🥙 Nutrition

The Keto Diet: What Is It, How Does It Work, And Is It For You?

UPDATED ON Jun 21, 2022

In this article, I’ll be looking at one of the most popular nutrition plans in today’s health and fitness scene: the ketogenic diet. I’ll run through what it is and whether or not you should give it a go.

The basics of Keto – what is it?

The ketogenic diet is a very low carbohydrate diet in which the majority of your calories come from fats and, to a lesser degree, proteins. In this regard it has been compared to the Atkins diet and other low-carb diets, though there are some specific variations and subtle differences that I’ll be going into below.

Embarking on the keto diet will therefore mean drastically cutting back on your carbohydrate intake- especially the easily digested ones like sugar, pasta, white bread and so on which are known to cause large insulin spikes- and replacing it with lots of fat. Your body will then go into the metabolic state known as ketosis, which is the main goal of the keto diet.

When your body is in ketosis, it becomes very efficient at creating energy by burning off your excess fat stores. Though it is often correctly reported that brain activity is heavily reliant on carbohydrates for energy, during ketosis your body will convert fat into ketones in the liver, which are a great energy supply for your brain.

Obviously, using excess fat for energy will bring about a drastic weight loss as all your subcutaneous fat- and much of your visceral fat- is burned through. Alongside this, the keto diet removes the kinds of insulin spikes that are common with eating large quantities of carbohydrates, especially simpler forms, meaning that blood sugar and insulin levels will be stabilised and greatly reduced.

The keto diet: a brief history

The keto diet’s conception had nothing at all to do with weight loss, though this is how it’s most often used today. Originally, it was developed by a team of paediatricians for the treatment of epilepsy in children. It was widely used in this capacity throughout the 1920s and 1930s, though the development of anti-convulsant medicines soon caused its popularity to diminish.

Scientific interest in the keto diet took off once more towards the end of the 1990s when a top Hollywood producer began to promote it. His son was undergoing a version of the keto diet as part of a treatment plan for severe epilepsy, and he created the Charlie Foundation to promote it, sponsoring research and public outreach surrounding it.

In more recent years, its use in the health and fitness industry has become pronounced as people turn away from carbs, looking for healthy ways to keep their energy levels stabilised and their weight down through increased reliance on fat and protein.

Different types of keto diet

Keto is not just keto. There are several versions of the ketogenic diet, including:

  • The standard ketogenic diet (SKD): This is the main one I’ll be referencing. It generally contains around 75% fat, 20% protein and only 5% carbohydrates.
  • The targeted ketogenic diet (TKD): This version of the diet allows you to include extra carbs around workouts to help you power through your training sessions.
  • The high-protein ketogenic diet: This is my favourite version of the keto, playing nicely into gym-goers’ goals when seeking out boosted hypertrophy. As the name suggests, it includes more protein than a standard keto diet, with up to 35% of calories coming from lean sources.
  • The cyclical ketogenic diet (CKD): This is similar to intermittent fasting (IM) in that it schedules your dietary intake quite closely. You will benefit from higher carbohydrate refeeds scattered through your week. A standard routine would be something like five days of ketosis followed by two days of increased carb allowance. This is perfect for anybody new to the keto diet, anybody struggling with the demands of the SKD, or any athletes looking to put in a couple of intensive training sessions into their week.

How the keto diet may help you to lose weight

Keto word with clock fork and measuring tape around, intermittent fasting on keto concept

First and foremost, the keto diet is used these days by people looking to lose weight.

You will lose a fair amount in the first week or so of adopting the keto diet, though few of these lost kilograms will be from fat. When you cut down on carbs, your body sheds the carbs stored in the liver which hold on to water. Water weight therefore drops. Aside from this, there is no room on the keto diet for the sorts of high carb, high sodium processed foods that are an increasingly common staple of modern life. These kinds of foods typically lead to water retention, so eliminating them will naturally lead to less water weight.

