which is why it's the body's preferred way to produce energy.

When you cut back on carbs or just haven't eaten in a while, your body looks for other energy sources to fill the void. Fat is typically that source. When your blood sugar drops because you're not feeding your body carbs, fat is released from your cells and floods the liver. The liver turns the fat into ketone bodies, which your body uses as its second choice for energy.

What Foods Can You Eat on the Keto Diet Plan?

a printable list of various foods that are Keto Diet Friendly

A typical keto diet plan consists largely of:

  • Meat
  • Fish
  • Butter
  • Eggs
  • Cheese
  • Heavy cream
  • Oils
  • Nuts
  • Avocados
  • Seeds
  • Low-carb green vegetables

This short list leaves out carb-heavy foods, such as grains, rice, beans, potatoes, sweets, milk, cereals, fruits and even some vegetables.

What Are the Potential Benefits of the Keto Diet?


Featured Recipe: Salmon-Stuffed Avocados

While the keto diet certainly is not easy, research shows it has some potential therapeutic benefits in addition to its use for treating epilepsy. Here are some areas of research where a keto diet shows promise:

Alzheimer's Disease

A 2019 study in the International Journal of Molecular Sciences suggests that when patients with Alzheimer's eat a ketogenic diet, cognitive function significantly improves. It's believed that this has something to do with improving mitochondrial function by providing the brain with new fuel.

Parkinson's Disease

One of the key features of Parkinson's disease is the abnormal accumulation of a protein known as alpha-synuclein. Research funded by the Michael J. Fox Foundation for Parkinson's Research has explored whether a ketogenic diet stimulates the breakdown of these proteins, reducing the amount of alpha-synuclein in the brain.

Multiple Sclerosis

In a small 2022 study published in Neurology, patients with relapsing multiple sclerosis (MS) were put on a ketogenic diet. After six months, they reported improved quality of life, as well as physical and mental health improvements. Before doctors or researchers can make a connection between keto and MS, they need bigger sample sizes and more thorough research. Still, the preliminary findings are exciting.

Cardiovascular Disease

This is a point of confusion and controversy since a diet that relies so heavily on meat and fat is naturally thought to raise blood cholesterol and cause heart issues. However, some evidence suggests that this may not be the case. In fact, the keto diet may help improve triglyceride, HDL and LDL levels. A 2022 review published in Nutrients looked at all of the available evidence around the ketogenic diet and cardiovascular health and found that the diet may be associated with some improvements in cardiovascular risk factors. Mind you, the authors also expressed their concerns with maintaining the diet in the long term, and they proposed that these benefits may not be long-lasting. It's clear that we need long-term studies to fill that gap.

Type 2 Diabetes

This population has been studied heavily with the keto diet since it's technically as low-carb as you can get. While the research to date has been conducted in very small sample sizes, evidence suggests that an ultra-low-carb diet (like the keto diet) may help reduce A1C levels and improve insulin sensitivity by as much as 75%. In fact, a 2020 review published in Nutrition & Diabetes found that a keto diet was associated with better glucose and lipid control and weight loss. Having said that, more research is needed.


Early experimental research suggests that the keto diet may have anti-tumor effects, likely because it reduces overall calorie intake (and circulating glucose) for tumor growth. However, not all tumors respond to the effects of a ketogenic diet, as noted in the Current Opinion of Clinical Nutrition and Metabolic Care in 2019. Other research studies, such as the randomized controlled study involving rats published in Cancers in 2018, suggested that the ketogenic diet had minimal impact on tumor growth in the liver. More research on humans with larger sample sizes is needed, but it's definitely food for thought.


Featured Recipe: Parmesan Spinach Cakes

Can the Keto Diet Plan Help with Weight Loss?

This is one of the keto diet's main selling points and a primary reason it's so popular—the keto diet proponents say you can drop a lot of weight in a relatively short period of time. But is that too good to be true?

Several studies, including research published in the Journal of Strength and Conditioning Research in 2018, cited that following a low-carbohydrate diet (like the keto diet) may result in weight loss without compromising athletic performance. Promising, right? Well, weight loss is only good if that momentum is sustainable long-term, and it's not clear that that's the case.

A 2020 review from Cureus suggested that those who followed the ketogenic diet may have have experienced weight loss and showed improvement in blood pressure, triglycerides and good (HDL) cholesterol levels. However, these improvements were not observed beyond the 12-month mark, suggesting more long-term studies are needed to confirm the diet's effectiveness.

Still, let's look at some reasons why keto may work for some as a weight loss tool.

  • Calorie Restriction: When you severely restrict your food intake by cutting out many categories of food, you're quite likely to lose weight.
  • Water Loss: There is some evidence that higher-protein diets like the keto diet may have some weight loss benefits, partially because both fat and protein are satiating, so you don't feel hungry, but also because of the loss in glycogen stores. Glycogen is the body's glucose storage that is bound up with water, so when we deplete the glycogen, we also deplete our water storage. Lose a ton of water, and you're going to drop weight fast.
  • Appetite Control: In addition to the satiating capabilities of fat and protein, 2021 research published in Current Opinion in Clinical Nutrition and Metabolic Care suggests that the keto diet may help suppress the hunger hormone, ghrelin. For people who are always hungry, this can be beneficial to weight loss.

