1.0 Introduction

“Ketosis is a word you’ll probably see when you’re looking for information on diabetes or weight loss. Is it a good thing or a bad thing? That depends.” (WebMD, 2019).

This article provides an overview of the ketogenic (keto) diet which involves consuming a very low amount of carbohydrates and replacing them with fat to help your body burn fat for energy.

Purported health benefits can include weight loss and lowering your risk for certain diseases. However, as well as the positives there can be negatives. Understanding what a keto diet actually is and involves is important to understand whether or not you intend to follow a keto diet. When considering keto diets, you need to understand several concepts including ketosis (or ketogenesis), ketones, and ketoacidosis.

This article is not intended to be fully comprehensive, merely provide a good overview of the topic, although the links will provide further detail if required.

2.0 Ketosis and Ketones

2.1 Definition of Ketosis

There are a variety of definitions of ketosis (or ketogenesis), although they generally outline the same principle.

Restrict carbohydrate intake > burn fat > produce ketones

“Ketosis is a process that happens when your body doesn’t have enough carbohydrates to burn for energy. Instead, it burns fat and makes things called ketones, which it can use for fuel.” (WebMD, 2019).

“Nutritional ketosis, the aspirational endpoint of ketogenic diets, is achieved by restricting carbohydrate intake, moderating protein consumption, and increasing the number of calories obtained from fat.” (Dowis & Banga, 2021).

“Ketogenesis is a metabolic pathway that produces ketone bodies, which provide an alternative form of energy for the body. The body is constantly producing small amounts of ketone bodies that can make 22 ATP each in normal circumstances, and it is regulated mainly by insulin. In a state of ketosis, ketone body production is increased when there are decreased carbohydrates or increased fatty acids. However, ketoacidosis can occur if too many ketone bodies accumulate, such as in cases of uncontrolled diabetes.” (Dhillon & Gupta, 2023).

Dhillon and Gupta’s 2023 article gives a good outline of the mechanism and biochemistry of ketogenesis (which I will not repeat here).

• Mild ketosis is a natural phenomenon that occurs in humans during fasting and lactation.
• Postexercise ketosis is a well-known phenomenon in mammals.
• Although most of the changes in the physiological parameters induced following exercise revert back to their normal values rapidly, the level of circulating ketone bodies increases for a few hours after muscular activity ceases.
• It has been found that in trained individuals, a low blood ketone level protects against the development of hypoglycaemia during prolonged intermittent exercise.

2.2 What are Ketones?

Simply put, ketones are a type of chemical that your liver produces when it breaks down fats.

Generally, your body will use ketones as an energy source:

• During fasting;
• Long periods of exercise (think marathons and triathlons); and/or
• When you restrict carbohydrate intake.

Given the prevalence of overweight and obesity having less carbohydrates might sound like a good idea, but a build up of ketones in your blood can have undesirable consequences (discussed later). However, you can (generally) have low levels of ketones in your blood without any issues. The amount of ketones you can have without detrimental effects varies between individuals.

2.3 Key Points

• Everyone has ketones, although for those with diabetes it can lead to problems.
• Ketones are chemicals made in your liver.
• You produce ketones when you do not have enough of the hormone insulin in your body to turn sugar (aka glucose) into energy.
• When this happens you need another source, so your body uses fat instead.
• Your liver turns this fat into ketones, a type of acid, and sends them into your bloodstream.
• Your muscles and other tissues can then use ketones for fuel.
• For a person without diabetes, this process does not become an issue.
• However, if you are diabetic, things can run out of control and you build up too many ketones in your blood.
• If the level goes too high, it can become life-threatening.
• Getting the liver to make ketone bodies is tricky:
• It requires that you deprive yourself of carbohydrates, fewer than 20 to 50 grams of carbs per day (keep in mind that a medium-sized banana has about 27 grams of carbs).
• It typically takes a few days to reach a state of ketosis.
• Eating too much protein can interfere with ketosis.

2.4 Testing for Ketones

You can test for ketones in your urine or blood, or on your breath. A urine test may show a different result to a blood/breath test. Your ketone levels are generally measured via one ketone body in the bloodstream, beta hydroxybutyrate (BHB) (Dhatariya, 2017).

