The Basics of Keto Diet & Its Risks

What is a keto diet?

A keto diet sharply reduces carbohydrate intake, provides moderate protein and gets most energy from fat. It aims to promote nutritional ketosis, a metabolic state in which the body uses ketones as an alternative energy source. Unlike a general low-carbohydrate diet, which may allow more carbohydrates, a ketogenic diet restricts carbohydrates sufficiently to promote ketosis. ^{[1, 8]}

The exact proportions of carbohydrates, protein and fat can vary. Many weight-management keto plans limit carbohydrate intake to approximately 20–50 g per day, although individual requirements may differ. ^{[1, 2, 10]}

How does nutritional ketosis work?

Carbohydrates from food are normally an important source of glucose, which the body uses for energy. When carbohydrate intake falls substantially, the liver increases production of ketone bodies from fat. These ketones can be used as an alternative fuel by many tissues, including the brain. The body also continues to make some glucose through gluconeogenesis for tissues that need it. ^[1]

During nutritional ketosis, ketone levels increase while blood acidity remains normal. This differs from diabetic ketoacidosis (DKA), a serious medical emergency in which excessive ketone production causes the blood to become too acidic, usually due to insufficient insulin. ^{[1, 9]}

Can a keto diet help with weight loss?

It can for some people. Ketogenic and very-low-carbohydrate diets may help reduce appetite and support weight loss, particularly in the short term. ^{[2, 6, 15]} Some of the initial weight loss comes from water as stored glycogen is depleted. ^[17] Over time, weight-management results also depend on overall energy intake, diet quality, nutritional adequacy and whether the eating pattern can be maintained. ^{[2, 12, 17]}

A keto diet is therefore one possible weight-management approach rather than a guaranteed or uniquely superior solution. A less restrictive eating pattern may be easier for some people to maintain while still supporting a healthy weight. ^{[2, 12, 17]}

What foods are commonly eaten on a keto diet?

Typical keto meals include a variety of lower-carbohydrate foods and fat sources. Common choices include: ^{[8, 12]}

• Fish, seafood, eggs, poultry and unprocessed meat
• Unsaturated-fat sources such as olive oil, avocado, nuts, seeds and olives
• Lower-carbohydrate vegetables such as leafy greens, broccoli, cauliflower and courgette
• Lower-carbohydrate dairy foods, such as certain cheeses, depending on individual needs
• Small portions of fruits such as berries

For heart health, fat quality matters. Choosing more unsaturated fats and fewer foods high in saturated fat is more consistent with current cardiovascular dietary guidance. ^[11]

What are the common side effects of a keto diet?

During the first days or weeks, some people may experience temporary side effects, sometimes called the “keto flu”. These may include: ^{[1, 8, 14]}

• Headache, tiredness or dizziness
• Nausea or stomach discomfort
• Constipation
• Muscle cramps
• Temporary sleep disturbance

These symptoms are not necessarily a sign that the body is “detoxing”. They may be related to changes in fluid and electrolyte balance as the body adapts to the diet, while reduced fibre intake may contribute to constipation. ^{[1, 8, 14]}

What are the longer-term risks and other safety concerns?

A strict keto diet may make it harder to obtain enough fibre, vitamins and minerals, particularly if food choices are limited. Some people may experience constipation or increased LDL cholesterol, depending on their diet and individual response. ^{[8, 10, 11, 14]} Kidney stones have also been reported, particularly among people following long-term therapeutic ketogenic diets. ^{[13, 14]} Evidence on the long-term safety of ketogenic diets for weight management, especially beyond two years, remains limited. ^[17]

Can a keto diet cause ketoacidosis?

A keto diet generally produces nutritional ketosis, which is different from diabetic ketoacidosis (DKA). During nutritional ketosis, ketone levels rise while blood acidity remains normal. In contrast, DKA is a medical emergency involving excessive ketone accumulation and increased blood acidity, usually due to insufficient insulin. ^{[1, 9]}

Can people with diabetes follow a keto diet?

Some people with type 2 diabetes may experience improved blood glucose control with carbohydrate restriction, particularly in the short term. However, a strict keto diet is not suitable for everyone. Insulin and certain diabetes medicines, such as sulfonylureas, can increase the risk of hypoglycaemia when carbohydrate intake is substantially reduced. People taking SGLT2 inhibitors should avoid ketogenic diets because of the risk of ketoacidosis. Medication changes should only be made with guidance from a doctor or diabetes care team. ^{[10, 16]}

People with type 1 diabetes require insulin treatment and should never replace prescribed insulin with a ketogenic diet. Anyone with diabetes considering a very-low-carbohydrate diet should discuss the plan with their healthcare professional first. ^[10]

Who should avoid a strict keto diet or seek medical advice first?

A very-low-carbohydrate ketogenic diet is not suitable for everyone. Current diabetes guidance does not recommend very-low-carbohydrate eating plans during pregnancy or breastfeeding, for children, people with kidney disease, or people with or at risk for disordered eating. People taking SGLT2 inhibitors should avoid ketogenic eating patterns because of ketoacidosis risk. ^[10]

Specialist advice is also important for people with a history of pancreatitis or kidney stones, or significant liver disease. These precautions should be distinguished from medically prescribed ketogenic therapy, such as for drug-resistant epilepsy, which requires specialist supervision. ^{[1, 14]}

If you want to try keto, how can you reduce the risks?

• Seek professional advice before starting.
  This is especially important if you have diabetes, take regular medicines or have existing medical conditions. A doctor can assess medical suitability, while a dietitian can advise on nutritional needs and a pharmacist can review medication-related risks. ^{[10, 14]}
• Do not stop or reduce prescribed medicines on your own.
  Medication adjustments should be made under appropriate medical supervision. ^{[10, 16]}
• Prioritise unsaturated fats.
  Choose foods such as olive oil, nuts, seeds and avocado rather than relying heavily on butter, processed meats or coconut oil. ^[11]
• Include fibre-rich, lower-carbohydrate foods.
  Include low-carbohydrate vegetables, nuts and seeds to support fibre and micronutrient intake. ^{[10, 11]}
• Stay adequately hydrated and watch for warning signs.
  Seek medical attention if you experience persistent vomiting, severe weakness, confusion or rapid breathing, particularly if you have diabetes or take SGLT2 inhibitors. ^{[10, 14]}

Takeaway: keto can work for some people, but it is not risk-free

A keto diet may support short-term weight loss, but it is restrictive and may not be suitable for everyone. ^{[2, 12]} A sustainable eating pattern should meet your nutritional needs, support long-term health and take any existing medical conditions or medication-related risks into account. ^{[10, 11, 12, 17]}

If you are considering keto for weight loss or blood sugar management, speak with a qualified healthcare professional. A CARiNG pharmacist can help you review your medicines, identify possible safety concerns and advise when medical or dietitian input is needed.

Frequently asked questions about the keto diet

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