Read More: 30 Healthy Low-Carb Foods to Eat

What Are the Downsides of the Keto Diet?

Unfortunately, it can't all be rainbows and unicorns. Here are some potential side effects and dangers of eating keto.

Athletic Performance Impediments

For those people who train heavily and hard, going keto might cramp your style. As important as protein is for muscle growth, carbs also play an equally critical role by releasing insulin to drive that protein into muscles faster. It also helps us build up glycogen stores for longer training sessions, runs or hikes. One comprehensive review of the literature in sports nutrition found that while research is lacking on the long-term impacts of the keto diet, in the short term, the keto diet is inferior to other diet protocols on anaerobic, aerobic and in some cases even strength performance measures.

Keto "Flu"

Your body isn't accustomed to using ketones regularly, so when you make the switch, you tend to feel unwell. A 2019 study published in Nutrients suggests the keto diet may also influence electrolyte balance, resulting in brain fog, headaches, nausea and fatigue. People on the keto diet also consistently complain about getting bad-smelling breath, sweat and pee as a result of the by-product of fat metabolism (acetone) seeping out. Thankfully, this effect is temporary, so just know you won't have to spend your life smelling rank.


No one likes to feel backed up and sadly, if you're not careful about your diet choices when going keto, it could become a regular concern. Since you're cutting out whole grains and fruit (two of the most common sources of fiber), aim to up your fiber-rich veggies, and consider a supplement.

Nutrition Deficiencies

As with any super-restrictive regimen, when you cut food out, there's a good chance you'll be missing something big. Here's what you need to keep an eye open for.


Believe it or not, depending on your diet, you may be low on salt. When carb intake is low and insulin isn't being excreted, the kidneys absorb less sodium and potassium and excrete more as waste, leaving you feeling dizzy, fatigued and grumpy. Rather than reaching for more processed food, try seasoning your food a little more liberally with sea salt.


With the approved list of foods being so brief, you might not get enough fruits and veggies on keto. One of the biggest impacts? A potassium deficiency—and all of the lovely constipation and muscle cramps that accompany it. Aim to up your intake of foods like spinach, avocado, tomatoes, kale and mushrooms to get your potassium fix.

Vitamin C

Most of our vitamin C intake comes from a nice array of fruits, so if you're cutting all of that out, you'll have to make sure you're keeping your veggies up to compensate. Reach for more broccoli, Brussels sprouts, cauliflower and cabbage to ensure you get your fill.

Brussels Sprouts with Vermouth & Bacon
Greg DuPree

Featured Recipe: Brussels Sprouts with Bacon & Vermouth

Disordered Eating

As with all restrictive eating patterns, the keto diet certainly can interfere with your relationship with food. Overly restricting or removing whole food groups from your diet has the very real power to encourage orthorexic tendencies and an unhealthy obsession with what to eat.

It also interferes with some of the social aspects of food, considering how limiting it is. No cake on your birthday. No pie on Thanksgiving. No chocolate truffles on Valentine's Day. Boo to that! If you consider yourself someone who loves to eat and takes great joy in the social experience of a good meal, then the restriction of this diet may be emotionally unhealthy.

Read More: What Is Intuitive Eating?

Who Shouldn't Do the Keto Diet Plan?

Before starting any new diet, you should always clear it with your health care provider first. This is particularly true for certain groups for whom the keto diet may not be a healthy idea. These include (but are not limited to):

  • People with gallbladder or pancreatic issues: Fat is more difficult than other macronutrients for the body to digest, so this may be a strain for those with gallbladder or pancreatic disease.
  • Pregnant and breastfeeding women: While research is in its infancy, early animal models in a 2020 study published in Diabetes, Metabolic Syndrome and Obesity suggest some of the metabolic changes that occur during ketosis that may impact fetal growth. This time of your life is not the time to risk undernourishing yourself, as nutritional deficiencies and extreme weight loss may reduce milk supply and stunt infant growth.
  • Healthy children: Childhood is never a time for dieting, never mind an extreme diet like the ketogenic diet.
  • People with kidney issues: Those who are prone to kidney stones may want to avoid the keto diet due to the shifts in sodium, potassium and fluid balance.
  • People with a disordered eating history: As previously mentioned, the keto diet is extreme, and any type of diet that severely restricts or limits foods may perpetuate disordered eating thoughts.
  • Bariatric or gastrointestinal surgery patients: Patients with limited digestive capacities should avoid the keto diet since fat is particularly difficult for the body to digest.

The Bottom Line on Keto

From reviewing keto research and literature, it looks like we're just scratching the surface of understanding some of the potential therapeutic roles of the keto diet. While it's unclear if it's any better or worse than any other diet for weight loss, the reality is that there is no one-size-fits-all model for diets. This doesn't even consider that weight loss diets, in general, don't really work. While researchers can't agree on a specific statistic, it's commonly accepted that most people on the keto diet will regain the weight lost (and often pack on extra pounds, as well). The long-term outcome of the keto diet is likely to be no different, especially given how challenging and restrictive it is to maintain.

Our advice? If you like carbs, don't swear them off entirely. Choose healthy carbohydrates more often and learn ways to choose the most satiating versions of them to fuel you. And if you want to try keto, get in touch with a registered dietitian to help you work through the diet in a healthy manner.

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