The ketogenic, or keto, diet is high in fat and low in carbohydrates. However, some types of fat bring health risks, including heart disease. Healthful fats for keto include olive oil, avocado oil, nuts, and seeds.
People on the keto diet need to get 55%–60% of their daily calories from fat in order to stay in ketosis. This means that a person consuming 2,000 calories per day needs approximately 122–133 grams (g) of fat daily.
In this article, we will look at the more healthful fats to include in the diet and which ones to limit.
Many researchers still debate the health risks and benefits of different fats.
The Dietary Guidelines for Americans 2015–2020 recommend limiting sources of saturated fat, such as red meat, butter, and dairy, due to their links with heart disease.
However, a 2016 meta-analysis indicates that butter has only a small association with mortality, cardiovascular disease, and diabetes.
What is clear is that unsaturated fat has a positive impact on health. In 2016, researchers investigated a large population study that had followed people for three decades. They found that consuming higher amounts of unsaturated fat was associated with a lower risk of mortality.
According to Harvard School of Health, foods that contain unsaturated fat include:
- avocados and avocado oil
- nuts, such as walnuts, macadamias, almonds, and Brazil nuts
- seeds, such as flax and pumpkin seeds
- oily fish, such as salmon, tuna, anchovies, and sardines
- olives and olive oil
These are all healthful sources of fat for people following the keto diet.
Despite being a source of saturated fat, coconut oil also has some health benefits. A 2018 study showed that coconut oil increased high-density lipoprotein (HDL), or good, cholesterol compared to olive oil and butter. This type of cholesterol can protect against heart disease.
Trans fats
Most trans fats in the Standard American diet come from hydrogenation, which turns oils into solids and prevents them from going rancid. This is how manufacturers used to make margarine.
However, in 2015 the Food and Drug Administration (FDA) banned manufacturers from adding trans fats to food products because they have no health benefits and raise levels of low-density lipoprotein (LDL), or bad, cholesterol in the blood while lowering good cholesterol. This can increase the risk of heart disease.
Previously, manufacturers in the United States added trans fats to many processed foods. According to the Centers for Disease Control and Prevention (CDC), foods included:
- fried foods
- snacks, such as microwave popcorn
- frozen pizzas
- baked goods
- ready-to-use frosting
- coffee creamers
Trans fats do occur naturally in small amounts in animal fats. They have been in the food chain ever since people started domesticating animals for food. There is little evidence that naturally occurring trans fats are harmful.
Some meat products
Many people on a keto diet aim to reach their fat and protein ratios by consuming meat products. However, aside from the potential risks of saturated fat, some meat products have downsides.
According to a 2018 analysis, cooking meats at high temperatures can produce carcinogens, which are compounds linked to cancer. Additionally, processed meats, such as bacon, sausages, and ham, may contain even higher levels of potential carcinogens.
When eating meat on the keto diet, it is best to:
- eat cuts of fresh meat rather than processed meat
- steam, boil, or stew meat rather than grilling or barbecuing
- choose grass-fed meat over grain-fed, as a 2010 study found it contains more omega-3
- eat white meat, such as chicken and turkey
A 2019 study indicated that people who ate 1 serving of beef daily had three times the levels of a chemical linked to heart disease than people who ate lots of white meat or plant-based protein.
Someone starting a keto diet may struggle to eat the required amount of fat. Meal planning can help ensure a person gets enough fat each day.
A person can include more fat in their diet by:
- Adding fats to hot drinks: Someone can add butter or coconut oil to hot drinks such as coffee, matcha, green tea, or hot chocolate.
- Using vegetables as a vehicle: Adding a high fat dressing or dip to low carbohydrate vegetables, such as broccoli, zucchini, or celery, can create a high fat snack or side dish. Salad dressings that contain olive or avocado oil can also add flavor to a low carbohydrate salad.
- Making fat bombs: Fat bombs are ball-shaped snacks that are high in fat and low in carbohydrates. There are lots of recipes for fat bombs online that contain coconut or nut butter as a base. A person can freeze fat bombs and eat them when needed.
- Eating oily fish: Oily fish such as salmon or tuna contains more healthful fats than white fish, such as cod or haddock.
- Choosing fatty cuts of meat: Some cuts of meat contain more fat than others. Eating poultry with the skin left on is a way of increasing a meal’s fat content.
- Eating fatty snacks: Olives, boiled eggs, nuts, and avocados are portable snacks that contain fat. A person can pack these in a bag and eat them on the go.
If someone does not consume enough fat on the keto diet, they may not stay in ketosis.
A 2020 article on the keto diet states that a low carbohydrate diet can positively affect people with:
People with these conditions who are following the keto diet may see improvements in blood glucose levels, insulin sensitivity, and blood pressure. They may also lose weight, which can help someone with obesity reach a moderate weight.
However, the keto diet can have some short term adverse effects. When someone first transitions to the keto diet, they may experience what some people call “keto flu.” A person may experience symptoms such as fatigue, nausea, and dizziness. These symptoms usually resolve in a few days or weeks.
There is not much evidence on the long term impact of the keto diet. However, someone following the keto diet for an extended period may experience:
- vitamin and mineral deficiencies
- kidney stones
- fatty liver disease
- hypoproteinemia, or abnormally low levels of protein in the blood
A keto diet may also lead to an increase in bad cholesterol.
People with type 1 diabetes should not try the keto diet due to the risk of ketoacidosis. Ketoacidosis occurs when excessive ketones produce a dangerous level of acid in the blood.
People with healthy levels of insulin are unlikely to experience ketoacidosis. However, people who do not have diabetes but follow an extremely low carbohydrate diet for an extended period can develop the condition, but this is rare.
The 2020 article advises that people follow a keto diet for a maximum of 6–12 months before gradually transitioning back to a diet that includes more carbohydrates.
Healthful fats for the keto diet include oily fish, olive oil, avocado oil, nuts, nut butters, and seeds. A person following this diet may wish to eat more white meat than red meat and avoid processed meat products.
By planning meals ahead of time and including more healthful fats in snacks, with vegetables, salads, and hot drinks, a person can reach the requirements for ketosis. It is also a good idea to check the nutrition facts panel on food labels.
Because there is not much evidence on the long term effects of the keto diet, researchers recommend transitioning off this diet after 6–12 months.
