Is Keto Your Match?

Few diets divide opinion like keto. Some people say it changed their lives, giving them steady energy, a clear head and the weight loss they'd struggled for years to achieve. Others felt dreadful on it and gave up within a week. Both can be true, because the real question isn't whether keto works. It's whether keto works for you.

What is a ketogenic diet?

A ketogenic diet is very low in carbohydrates, usually under 50 g a day and often nearer 20 g, moderate in protein and high in fat. With so little carbohydrate available, the body runs short of glucose, its usual fuel. The liver begins turning fat into ketones, an alternative fuel that the brain, heart and muscles can all use. This state is called ketosis.

It's a state our bodies evolved for. For most of human history, food came and went with the seasons and the success of the hunt, and the ability to run on stored fat during lean times was essential for survival.

A medical diet first

Long before keto was a weight-loss trend, it was a medicine. Doctors had noticed for centuries that fasting could calm seizures. In 1921, Dr Russell Wilder at the Mayo Clinic designed a diet that copied the effects of fasting, and named it the ketogenic diet.¹

A century later, it's still used in hospitals, including on the NHS, for children and adults with epilepsy that doesn't respond to medicines. It remains one of the clearest examples of food as medicine.

More than a fuel

Scientists have discovered that ketones do far more than provide energy. The main ketone, beta-hydroxybutyrate, also acts as a signal inside the body:

• It can switch off part of the immune system that drives inflammation, known as the NLRP3 inflammasome.²
• It can switch on genes that protect cells against oxidative stress.³ (See Not Written in Stone.)
• It provides a clean, efficient fuel for the brain, which may be why many people report sharper focus once they've adapted.

Keto isn't a miracle or a menace. It's a powerful tool, and like any tool, it suits some jobs, and some people, better than others.

What keto can do: the evidence

Keto is now being studied for a remarkable range of conditions. The strength of the evidence varies, so here it is in three levels.

Strong and established

• Drug-resistant epilepsy. In trials in children whose seizures didn't respond to medicines, up to around half became seizure-free on a classic ketogenic diet, and up to 85% had fewer seizures.⁴ It's used in specialist NHS clinics for both children and adults.
• GLUT1 deficiency syndrome. In this rare genetic condition, the brain can't take in enough glucose. Ketones can enter the brain by a different route, so the ketogenic diet is the standard, first-choice treatment, feeding a brain that would otherwise be starved of fuel.⁵
• Type 2 diabetes and blood sugar control. The American Diabetes Association has concluded that reducing overall carbohydrate has the most evidence of any eating approach for improving blood sugar.⁶ In a US programme of people with type 2 diabetes following a supervised ketogenic diet, 94% of those using insulin were able to reduce or stop it within a year,⁷ and many of the improvements were still there after two years.⁸ (See Balancing the Sugar Seesaw.)

Good and growing

• Heart and metabolic markers. Across trials, ketogenic diets consistently lower triglycerides and raise "good" HDL cholesterol, though LDL cholesterol can rise in some people.⁹
• Fatty liver. Non-alcoholic fatty liver disease is one of the most common liver conditions in the UK. In one study, cutting carbohydrates brought rapid falls in liver fat within two weeks.¹⁰
• Weight loss. Many people find keto curbs their appetite, and a review of trials found it led to slightly more weight loss than low-fat diets over a year or more.⁹ Even so, in a large trial people did about equally well on a healthy low-carb or a healthy low-fat diet.¹¹ The best diet for weight loss is often the one you can stick to.
• Polycystic ovary syndrome (PCOS), which is closely linked with insulin resistance. In a pilot study, women following a ketogenic diet for six months lost weight and saw improvements in their hormones.¹² (See The Hormone Web.)

Promising early research

• Migraine. Short periods of ketosis have reduced the frequency of migraine attacks in early studies.¹³
• Alzheimer's disease. The ageing brain often struggles to use glucose, but can still use ketones. In a small trial, people with Alzheimer's improved in daily functioning and quality of life on a modified ketogenic diet.¹⁴
• Parkinson's disease. In a pilot trial, a ketogenic diet improved non-movement symptoms such as tiredness and mood more than a low-fat diet.¹⁵
• Mental health. In a Stanford pilot study, people with bipolar disorder or schizophrenia who followed a ketogenic diet saw improvements in both their psychiatric symptoms and their metabolic health.¹⁶ This new field is sometimes called "metabolic psychiatry".

For several of these conditions, the studies are small and more research is needed. Keto should always be used alongside medical care, never instead of it.

Why it suits some people and not others

That year-long weight-loss trial asked a fascinating question: could tests predict who would do best on low-carb and who on low-fat? Researchers tested people's genes and how much insulin they produced. Neither predicted who would succeed.¹¹ Our responses to food are more individual, and more complex, than any single test can capture.

Here are some of the ways people differ:

• Blood fats. In some people, keto improves cholesterol and triglycerides. In others, particularly some lean, active people, LDL cholesterol can rise sharply. A blood test before and after starting is wise.
• Gut bacteria. Keto diets are often low in fibre, and studies show they can reduce helpful bacteria such as bifidobacteria.¹⁷ Without plenty of vegetables, nuts and seeds, the gut can suffer. (See The Master Regulator.)
• Hormones. Some women find very low carbohydrate diets affect their cycle, sleep or mood, and in some people, levels of active thyroid hormone can fall.
• Activity. Endurance athletes can adapt to burning fat, but high-intensity performance may suffer. In elite race walkers, a high-fat diet made their movement less efficient and cancelled out the benefits of their training.¹⁸
• Constitution. In traditional energetic terms, a rich, heavy, oily diet may steady a light, dry, anxious constitution, but weigh down one that's already heavy and sluggish. (See The Architecture of Balance.)

Doing keto well

If keto suits you, the quality of what you eat matters enormously. A diet of processed meat, cheese and cream is a world away from one built on whole foods: (See Meat, Reconsidered.)

• Fill half your plate with non-starchy vegetables: leafy greens, broccoli, cauliflower, courgettes, peppers and mushrooms, for fibre and plant compounds.
• Choose healthy fats: extra virgin olive oil, avocados, nuts, seeds and oily fish.
• Pick quality protein: eggs, fish and good-quality, ideally organic, meat, and go easy on processed meats.
• Keto can be plant-based too. Tofu and tempeh, nuts and seeds, avocado, coconut, olives, mushrooms and plenty of low-carb vegetables can make a nourishing vegan or vegetarian keto diet, though it takes more planning to get enough protein.
• Keep up your minerals. In the first week, many people get "keto flu": headaches, tiredness and cramps, often from losing sodium, potassium and magnesium. Salting food, drinking broth and eating leafy greens helps.
• Consider a gentler path. A lower-carb Mediterranean diet, or cycling in and out of ketosis, can bring many of the benefits with less strain.
• Test, don't guess. Blood tests for sugar, cholesterol, kidney function and thyroid before and after starting show how your own body is responding.

At Rootwise, there's no one-size-fits-all diet. We look at your health, your history, your test results and your constitution to find the way of eating that truly suits you, whether that's keto or something quite different.