21-Day Keto Magic

Eat Healthy, Burn Fat, Lose Weight, and Keep It Off


By Dr. Michael Mosley

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See results in three weeks, with a revolutionary keto diet program from Dr. Michael Mosley, the #1 New York Times bestselling author of The Fast Diet.
Recent studies have shown that a keto diet not only produces significant—and rapid—weight loss, but also has many other benefits for long-term health. But it must be done the right way. In 21-Day Keto Magic, Dr. Mosley presents the latest science on the ketogenic diet—a diet high in fat and protein and very low in carbs—explaining how it works and why it is so good for you. The aim of a keto regime is to kickstart a process called ketosis, whereby your body goes from burning sugar to burning fat for fuel. Flipping this metabolic switch has the added advantage of making you feel less hungry, which makes the diet highly motivating and relatively easy to sustain.
21-Day Keto Magic offers a detailed, step-by-step program, along with easy tips and clear advice on which foods support ketosis and which ones stop it, how to tell if you are producing ketones, and how to ensure that you're following the diet safely. There are also 50 delicious recipes from Michael's wife, Dr. Clare Bailey, as well as shopping lists, weekly meal planners, and all the other tools you need to ditch stubborn fat and transform your health for life. 




How we got fat

I don’t think any of you will be surprised to hear that obesity is a very common problem worldwide. But it is shocking when you realize just how recently—and how quickly—the world got fat.

Since I was a medical student, 40 years ago, rates of obesity have almost tripled. Two billion adults are now overweight or obese, as are 39 million children under the age of five. If you look at the world’s major economies, the United States has the highest rates of obesity, closely followed by Mexico, New Zealand, Hungary, Australia and then the UK.1

Most of us get fatter as we get older. Between the ages of 20 and 50 we typically put on weight at a rate of about 1 pound a year. This doesn’t sound that bad, but it means you can find yourself in late middle age 33 pounds heavier than you were in your twenties.2

That’s what happened to me. I was under 167 pounds when I was in my early twenties, and 30 years later I had not only put on about 33 pounds but had also developed Type 2 diabetes. Despite the fact that I was snoring the house down and having to buy ever-larger trousers, neither Clare nor I really noticed what was going on. Because it happens so gradually, most people who are overweight or obese, have, like me, little idea how bad things have gotten. A survey by researchers from University College, London, found that only 11 percent of women and 7 percent of men with a BMI over 30 realized that they were obese.3

Large waists are now so common we have gotten used to them. Being a bit on the chubby side is entirely normal. Muffin tops and double chins are everywhere. And, while the fat acceptance movement is right to challenge the stigma around obesity, and celebrating curviness has been, in many ways, a desirable response to unrealistic skinny supermodels, it remains a sad fact that too much fat in the wrong places has serious health consequences.

Which is why, along with the expansion of our waists, there has been a surge in people needing to be treated for weight-related cancers, joint problems, infertility, hypertension and raised blood sugar levels. Around one in three middle-aged people in the UK, United States and Australia have metabolic syndrome (a combination of diabetes, raised blood fats, high blood pressure and obesity), which puts them at increased risk of heart disease and stroke. It also increases the risk of dying prematurely.

Covid-19 has turned this from a distant to a more immediate threat. If you have an underlying health condition, like metabolic syndrome, and contract the virus, then you are also six times more likely to end up in the hospital and 12 times more likely to die.4

The “fat makes you fat” fallacy

If you look at graphs showing rates of obesity in the U.S. from 1960 till the present day, you will see a relatively flat line from 1960 to 1975. Then rates start to shoot up, for every age group, from teenagers to 60-year-olds, and every ethnic group.5

So what happened? Some blame less exercise, poor sleep or increased anxiety. Others blame the increasing gap between rich and poor. For a long time, it was thought that we were becoming fat because we were eating too much fat; then it was because we were eating too much sugar. I think the evidence points elsewhere. But I will come to that in a moment. Let’s first take a quick look at the usual suspects, beginning with fat.