• A urine test will tell you what your ketone levels were a few hours ago, and will usually quantify results as
  • No ketones;
  • Trace amounts of ketones;
  • Moderate levels of ketones; or
  • Large amounts of ketones.
• A blood test will tell you your ketone levels in real-time, and will usually quantify results as:
  • Less than 0.6: Normal;
  • 0.6 to 1.0: Slightly high (or ‘light’ nutritional ketosis);
  • 1.0 to 3.0: Moderately high (or ‘optimal’ ketosis); or
  • Higher than 3.0: Very high.
• Measured as 0.0 mmol/l (millimoles per litre) (UK standard) or 0.0 mg/dL (milligrams per 100 millilitres) (US standard).
• A breath test will tell you your ketone levels in real-time, and will usually quantify results similar to a blood test.

Normal value ranges may vary slightly among different laboratories and manufacturers (for example: 0.6 to 1.0 versus 0.6 to 1.5, and 1.0 to 3.0 versus 1.5 to 3.0).

Manufacturers also offer wearable devices (with obligatory app), sometimes known as a continuous ketone monitor (CKM); you can monitor your glucose levels with a continuous glucose monitor (CGM). Devices and kits will generally test/measure your glucose and ketone levels (the latest versions). They are aimed at those with diabetes but many following keto, or other similar, diets are also now using them.

3.0 How Does Your Body Get its Energy?

There are two ways your body gets its energy:

Source	Outline
From the food we eat (including what we drink, except water)	The body will convert the calories from the food we eat into energy: glucose.
From our body fat (energy from food previously consumed but not used)	The body will convert your stored body fat into energy: glucose.

4.0 What is a Keto Diet?

Before we discuss what a keto diet is, we must know what a healthy, balanced diet looks like.

For most people, their diet will consist of carbohydrates (carbs), protein, and fat; but one must also remember the other elements of a healthy, balanced diet (e.g. vitamins and minerals).

4.1 The Principles of a Healthy, Balanced Diet

The Eatwell Guide, found on the UK’s National health Service (NHS) website, provides an overview of such a diet dividing the foods and drinks we consume into five main food groups:

• Fruit and vegetables;
• Potatoes, bread, rice, pasta and other starchy carbohydrates;
• Beans, pulses, fish, eggs, meat and other proteins;
• Dairy and alternatives; and
• Oils and spreads.

With these five main food groups in mind, The Eatwell Guide suggests:

• Fruit and Vegetables:
  • Aim to eat at least 5 portions of a variety of fruit and veg each day.
  • Choose from fresh, frozen, tinned, dried or juiced.
  • Remember that fruit juice and smoothies should be limited to no more than a combined total of 150ml a day.
  • Fruit and vegetables are a good source of vitamins, minerals and fibre.
• Meals:
  • Starchy food should make up just over a third of the food you eat.
  • Choose higher fibre or wholegrain varieties, such as wholewheat pasta and brown rice, or simply leave the skins on potatoes.
  • There are also higher fibre versions of white bread and pasta.
  • Starchy foods are a good source of energy and the main source of a range of nutrients in your diet.
• Proteins:
  • These foods are good sources of protein, vitamins and minerals.
  • Pulses, such as beans, peas and lentils, are good alternatives to meat because they are low in fat and they’re a good source of fibre and protein, too.
  • Choose lean cuts of meat and mince, and eat less red and processed meat like bacon, ham and sausages.
  • Aim for at least 2 portions (2 x 140g) of fish every week, 1 of which should be oily, such as salmon, sardines or mackerel.
• Diary (or diary alternatives):
  • Milk, cheese, yoghurt and fromage frais are good sources of protein and some vitamins, and they are also an important source of calcium, which helps keep your bones healthy.
  • Try to go for lower-fat and lower-sugar products where possible, like semi-skimmed, skimmed or 1% fat milk, reduced-fat cheese or plain low-fat yoghurt.
• Fats:
  • Unsaturated fats are healthier fats and include vegetable, rapeseed, olive and sunflower oils.
  • Remember all types of fat are high in energy and should be eaten in small amounts.
  • Eat foods high in fat, salt and sugar less often and in small amounts:
  • These foods include chocolate, cakes, biscuits, sugary soft drinks, butter, ghee and ice cream.
  • They are not needed in your diet, so should be eaten less often and in smaller amounts.
• Fluid:
  • Drink plenty of fluids – the UK government recommends 6 to 8 cups or glasses a day
  • Water, lower-fat milks, lower-sugar or sugar-free drinks and tea and coffee all count.
  • Fruit juice and smoothies also count towards your fluid consumption, but they contain free sugars that can damage teeth, so limit these drinks to a combined total of 150ml a day.

