What is a Ketogenic Diet and is it Healthy?

Reviewed by Dr. Jonathan Bonnet, MD, MPH, Judy Singer, RD and Heather Hodson, RD

Low-carbohydrate diets have had a longstanding run in the American spotlight. When the Atkins Diet first gained widespread popularity in the 1990s, devotees began swapping their morning bowl of cereal for plates of eggs, cheese, and bacon.

Though the Atkins Diet may have fallen out of favor in recent years, another high-fat, low-carb alternative has taken its place: the ketogenic, or keto, diet. People of all ages, genders, and health histories have tried the keto diet to lose weight or manage a chronic health condition. But what does the science say about the safety and efficacy of this dietary approach?

Here, we explain what a ketogenic diet is, the evidence behind its claims for benefiting your health, and whether or not it may be right for you.

What is a ketogenic or “keto” diet?

At its core, a ketogenic diet is one that is high in fats, moderate in proteins, and very low in carbohydrates. Someone on the average ketogenic diet gets at least 70% of their calories from fats, around 20% from proteins, and less than 10% from carbs.

Another rule of thumb for someone following a ketogenic diet is to limit their intake to between 20 and 50 grams of net carbohydrates a day. (To measure net carbohydrate intake, you count the total grams of carbs consumed minus the total grams of fiber consumed.) For reference, the average apple has around 25 grams of carbohydrates.

Ultimately, the goal of a ketogenic diet is to drive its dieter into a state called ketosis, where the body uses predominantly fat and ketone bodies as its primary energy source rather than glucose. These ketone bodies are the same fuel utilized during periods of fasting.

There are no specific foods that cannot be consumed on the keto diet. But because of the marked restriction of carbohydrates required to get into ketosis and remain there, it can be challenging to include substantial amounts of otherwise healthy foods that are higher in carbohydrates such as some grains, vegetables, and fruits. Many of these higher-carb foods are excellent sources of many vitamins and minerals; restricting them may in turn decrease overall daily intake of these nutrients.

Why do people go on ketogenic diets?

The ketogenic diet was first used in the early 20th century as a therapeutic diet to treat epilepsy in children. Though the severity of its restrictions made it difficult for many children to follow long term, it did help to manage the condition for some in the short term. Once antiepileptic agents were developed and introduced to market, the diet largely fell out of therapeutic use for pediatric epilepsy.

Decades later, the ketogenic diet resurfaced in popularity as a strategy for rapid, short-term weight loss. Additional reasons why some may try a ketogenic diet include:

  • Manage type-2 diabetes (including reducing the need for medication)

  • Reduce diet-related hunger cravings

  • Reduce insulin resistance

  • Improve blood glucose balance

  • Retain lean muscle mass

  • Prevent and treat certain neurological disorders

Is eating that much fat bad for my health?

People on a ketogenic diet consume higher quantities of fat, including saturated, monounsaturated, and polyunsaturated fats. The general recommendations are that monounsaturated fats are generally health supporting. Many polyunsaturated fats (particularly omega-3s) are also "good," though this is a little more nuanced.

For many years, a high intake of saturated fat was associated with a higher risk of cardiovascular events. To this day, many people still avoid high-fat foods like cheese and butter in an attempt to benefit their heart health. But research on this front is changing.

Specifically, there is some evidence that a ketogenic diet can improve blood lipids (including HDL and LDL), though this research is mixed. One review from the National Lipid Association found that while a ketogenic diet may improve HDL in the first year, these benefits are unlikely to last.

In other studies, LDL cholesterol increased on a keto diet, while others showed no changes in LDL levels.

Overall, saturated fat may not be as bad as we think, but the source of the fat does matter. For some people saturated fat can really elevate LDL levels. For those people, they should avoid saturated fat.

Importantly, the research we have on the benefits and risks of a ketogenic diet are limited to short term findings. More research is needed to determine the safety and possible risks of a ketogenic diet on long term health.

Is it safe?

Research largely suggests that ketogenic diets and reaching a state of ketosis is safe for most people in the short term.

However there are some risks to consider when implementing a ketogenic diet:

  • Temporary side effects can include:

    • Nausea

    • Vomiting

    • Headache

    • Fatigue

    • Dizziness

    • Insomnia

    • Difficulty in exercise tolerance

    • Constipation

  • Long-term adverse effects can include:

    • Hepatic steatosis

    • Hypoproteinemia

    • Kidney stones

  • Vitamin and mineral deficiencies

  • The possibility of developing ketoacidosis in those with an underlying predisposition (including alcoholism, insulin deficiency, or people on SGLT-2 inhibitors)

  • Developing a poor relationship with food or disordered eating patterns

Will I benefit from a ketogenic diet?

Existing research suggests that ketogenic diets may be beneficial for those with type 2 diabetes or obesity. Regardless of your situation, you should always consult with a doctor or dietitian before starting a ketogenic diet. This is especially important if you take insulin for type 2 diabetes as it may require a medication adjustment.

When considering a ketogenic or other restrictive diet, it’s important to weigh the benefits against its potential risks. As with other diets or weight loss interventions, sustainability is crucial. Finding strategies that you can stick to in the long run is essential to identifying a lifestyle change that can grow with you over time.

Ultimately, while many people may benefit from a lower carbohydrate diet, not everyone may benefit from the more severe restrictions of a ketogenic diet. And, if you plan to reintroduce carbohydrates, you may regain the initial water weight that you lost.

Deciding whether or not to try a ketogenic diet is a highly personal question and one that can benefit from the guidance of a healthcare provider. If you’re unsure about where to start, Forfend can help. Our whole person exams can help you optimize your approach to whole body wellness.


Comparison of Group Medical Visits Combined With Intensive Weight Management vs Group Medical Visits Alone for Glycemia in Patients With Type 2 Diabetes. (2019).

Effect of low carbohydrate high fat diet on LDL cholesterol and gene expression in normal-weight, young adults: A randomized controlled study. (2018).

Emerging Concepts: Type 2 Diabetes and the Ketogenic Diet. (n.d.).

Ketogenic Diet. (2021).

Review of current evidence and clinical recommendations on the effects of low carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: A scientific statement from the National Lipid Association Nutrition and Lifestyle Task Force. (2019).

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