To understand how fat became top villain in the diet wars, we need to go back to 1957, when the American Heart Association went on a mission to persuade the American public to eat less of it. Their real target was saturated fat, which was seen as a major driver of heart disease, but the idea of “good” fats and “bad” fats was thought to be too difficult for the public to grasp, so the message was simply “cut out the fat.” People were encouraged, for example, to cut the fat off meat, eat low-fat dairy products and replace butter with margarine spreads.

The upshot was that, in time, they reduced their intake of beef and full-fat milk, but they didn’t pile their shopping carts instead with healthy stuff, such as fruit and veggies. No, they now ate ever-increasing amounts of heavily marketed, sugary carbohydrates (in the form of low-fat cakes, cookies, fizzy drinks, etc.) and lots of vegetable oils, sales of which soared.

Most of those vegetable oils were highly processed. To turn oil into margarine, the manufacturers used a process called hydrogenation, which in turn led to the production of trans fats. Trans fats, until recently found in most store-bought cookies and cakes, are the Lord Voldemort of the fat world. They are major triggers of heart disease. They have been largely phased out.

And further collateral damage was caused by the fact that the “war on fat” didn’t really distinguish between different types of fat. We now know, for example, that the sorts of fat that you find in nuts and oily fish are good for our hearts and our waistlines. Yet to many supporters of the low-fat diet this was heresy.

One of the early and most controversial supporters of the idea that there are “good fats” and “bad fats” was Professor Hugh Sinclair, a rather eccentric academic based at the University of Oxford. In the 1940s, Professor Sinclair had traveled to northern Canada to study the Inuit and had become intrigued by their high-fat diet and low rates of heart disease. He wondered whether omega 3—an essential fatty acid found in oily fish—was protecting the Inuit from heart attacks. In 1956, he wrote a letter to the Lancet, entitled “Deficiency of essential fatty acids and atherosclerosis.” In it he argued, among other things, that heart disease was the result of consuming too little essential fatty acid, rather than too much.

This letter led to such a storm of criticism that for the next 20 years Sinclair retreated from the medical mainstream. Eventually, in the early 1970s, he decided to test his theory by putting himself on an Inuit diet, eating nothing but seal, oily fish, mollusks and crustaceans. Throughout his experiment, Sinclair measured his bleeding time, the time it took for his blood to clot, by cutting himself every week (he did this because blood clots are one of the key causes of heart attacks and strokes).

While making a series for the BBC on self-experimenters, I decided to repeat his experiment. We tried to import seal from Canada, but it got impounded by customs, so I lived on nothing but fish. Sinclair stuck to his diet for three months; I managed a few weeks.

On his new diet, Sinclair’s bleeding time increased from three minutes to a terrifying 50. Mine doubled.

Sinclair had found part of the reason why eating fish oils is so good for the heart: it reduces the tendency of platelets to stick together and thus the risk of forming clots. Since then, many other studies have shown that eating oily fish not only reduces your risk of heart attacks, strokes and death from heart disease, but may also lead to slower rates of mental decline.

Other studies have shown that people who eat fish regularly are much less likely to become depressed and that supplementing your diet with omega 3 can reduce depression.6 It has also been shown that people who eat oily fish at least once a week have more gray matter in areas like the hippocampus, which is responsible for memory.7

Clare and I are big fans of fish, and lots of our recipes are fish based. As well as being rich in omega 3, oily fish is a great source of high-quality protein. Moreover, eating fish has a much lower impact on greenhouse gases than eating meat.8

The Mediterranean diet

These days fat, at least in part, has been rehabilitated. The Mediterranean diet, widely seen as one of the healthiest diets on the planet, is actually quite high in fat. That’s because, as well as plenty of vegetables, fruit and legumes, it contains lots of oily fish, nuts and olive oil.

In a really important study called Predimed, 7447 men and women were randomly allocated to either a standard low-fat diet or a higher-fat Mediterranean diet, in which they ate at least three portions of fruit and vegetables a day, plus fish and legumes (peas, lentils, beans) a minimum of three times a week.10 They were also encouraged to eat nuts and olive oil and allowed the occasional glass of wine with their meal.

Not surprisingly, people on the Med diet were far more likely to stick to their regimen than those on the low-fat diet. Indeed, this trial was stopped early because those on the higher-fat Med diet were doing so much better than those on the low-fat diet, with 30 percent fewer heart attacks and strokes.