According to Public Health England’s Government Dietary Recommendations, published in 2016, the average 19-64 should consume the following:

	Energy	Protein	Fat (less than)	Carbohydrate (at least)	Free Sugars (less than)	Salt (less than)	Dietary Fibre
Male	2,500 kcal/day	55.5 g/day	97 g/day	333 g/day	33 g/day	6.0 g/day	30 g/day
Female	2,000 kcal/day	45.0 g/day	78 g/day	267 g/day	27 g/day	6.0 g/day	30 g/day

Notes

• Kcal/day = kilocalories per day.
• g/day = grammes per day

The exact amount of calories you require each day is influenced by a number of factors such as gender, age, and physical activity level (think activities levels for your job as well as any exercise). Males generally need more calories than females, younger and older people need less, and those who exercise need more than those who do not.

4.1.1 Main Differences between Glucose Diet and Keto Diet

The recommended healthy, balanced diet is sometimes referred to in keto circles as the Glucose Diet – as a greater percentage of energy comes from sugars.

Glucose Diet	Keto Diet
Most people’s fuel source	Alternative fuel source
Comes primarily from carbs	Requires and adequate presence of fat
Referred to as the ‘sugar burning’ mode	Referred to as the ‘fat burning’ mode

4.1.2 How Much Fat Do I Need?

• The UK government recommends that total fat makes up no more than 35% total energy consumed.
• Saturates being no more than 11% total energy consumed (approximately 30 g/day for males and 20 g/day for females).
• Because the keto diet has such a high fat requirement, you must eat fat at each meal.
• In a daily 2,000-calorie diet, that might look like 165 grams of fat, 40 grams of carbs, and 75 grams of protein.
• However, the exact ratio depends on your particular needs.
• Some healthy unsaturated fats are allowed on the keto diet, such as nuts (almonds, walnuts), seeds, avocados, tofu, and olive oil.
• Saturated fats from oils (palm, coconut), lard, butter, and cocoa butter are also encouraged in high amounts.

4.1.3 How Much Protein Do I Need?

“Excess protein consumed is usually stored as fat, while the surplus of amino acids is excreted. This can lead to weight gain over time, especially if you consume too many calories while trying to increase your protein intake.” (Healthline).

• Protein recommendations are based on how much one needs per kilogram (kg) of your bodyweight, for adults this is 0.75g per kg of bodyweight.
• Current recommendations are 56g/day for men and 45g/day for women (based on bodyweights of 75kg for men and 60kg for women).
• On average, in the UK, men are eating about 85g and women about 67g of protein a day.
• This would suggest that, on average, we are eating more than the requirements, so it is likely that most of us are getting enough protein.
• Some people, for example athletes or older adults may have higher protein requirements.
• Protein can be animal-based, plant-based, and diary or diary-alternatives.
• A keto diet does not (typically) discriminate between lean protein foods and protein sources high in saturated fat such as beef, pork, and bacon.

4.1.4 How Much Carbohydrate Do I Need?

The are a number of carbohydrates to consider: starchy foods, sugar (including free sugars), and fibre.

Starchy foods are foods that are rich in starch which is a type of carbohydrate (aka carbs).