Next up, you’ll notice a sense of stability entering into your eating patterns, with hunger playing a much-reduced role. Energy levels will become more consistent and sudden hunger onset will disappear. This is because the refined, simple carbs you may have been eating before will be gone: this will cut out the insulin spiking sugar highs. When your body produces excess insulin, this insulin wants something (food) to grab onto, so your body naturally wants to eat more to level it out. Without this excess insulin, these hunger pangs go away. This alone will help you to lose weight drastically, as you will be naturally and comfortably eating less.

In the absence of ready carbs for energy, your body will then turn to body fat for energy, as mentioned above. Rather than constantly cycling through calories in and calories out to keep yourself going, you will work through your existing reserves. You’ll quickly see a drop on the scales as your body fat fulfils one of its primary natural functions: as caloric lender of last resort, it burns itself to keep you going through a self-imposed lean period.

Finally, it’s worth noting how easy it is to overeat on the kinds of carbs with which the keto diet dispenses. A couple of helpings of biscuits, chocolates, fizzy drinks and sweets throughout the day- the kinds of ‘hidden calories’ that many of us take in without really registering it- will soon add up to several hundred calories and put you into a caloric surplus. This is how many people get into bother with their weight in the first place, without quite knowing why.

I invite you to try over-eating lean chicken breast, avocado and coconut oil- it’s a lot harder to do than bingeing on cake!

It should be noted at this stage that the jury is out with regards scientific consensus on the ketogenic diet’s efficacy and longer-term health benefits. The results are mixed, with some studies showing promising data to back up the keto diet and its practitioners’ claims and others providing contradictory evidence. Realistically, this is one area where it’s a good idea to try for yourself and see how your body responds.

Who is the keto diet good for?

From personal experience, there are a few people for whom the keto diet is a bit of a godsend. First and foremost, if you are pre-diabetic and/or have any kind of insulin sensitivity, any kind of low glycaemic index (GI), low carb diet deserves serious consideration. As mentioned above, a diet like this will help to stabilise blood sugar levels and reduce insulin spikes. As well as aiding in weight loss, which will be a common problem for people with these symptoms, a diet like this will likely reverse conditions like prediabetes and prevent you from developing full-blown diabetes. I have first-hand experience here- I’ve run several clients and even family members on insulin-controlled nutrition programs like the keto diet, with each and every one of them reversing their conditions and losing a lot of weight.

Low carb plans like the keto diet will also be good for anybody who has an underactive lifestyle. If you’re a peasant farmer, on your feet for sixteen hours every day, ploughing fields and herding livestock, then you need carbs. You won’t be able to function without thousands of calories, and these will need to come in cheap, plentiful supply- enter bread and rice. On the other hand, if you’re an office worker who hits the gym a couple of times per week… less so. You don’t need anything like the kind of carb intake with which modern life provides us. Low carb diets with periods of ketosis will be manageable and healthy for you.

Finally, if you’re carb intolerant, or if you have the kind of metabolism that doesn’t need carbs in any great demand, the keto diet will be good for you. You’ll likely lose weight whilst also finding a ridiculous amount of energy that you never knew you had.

Of course, you don’t need to fit these categories to benefit from the keto diet. I invite anybody to try a low-carb diet, whatever your goals. It could do very little for you, or it could change your life- there’s only one way to find out!

The effects of the keto diet on your mind and body

There is nothing new about ketosis: it’s a normal physiological process, originally of use to hunter-gatherers as a backstop for energy when times were lean. Whilst I’ll go into some of the ketogenic diet’s downsides below, there is nothing inherently special or dangerous about ketosis, despite what has been reported at times.

But what are the effects on your body of deliberately maintaining an often-prolonged state of ketosis?

First and foremost, digestive issues will be a big deal, especially at the beginning. In cutting out carbs in such a sweeping manner, you’re also cutting out fibre, which is essential to healthy digestion. You will most likely either be quite badly constipated and bloated for a brief period whilst your body adapts, or else you may find yourself suffering with IBS, diarrhoea or something similar.