When you look at a breakdown of the macronutrients that people allocated to the Mediterranean diet were eating, it comes in at 41 percent fat, 41 percent carbs and 18 percent protein. It is a diet that is much higher in fat and protein, and lower in carbs, than the sort of diet we are normally recommended.

The rise and fall, rise and fall, then rise again of low-carb diets

Although mainstream medicine has long favored low-fat diets, for many people it is carbs that are the problem. The thing about carb-rich foods, like cookies, cake or white rice, is that they are swiftly broken down in your body into sugars, which then cause your blood sugar levels to soar. Your body responds by releasing the hormone insulin, which brings your blood sugars back down again. But a rapid rise and then fall in your blood sugar levels (a blood sugar crash) can make you ravenously hungry. I find that if I have cereal or toast for breakfast, then a couple of hours later I really want to snack. Whereas if I eat something protein-rich, like an omelette, I stay full until much later in the day.

There are good carbs and bad carbs. Many fruits and vegetables are rich in carbs, but they also contain lots of fiber, so your body finds these sorts of food harder to break down. Not surprisingly, you get much smaller blood sugar spikes after eating an apple than after eating an apple pie.

Eating lots of processed carbs, like white rice and packaged bread, is fine if you are doing lots of exercise or hard manual labor, because your muscles will burn through the sugar that is flooding your body. But if you just sit around after a carb-heavy meal, your insulin levels will surge, as your body struggles to bring those blood sugar levels down. And the way insulin does this is by tucking those excess calories away in your fat stores. Your body has good reasons for doing this—it cannot tolerate high levels of sugar in the blood—but the fact remains, when insulin goes up, fat-burning goes down. And if you have high levels of insulin circulating, it also means there are fewer calories in your bloodstream for the rest of your body to use. So you get hungry and overeat.

Another problem is that our bodies did not evolve to deal with the huge amounts of sugar that we currently consume. So over time, as our levels of body fat rise, we develop something called “insulin resistance.” Our cells become resistant to the impact of insulin, so our pancreas has to crank out more and more of it to get our blood sugars down. This leads to prediabetes (where your blood sugars are raised, but not yet in the diabetic range), and unless you change your diet and lose weight, it often progresses to Type 2 diabetes and fatty liver disease.

One obvious way to counter this is by eating fewer highly processed carbs.

The first low-carb diet

One of the first people to write about the benefits of going on a low-carb diet (though he didn’t call it that), and capture the public imagination, was William Banting, a 19th-century Victorian undertaker who, among other things, prepared elaborate burials for members of the royal family.

Banting’s problem was that he was obese; just five and a half feet tall, he weighed over 200 pounds. His obesity was so bad that he had to go down the stairs backwards, and on his knees. He had tried everything to lose weight, from Turkish baths to huge amounts of rowing. The trouble was that all the exercise did was make him hungry.

And then, in his early sixties, he went off to visit Dr. William Harvey. Dr. Harvey told him to cut out sweet, starchy foods, like buttered toast and pastries, and instead stick to meat, fish, vegetables and unsweetened tea. Beer was out, but he was allowed gin, whisky or brandy (all of which are low carb).

Banting stuck to the diet and lost 35 pounds in 36 weeks. He could now walk downstairs, forwards, felt better than he had for years and claimed that his hearing and eyesight had both improved. He wanted to share the good news, so in 1863 he published a pamphlet called “Letter on Corpulence: Addressed to the Public.”

You can find it online; it is a very short but entertaining read and in many ways, it is surprisingly modern. Banting starts by claiming that, “Of all the parasites that affect humanity, I do not know of, nor can I imagine, any more distressing than that of Obesity,” before going on to explain his new diet in a very succinct form:

For breakfast, I take four or five ounces of beef, mutton, kidneys, broiled fish, bacon, or cold meat of any kind except pork; a large cup of tea (without milk or sugar), a little biscuit, or one ounce of dry toast.

For dinner, five or six ounces of any fish except salmon, any meat except pork, any vegetable except potato, one ounce of dry toast, fruit out of a pudding, any kind of poultry or game, and two or three glasses of good claret, sherry, or Madeira—champagne, port and beer forbidden.