• This food group includes a variety of types of food such as:
  • Grains like rice, bulgur wheat, oats, barley and rye;
  • Products made from grains like breakfast cereals, and from flour like bread and bread products (including rolls, pitta, focaccia, chapatis, bagels, baguette, ciabatta, pizza base, roti and tortillas) as well as pasta, noodles and couscous;
  • Potatoes and potato products (including baked, boiled and mashed potatoes, oven chips and potato gnocchi); and
  • Yams, cassava and plantain.
    • Other root vegetables like sweet potatoes, parsnips and turnips are starch rich but count as part of the fruit and vegetables food group within the Eatwell Guide as they are more often eaten as vegetables rather than as the main starchy staple.
• Starchy foods/carbs sometimes get a bad press and there may be a worry that they are fattening.
• However, starchy foods can be part of a healthy, balanced diet.
• What is important is the types of starchy foods you eat, sometimes termed ‘carbohydrate quality’.
• For a healthier diet, you should choose more wholegrains and higher fibre foods, such as wholemeal breads, brown rice, wholewheat pasta, oats and other wholegrain breakfast cereals and potatoes with skins.
• Starchy foods are an important source of fibre as well as vitamins and minerals (such as B vitamins, iron, calcium, and folate).
• What happens when you eat starchy foods?
  • When you eat starchy foods, your digestive system breaks the starch they contain down to glucose.
  • The glucose is absorbed into the blood and insulin, the important hormone that regulates your blood sugar, is released and helps the glucose in your blood to enter your cells to use for energy or to store.
  • This helps to keep glucose levels in the blood stable and ensure you have a steady supply of glucose in your body.
  • In people with healthy blood glucose control, blood sugar is kept in a normal range.
  • In diabetes, when the body cannot make enough or any insulin or cannot effectively use the insulin it makes, this system does not work.
  • Different starchy foods increase your blood sugar levels at different speeds.
  • The different speeds can be ranked by the glycaemic index (GI).

Sugar and Free Sugars

• Sugar is a simple carbohydrate.
• Although you may think of ‘sugar’ as one thing, there are actually several types.
• Glucose and fructose joined together make sucrose, which is what you would normally call ‘sugar’, and is used for baking or putting in your tea or coffee.
• Other sugars include lactose (naturally present in milk) and maltose (found in cereal grains).
• Sugars can come in different forms:
  • They can be naturally occurring like in fruit and milk; or
  • They can be added and used as an ingredient in different foods and drinks.
• There is agreement that the type of sugars that we should be eating less of in our diets is ‘free sugars’.
• Free sugars include:
  • All added sugars in foods and drinks. These may be added in by a food manufacturer, a chef or by you at home and include the sugars you would find in biscuits, chocolate, and other sweet foods.
  • Sugars present in honey, syrups (like golden syrup, maple syrup or agave syrup), nectars, fruit juices and fruit juice concentrates.
    • These are ‘free’ because they are not inside the cells of the foods we eat.
    • When fruit is turned into fruit juice, the sugars come out of their cells and become free sugars.
    • The fibre is lost and it is easier to consume extra sugar without realising.
    • For example, you are unlikely to eat four oranges in a row but you might drink their juice in one glass of orange juice without feeling full.
• Naturally occurring sugars:
  • Sugars in diary foods like milk or yoghurt or in fresh, cooked, or dried fruit and vegetables.
• What about juices and smoothies?
  • When fruit and vegetables are juiced the sugars are released from the structure of the food.
  • It has been suggested that sugars such as those in juices and smoothies can be consumed more easily in much greater quantities than sugars present within structures that have not been broken down.
  • In other words, you can drink a glass of juice or smoothie much quicker than the time it would take you to eat the number of whole fruits and vegetables it took to make it, and this could lead to overconsumption of calories and sugars.
• What about ‘hidden sugars’?
  • You may find that sugars are sometimes added to products that you do not think of as ‘sweet’ such as ready-made sauces or salad dressings.
• Free sugars should make up no more than 5% total energy consumed.

Fibre

• Dietary fibre is a term that is used for carbohydrates found naturally in plants that, unlike other carbohydrates (such as sugars and most starches), are not digested in the small intestine and so reach the large intestine (or colon) intact.
• There are many different types of fibre, found in a range of plant foods in the diet.
• Different fibre types can have different effects on your health.
• You may have heard of ‘soluble fibre’ or ‘insoluble fibre’ – these are terms that are sometimes used to describe the types of fibre in your diet.
• Although scientific organisations do not use these terms anymore, as they are not strictly accurate, you may see them being used.
  • ‘Soluble fibre’ is usually used to refer to fibres such as pectins and beta glucans found in foods like fruit and oats; and
  • ‘Insoluble fibre’ is used to refer to fibres found in wholegrains, potatoes with skin and nuts.
• Fibre can also be classified by its:
  • Viscosity (viscous vs. non-viscous); and
  • Fermentability (fermentable vs. non-fermentable).
• Viscous fibres form a gel-like substance that ‘sits’ in the gut.
• This can influence how quickly you absorb certain nutrients like sugar.
• Fermentable fibres can influence the number and type of bacteria in the gut.
• Fibre-containing foods usually have a mix of different fibre types and so the key is to include a variety of plant foods to help you get all the benefits of fibre in your diet.
• Fibre also helps to keep your digestive system healthy and can help to prevent constipation.