The lack of carbohydrates will also put you into something of a withdrawal. You can expect a fair amount of dizziness as your brain adjusts to not having a steady supply of sugar to run on. Moods may fluctuate, with increased irritability and a feeling of fatigue being a particular issue. Shedding the kind of water weight that I mentioned above will keep you dehydrated, and nausea is not uncommon.

These all sound pretty horrific, but don’t worry. If you persist, they should all mostly subside quite quickly. A few weeks of discomfort should be all it takes to adjust.

One issue that will persist, however, is a touch of halitosis that will remain throughout ketosis. The ketone acetone will be very prominent in your breath and it doesn’t smell the nicest.

Of course, some of these will affect your training if you’re a gym goer or an athlete. To begin with, decreased energy levels and dehydration will hamper your performance and rate of recovery. The perception of fatigue, alongside the nausea and depressed mood, will not give you the best mindset for training: just motivating yourself to get out of the house can be hard.

Once more, however, don’t despair. Though the duration and severity of each of these symptoms is highly individualistic, the ones that will hamper you the most are short-term and temporary, disappearing after anything between 4-6 weeks. Once they go, most dieters report an incredible surge in energy, allowing them to push themselves harder than ever before. The increased protein intake will aid your recovery, and the lack of water weight will ultimately make you feel far more athletic.

Calculating what you’ll be eating for ketosis

Ketogenic diet with nutrition diagram written on a note.

In order to do the keto diet correctly, you will need to work out the amounts of fat, protein and carbohydrates your body will need in order both to function and to hit ketosis. You will need to know your basal metabolic rate (BMR) for this, which you can calculate quite simply using an online BMR calculator.

Once you know your BMR, you will be ready to reverse engineer your macronutrient needs from it.

Let’s take my own needs as an example. I weigh 95kg (210lbs) and am very active, which means that I need to eat roughly 3,581 calories per day to maintain my current weight. This is my maintenance intake. If I’m looking to put on weight, I will need to eat more than this (roughly 500 calories more per day to put on 0.5kg/1lb per week) and if I’m looking to lose weight, I will need to eat less (roughly 500 calories per day less to lose 0.5kg/1lb per week.)

But how do I use these numbers to work out my macronutrient needs for ketosis?

Your macro needs for ketosis

Sticking to my own numbers, and assuming that I want to maintain my current weight, it’s quite easy to determine how I would be breaking down my macros on the keto diet.

I need 3,581 calories per day. The keto diet suggests a split of 75/20/5 for fat/protein/carbs: I want 75% of my calories to come from fats, 20% from protein, and only 5% from carbs. In caloric terms, this means that every day I want roughly:

  • 3,581×0.75= 2,686 calories from fat
  • 3,581×0.2= 716 calories from protein
  • 3,581×0.05= 179 calories from carbs

A single gram of fat contains 9 calories. Each gram of protein and carbohydrate contains four calories. In terms of volume for each, I want my daily nutrition plan to amount to roughly:

  • 2,686/9= 298g of fat
  • 716/4= 180g of protein
  • 179/4= 45 of carbs

These are the macros I’ll need to function at full capacity, to maintain my current weight, providing my body with adequate energy, and to remain in a state of near-permanent ketosis. It’s tough: 45g of carbs is minuscule and will be used up quickly and entirely by vegetables. 298g of fat is also hard to hit: taking in such a large volume is rather a daunting task. These numbers really are not built to be easy.

However, if you stock your diet with the correct foods (see below) and prepare your meals intelligently, then you can simply play the numbers to hit ketosis.

Common keto-friendly foods

Keto diet concept. Balanced low-carb food background. Vegetables, fish, meat, cheese, nuts on a dark background.