For tea, two or three ounces of fruit, a rusk or two, and a cup of tea without milk or sugar.

For supper, three or four ounces of meat or fish, similar to dinner, with a glass or two of claret.

For nightcap, if required, a tumbler of grog (gin, whiskey, or brandy, without sugar) or a glass or two of claret or sherry.

And that was it as far as Banting’s dieting advice went. But his pamphlet struck a chord; it sold like crazy, and the first low-carb diet was born. Banting himself lived to the ripe old age of 82; he died of pneumonia.

The Atkins diet

After Banting’s death, interest in his diet faded away and it would be a hundred years before another low-carb diet book caught the public imagination in such a vivid fashion. This time it was Dr. Atkins’ Diet Revolution, which was published in 1972. Written by a former cardiologist, Robert Atkins, who had lost lots of weight by going low carb, it became one of the bestselling books of all time.

Doctors hated the Atkins diet, which focused on eating foods like cream, cheese, bacon and red meat, while avoiding potatoes, rice and whole grains. But most people who tried it lost weight without having to worry about calories, which is why it became insanely popular.

The Atkins empire rose to giddy heights (at one point 10 percent of Americans were said to be on the Atkins diet)… and then it all fell apart. In 2003, Robert Atkins died, after slipping on ice and hitting his head. Although his widow refused to allow an autopsy, his medical records were leaked. These revealed that at his time of death he was hugely overweight and had signs of advanced heart disease. In 2005, the company he had founded, Atkins Nutritionals, filed for bankruptcy.

But the low-carb diet didn’t die, and many doctors, particularly those who see and treat patients with Type 2 diabetes, became interested. One of them is a GP, called Dr. David Unwin, whom I know very well.

Dr. Unwin’s breakthrough trial

As a GP, David had, for most of his life, given his patients the conventional low-fat advice. But he had become gloomy about its impact. He told me that between 1986 and 2012, there was an eightfold increase in the number of patients in his practice with Type 2 diabetes, many of them shockingly young.

Then, in 2012, a former diabetes patient turned up, 10 percent lighter and free of diabetes. “She mystified me. But I am always fascinated by stories of success so I asked her what she had done.”

She replied, “You’re not going to like this, doctor.” She had read about the benefits of a low-carb, high-fat diet and given it a go.

David did some research and decided to do a small trial. He recruited 19 patients who had Type 2 diabetes or prediabetes and gave them a very simple diet sheet.

“Reduce starchy carbohydrates a lot (remember they are just concentrated sugar),” it read. “If possible, cut out the white stuff like bread, pasta, rice. As for sugar, cut it out altogether, although it will be in the blueberries, strawberries and raspberries you are allowed to eat freely.”

Instead, patients were encouraged to eat more protein, butter, full-fat yogurt and olive oil: “Eating lots of veg with protein and fats leaves you properly full in a way that lasts,” he wrote in capital letters.

The patients who took part in this early trial started out with an average weight of 220 pounds and over the eight months of the trial lost over 20 pounds, much of it around the waist.

By the end, only two of the 19 still had raised blood sugars and even they had seen a huge improvement. There were also big improvements in blood pressure and cholesterol levels, despite the fact that his patients were now eating far more eggs and butter.

Since then, David, who is an expert clinical adviser for the Royal College of GPs, has helped more than 100 patients with Type 2 diabetes come off drugs and published more studies. He, and other GPs like him, have not only changed their patients, but also changed how doctors view low-carb diets, particularly in the context of Type 2.

Ultra-processed foods—the real villain

Although I believe that lower-carb diets can be very helpful, particularly for people with Type 2 diabetes, I don’t think that most people get fat simply because they are eating a lot of rice and potatoes. It is also hard to blame sugar for the present obesity crisis, as consumption of sugar has been falling in most developed countries over the last decade, while rates of obesity have been rising. And as I regularly point out to people who claim that sugar is addictive, I feel no compulsion to eat sugar cubes or dip a spoon into a bowl of sugar and snack on that. Nor, I suspect, do most people.