4.2 The Principles of a Keto Diet

• Simply put, the keto diet involves consuming a very low amount of carbohydrates and replacing them with fat to help your body burn fat for energy.
• As a very low carb, high fat diet it shares many similarities with the Atkins diet and low carb diets.
• It involves drastically reducing carbohydrate intake and replacing it with fat.
• This reduction in carbs puts your body into a metabolic state called ketosis.
• When this happens, your body becomes incredibly efficient at burning fat for energy.
• It also turns fat into ketones (Section 2.1) in the liver, which can supply energy for the brain.
• Keto diets can cause significant reductions in blood sugar and insulin levels.
• This, along with the increased ketones, has been reported to have some health benefits.
• In addition to helping you burn fat, ketosis can make you feel less hungry.
• It also helps you keep muscle.
• For healthy people, who do not have diabetes and are not pregnant, ketosis usually kicks in after 3 or 4 days of eating fewer than 50 grams of carbohydrates per day.
• You can start ketosis by fasting, too.
• Although all fruits are rich in carbs, you can have certain fruits (usually berries) in small portions.
• Also rich in carbs, vegetables are restricted to leafy greens (such as kale, Swiss chard, spinach), cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, and summer squashes.
• A cup of chopped broccoli has about six carbs.

Type of Diet	Fat	Protein	Carbohydrate
Healthy, Balanced Diet	Not more than 35%	10%	50-55%
Keto Diet	70-90%	20-25%	5-10%

4.2.1 Examples of Keto Diets

• Standard ketogenic diet (SKD):
  • This is a very low carb, moderate protein and high fat diet.
  • It typically contains 70-75% fat, 20% protein, and only 5-10% carbs.
• Therapeutic ketogenic diet (TKD):
  • This is a very low carb, low protein and high fat diet.
  • It typically contains 90% fat, 5% protein, and only 5% carbs.
• Cyclical ketogenic diet (CKD):
  • This diet involves periods of higher carb refeeds, such as 5 ketogenic days followed by 2 high carb days.
• Targeted ketogenic diet (TKD):
  • This diet allows you to add carbs around workouts.
• High protein ketogenic diet:
  • This is similar to a standard ketogenic diet, but includes more protein.
  • The ratio is often 60% fat, 35% protein, and 5% carbs.
• However, only the standard and high protein ketogenic diets have been studied extensively.
• Cyclical or targeted ketogenic diets are more advanced methods and primarily used by bodybuilders or athletes.

4.2.2 Low Carbohydrate Diets

• Low carbohydrate or ‘low-carb’ diets are often talked about for weight loss, especially for people with type 2 diabetes.
• There are lots of different types of low-carb diet and there is no definition of exactly how much carbohydrate you can have on a low-carb diet. Some diets may restrict carbohydrate to less than 45% of your daily calories (this is only a little less than we eat on average) but very low keto diets often mean eating less than 10% of calories from carbohydrate.
• Whatever the type, low-carb diets recommend restricting starchy foods like bread, rice and pasta.
• It is known that for most people with type 2 diabetes, managing their weight is key to managing their condition.
• There is evidence that in people living with type 2 diabetes and with overweight or obesity, in the short-term (up to about 6 months) lower carb diets can be effective in helping some people lose weight and that they may help people with type 2 diabetes to manage their blood sugar.
• However, studies have not found that lower carb diets are better than other diets (such as low-fat diets) in the long-term – different types of diet suit different people and the key is being able to stick with it.
• On very low-carb or ‘keto’ diets you generally cannot include any starchy foods.
• This may be an issue for health in the longer term as this makes it difficult to eat enough fibre, especially as beans, lentils and some fruits and vegetables also tend to be restricted.
• If you are thinking about trying a low-carb diet, learn more by reading these pages from Diabetes UK.