Animal products feature quite prominently on the ketogenic diet. A common keto diet will be heavy on meat, poultry and seafood. Fatty fish like salmon and sardines are a favourite. All of these are comprised almost exclusively of fat and complete proteins.

Similarly, a keto diet will point you towards non-meat animal products like eggs, cheese, cream, butter, full-fat yoghurt and so forth. Once more, these all contain a mixture of fats and complete proteins.

A keto dieter will also draw heavily on oily plant produce. Nuts, seeds and avocados will deliver plenty of healthy fat. Low carb vegetables can be included in limited amounts: greens, onions, peppers, tomatoes and garlic are all good sources. These will form the bulk of the minimal carbohydrates taken in.

Finally, you would want to look at different oils both for cooking and dressing. Olive oil is common, as are various nut oils. From the point of view of flavour, I would personally recommend relying on coconut oil.

What is off limits?

Basically, anything that’s heavy on the carbs. Foremost, no keto diet will ever have the room for bread or grains, starchy vegetables like white potatoes and corn, simple sugar in any form, or bulk wheat products like pasta or couscous. If you’re on the keto diet, you will not be eating these.

Beans and legumes, though a healthy source of fibre and protein, will be out. For all their micronutrient goodness, most fruits will be a no-go. There are simply too many carbs in them. Processed foods will generally need to be dispensed with.

Finally, alcohol is off limits. It’s pure sugar with no nutritional benefit- essentially wasted calories. On top of this, it will actively slow down your metabolism, so should be amongst the first things you cut out if you decide to go keto.

Keto: a day in the life

So, what does a typical daily meal plan look like for those on the keto diet? I’ve taken the liberty of putting together a sample meal plan. Whilst portion sizes will vary according to your own lifestyle, and your particular metabolic demands (see above), you can see here the kinds of food combinations that will be commonly put together for a relatively healthy keto diet plan.

BreakfastMid-morning snackLunchAfternoon snackDinner
Half an avocadoHandful of salted peanutsChicken breastToasted sunflower and pumpkin seedsFrittata with onions
One grilled tomatoCoffee with creamSpinach wilted in butterCoffee with coconut oilSide salad of grilled halloumi, lettuce, chilli-peppers and walnuts, with an extra-virgin olive oil dressing
Smoked salmonSour cream
Walnut oil dressingFlaked almonds

So, as you can see, you’ll be getting plenty of fat and protein, with minimal carbs (and no carbs from simple or bountiful sources.) It’s also quite an appetising sounding menu, with tasty recipes and a fair degree of variety.

Pros and cons of the Keto diet

Of course, no high-profile diet passes by without its detractors: the keto diet is no different. It is a particularly divisive diet, in fact, with followers often proselytising its many benefits as though it were a veritable panacea, and with opponents labelling it dangerous and foolish. I sit somewhere in the middle, personally, so I’ve taken the liberty of putting together a list of pros and cons to present a relatively impartial view.

Pros of the keto diet

  • Fat loss: in the absence of energy from carbs, your body will burn through your body’s fat reserves instead. As we’re in the midst of a historically unprecedented obesity epidemic, any tool in our fat-fighting arsenal is welcome.
  • Your body doesn’t need many carbs: we all over-eat on carbs. With increasingly sedentary lifestyles, the majority of us just don’t need the kind of massive energy dump given to us by carb heavy diets.
  • It may help to combat cancer: there is very tentative, exploratory work being done which suggests that a very low carb diet may aid in cancer prevention. Any conclusive results are a long way off, however.
  • Your waist will shrink: a large proportion of the fat loss you will experience on the keto diet will come from your abdominal cavity. In turn, this will reduce risk signifiers of diseases like diabetes.
  • Triglycerides will drop: triglycerides circulate in your bloodstream. This is bad news, as they are fat molecules known to bring about a higher risk of heart disease. Dropping them will decrease your risk of heart disease.
  • Increase HDL ‘good’ cholesterol: the higher your HDL cholesterol relative to your LDL ‘bad’ cholesterol levels, the lower your risk of heart disease.

Cons of the keto diet

  • Going carb light isn’t always good: carbs have been getting bad press in recent years, mostly due to the high amount of simple, processed carbs that have characterised many modern, western diets. However, we do need them, especially low glycaemic index (GI) forms. Anybody needing energy to complete a physically demanding job or fitness routine cannot go for long without them.
  • We also need sugar: our bodies need a little sugar in order to function. It helps your brain to work correctly, and a deficit of glucose in your blood stream can lead to…
  • Brain fog: your brain literally feels as though it is shutting down when the sugars are cut off. Or…
  • The keto flu: many people report feeling physically ill when they enter into ketosis. Though this should abate, it sometimes doesn’t, and is incredibly disruptive in the meantime.
  • Diarrhoea: many people often report this unfortunate side effect when entering ketosis. There are several theories as to why it might be the case, though they ‘why’ might be of little consolation when you’re running to the bathroom for the fifth or sixth time that day.
  • Your weight may yo-yo: such a restrictive nutrition plan as the keto diet is inadvisable for most people to follow long term. Most people use it periodically, as part of a 30-90 day cut or cycle. You will likely lose weight during this cycle. However, when people stop, they have a tendency to put all the weight back on, entering into an unhealthy yo-yo effect that is bad for the metabolism and will often be accompanied by muscle wastage.
  • It could be bad for your heart: as so much of the recommended food on the keto diet is high in saturated fat, it can increase overall cholesterol as easily as balancing it out. This leads to an increased risk of heart disease.

My final thoughts on the keto diet

As with most things, the keto diet is a tool that can be wielded expertly to great effect or used poorly to garner poor results. If you know what you’re doing (which, if you’ve read to the end of this article, you hopefully do!) and are clear in your aims, with the willpower to back it up, there is no reason that the keto diet shouldn’t work for you. If you’re carb intolerant, you may actively flourish on the keto diet.

However, I don’t like it in its extremity. My position is always one of caution with carb intake. As a society, we have fewer and fewer physical demands on our energy as our lifestyles become more generally sedentary. Therefore, we don’t need the kinds of high carbohydrate intakes that our forefathers did. This being said, cutting out carbs almost completely is unwise and often unhealthy (see my list of cons above.)

My perfect weight-loss diet would go light on carbs- perhaps 100-150g per day for most people. This is what I’ve used with myriad clients to great effect. This amount is still far less than most people usually eat, but it gives you room for flexibility, room to provide your brain with the sugars it needs, and room to get some much needed fibre into your diet.

Also, extreme diets often fall down before they begin. If I tell you not to think of an elephant, what is the first thing you think about? An elephant. If I restrict your food intake and make a massive song and dance about it, you’ll begin to obsess over food. This is mentally unhealthy and will likely lead to unhealthy eating patterns. It may be worth trying a more sedate, forgiving diet for less drastic yet more long-term success.

If it works for you, the keto diet is great. But if it doesn’t, don’t sweat it. You can still learn a lot from it. Add a slice of toast to your breakfast, rice to your lunch and a piece of fruit to your afternoon snack and the above daily menu example will be incredibly healthy. You won’t be in ketosis, but your body will be getting what it needs and no more: you will still most likely lose weight, retain or even build muscle, and you will have the energy you need to get through your day.

James Dixon
James Dixon
James Dixon is a fully qualified personal trainer, with a decade’s worth of experience under his belt. Throughout his career, he has helped hundreds of people to meet their dietary and fitness goals, writing exercise and nutrition plans to suit any and every requirement.
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James Dixon
James Dixon
James Dixon is a fully qualified personal trainer, with a decade’s worth of experience under his belt. Throughout his career, he has helped hundreds of people to meet their dietary and fitness goals, writing exercise and nutrition plans to suit any and every requirement.
Have a question? Contact us