“It is important to clarify that a low-carb diet typically refers to a diet with an intake of 50 to 150 g of carbohydrate per day. However, although this is a lower amount of carbohydrates than the standard American diet, it is not low enough to enter nutritional ketosis. Only when a patient restricts carbohydrates to less than 50 g/day will the body be incapable of fueling the body by glucose and will switch to burning fat” (Dowis & Banga, 2021).

5.0 Signs You Are Transitioning to Ketosis

• Ketones can be detected on the breath (pear-drop smell)
• Increased ketones (detected via urine, blood, or breath test)
• Decreased appetite/hunger
• Increased thirst
• Dry mouth
• Changes in urination (usually more frequent)
• Weight loss
• Increased energy (allegedly)
• Improved physical performance (allegedly)

Modifying your diet and practicing intermittent fasting can help you enter ketosis faster.

Blood, urine, and breath tests are available, which can help determine whether you have entered ketosis by measuring the amount of ketones produced by your body (Section 2.3).

6.0 The Positives and Negatives of a Keto Diet

“Despite the fact that short-term high protein diet could be necessary in several pathological conditions (malnutrition, sarcopenia, etc.), it is evident that “too much of a good thing” in diet could be useless or even harmful for healthy individuals.” (Delimaris, 2013).

6.1 The Positives

• Ketogenic diets have shown promise with (Dowis & Banga, 2021):
  • Losing weight;
  • Reversing the signs of metabolic syndrome;
  • Reducing or eliminating insulin requirements for type 2 diabetes;
  • Reducing inflammation;
  • Improving epigenetic profiles;
  • Altering the microbiome;
  • Improving lipid profiles;
  • Supplementing cancer treatments;
  • Potentially increasing longevity; and
  • Improving brain function.
• “KD [ketogenic diet] has helped patients with diabetes reduce their HbA1c and reduce the need for insulin.” (Dowis & Banga, 2021).
• “There is evidence to suggest that a KD can help with weight loss, visceral adiposity, and appetite control. The evidence also suggests that eating a high-fat diet improves lipid profiles by lowering low-density lipoprotein (LDL), increasing high-density lipoprotein (HDL), and lowering triglycerides (TG).” (Dowis & Banga, 2021).
• “Due to the Warburg effect, the KD is used as an adjuvant treatment to starve cancer cells, making them more vulnerable to chemotherapy and radiation.” (Dowis & Banga, 2021).
• A study of the long-term effects (24-weeks) of a keto diet suggests it “shows the beneficial effects”, significantly reducing body weight, triglycerides, LDL cholesterol, blood glucose, and increased HDL cholesterol; with no “significant side effects in the patients.” (Dashti et al., 2004).

6.2 The Negatives

• If ketone levels build up they can cause the body to become to acidic.
• It is recommended that you keep saturated fats to no more than 7% of your daily calories because of the link to heart disease; the keto diet is associated with an increase in ‘bad’ LDL cholesterol, which is also linked to heart disease (Harvard Health Publishing, 2020).
• Other potential risk include:
  • Nutrient deficiency;
  • Liver problems;
  • Kidney problems;
  • Constipation; and/or
  • Fuzzy thinking and mood swings.
• “Diet which is high in protein generates a large amount of acid in body fluids. The kidneys respond to this dietary acid challenge with net acid excretion, and, concurrently, the skeleton supplies buffer by active resorption of bone resulting in excessive calcium loss. Moreover, acid loading directly inhibits renal calcium reabsorption leading to hypercalciuria in combination with the exorbitant bone loss.” (Delimaris, 2013).
• “Conclusions. The findings of the present study suggest that there is currently no reasonable scientific basis in the literature to recommend protein consumption above the current RDA (high protein diet) for healthy adults due to its potential disease risks. Further research needs to be carried out in this area, including large randomized controlled trials.” (Delimaris, 2013).
• “Higher total protein intake, expressed as percentage of energy, was significantly associated with a greater risk of weight gain when protein replaced carbohydrates (HR: 1.90; 95%CI: 1.05, 3.46) but not when replaced fat (HR: 1.69; 95%CI: 0.94, 3.03). However, no association was found between protein intake and waist circumference. Contrary, higher total protein intake was associated with a greater risk of all-cause death in both carbohydrate and fat substitution models (HR: 1.59; 95%CI: 1.08, 2.35; and HR: 1.66; 95%CI: 1.13, 2.43, respectively). A higher consumption of animal protein was associated with an increased risk of fatal and non-fatal outcomes when protein substituted carbohydrates or fat.” (Hernandez-Alonso et al., 2015).
• High protein diets that restrict carbohydrates are typically lower in fibre, which can lead to constipation.
• Studies vary on hydration. Some note as protein intake increases, hydration levels decrease; although others suggest there is minimal impact on hydration.
• Currently, there is no link between high protein intake and kidney damage in otherwise healthy people, although excess protein can cause damage in those with pre-existing kidney disease. This is because of the excess nitrogen found in the amino acids that make up proteins. Damaged kidneys have to work harder to get rid of the extra nitrogen and waste products of protein metabolism.
• Studies have shown that certain high-protein diets that are particularly high in red meat-based protein are linked to an increased risk of various health issues, including cancer. In contrast, eating protein from other sources has been associated with a decreased risk of cancer. 
• Diets that are high in protein and meat may cause calcium loss. This is sometimes associated with osteoporosis and poor bone health.
• You could suffer from bad breath. This could be in part because your body goes into ketosis (discussed earlier), which produces chemicals that give off an unpleasant fruity smell.

6.3 Types of Ketoacidosis

There three clinically relevant types of ketoacidosis to consider (Ghimire & Dhamoon, 2023):

• Diabetic ketoacidosis (DKA);
• Alcoholic ketoacidosis (AKA); and
• Starvation ketoacidosis (SKA).

Ghimire and Dhamoon’s 2023 article provides a good outline of ketoacidosis (which I will not repeat here).

6.3.1 Diabetic Ketoacidosis

• High levels of ketones in your blood is a sign that something maybe wrong.
• You can tell if you have high levels of ketones in your blood by checking for them.
• A medical professional can give you an idea of what your target range is and what to do if you go above it.
• If you treat your diabetes with insulin, your body should be using the insulin you give it to change blood sugar into energy.
• Howver, if you do not have enough insulin, your body will start to use fat for energy.
• When you use fat for energy your liver starts to produce ketones (Section 2.1).
• When ketones build-up in the blood, they can become acidic and lead to DKA, considered a medical emergency.
• DKA can be life-threatening, so you need to know what the symptoms, how to check for them, and how to get treatment straight away.
• If you have type 1 diabetes, you are more at risk of experiencing DKA than those with other types of diabetes.
• If you have type 2 diabetes and use insulin then you should still look out for the signs of DKA.
• DKA is also common in those who have not yet been diagnosed with type 1 diabetes, especially children.

6.3.2 Can Following a Keto Diet Cause DKA?

• Following a keto diet does not necessarily cause DKA.
• A keto diet leads to ketosis when your body breaks down stored fat to convert it into energy.
• You might think that with more ketones in your blood this would increase your risk of DKA.
• However, this ketosis does not lead to DKA if your pancreas is still producing insulin, or you inject the right amount of insulin for your diabetes, and your blood does not become acidic.
• But, if you are considering a ketogenic diet you should speak to a medical professional first.
• With DKA, the blood becomes acidic when ketones build up and blood glucose levels are usually high because there is no insulin.

6.3.3 Alcoholic Ketoacidosis

Alcoholic ketoacidosis occurs in patients with chronic alcohol abuse, liver disease, and acute alcohol ingestion.

6.3.4 Starvation Ketoacidosis

Starvation ketoacidosis occurs after the body is deprived of glucose as its primary source of energy for a prolonged time, causing fatty acids to replace glucose as the major metabolic fuel.

7.0 Useful Stuff

• UK NHS The Eatwell Guide.
• UK NHS Eating a Balance Diet.
• Public Health England: Government Dietary Recommendations (2016).
• Diabetes UK: Ketones and Diabetes.