No, I think the real villain, the main driver of obesity worldwide, is the rise and rise of ultra-processed food, the sort of brightly packaged, aggressively marketed products that fill our supermarket shelves. Typically, they are high in both fat and sugar, along with mysterious preservatives and emulsifiers (E numbers). I suspect the main reason that David’s patients are losing weight and getting healthier is not just that they are cutting down on the carbs, but that they are eliminating the ultra-processed foods. We are going to take a closer look at the science behind this claim in the next few pages.

What is an ultra-processed food?

In 2009, a team, led by Carlos Monteiro, Professor of Nutrition and Public Health at the University of Sao Paulo in Brazil, published a hugely important paper called “The issue is not food, nor nutrients, so much as processing.”11

They argued that while people have, for decades, been blaming fats and carbs for the rise in obesity, they have largely ignored the importance of processing, the extent to which the foods we eat have been manipulated and altered by the big food manufacturers before they reach our plates.

So, they set about identifying different categories of food, ranging from those that have been minimally processed to those that are ultra-processed, and created the NOVA classification system.12

NOVA breaks down foods into the following groups:

Unprocessed or minimally processed foods

These are foods that are fresh, frozen, pasteurized, fermented, bottled or packaged. They are not all completely untouched, as nature intended them, but whatever processing they have been through is minimal. The important thing is that there are no added sugars, oils or fats.

Foods that fall into this category include: fruit, vegetables, rice, legumes (i.e. lentils, chickpeas), meat, poultry, fish and seafood (fresh or frozen). Then there are eggs, oats, pasta, couscous and polenta. Nuts, without added salt, are also part of this group, as are herbs and spices, milk and plain yogurt, tea, coffee, and water.

Processed foods

These are often foods taken from the first group, with a bit of salt or sugar added. They include fresh bread, salted, cured or smoked meats, canned fish, canned fruit, butter, cheese, wine and beer.

Ultra-processed foods

The foods in this group are not so much foods as formulations: they are made in factories and are designed to imitate the taste and smell of fresh or minimally processed foods, while actually being produced out of cheap industrial ingredients and additives. They contain lots of sugars, fats and salt, as well as, according to the World Nutrition Journal in 2016, “dyes and other colors, color stabilizers, flavors, flavor enhancers, non-sugar sweeteners, and processing aids such as carbonating, firming, bulking and anti-bulking, de-foaming, anti-caking and glazing agents, emulsifiers, sequestrants and humectants.”

The reason manufacturers add these strange-sounding ingredients to their products is to give them a long shelf life and to make them “hyperpalatable.” In other words, to keep us coming back for more. The ultimate aim of the Big Food manufacturers is, of course, to make Big Bucks. And they certainly do.

The foods in the group include some pretty obvious candidates, like chicken nuggets, burgers, chips, pizzas, hot dogs, pre-packaged meals, fizzy drinks and packaged fruit juices. But it also includes most mass-produced breads (brown as well as white, just look at what it says on the label), store-bought cookies, cakes, buns and sweetened breakfast cereals.

Mass-produced ice cream, fruit yogurts, chocolate, sweets, potato chips, energy bars, margarine and pretty well anything that says “instant”– i.e. instant noodles, soups, desserts—also fall into this category.

Vegans and vegetarians are being increasingly targeted with ultra-processed convenience foods, such as vegan sausage rolls. Just because it’s plant based doesn’t mean it’s healthy.

How can you spot an ultra-processed food? Read the label. If there are five or more ingredients—and those ingredients include numbers or have names you don’t recognize—the chances are it’s ultra-processed.

Sue’s story

Sue Bernard, a former IT manager, knows exactly what it is like to be in thrall to ultra-processed food. In her case, the problem was late-night grazing.

I would have a healthy dinner, and then after dinner—I was dreadful. I ate chips and chocolate and ice cream. It was non-stop. It was a complete compulsion. And I would even say to my husband, “Why am I doing this? Why am I going back into the kitchen to open the fridge and eat more chocolate when I know I cannot be hungry?” It was almost as if I had a fat wish; we talk about a death wish but this was definitely a fat wish. It was as if I wasn’t in control.

I was stick thin as a child. We didn’t have a car, I walked everywhere. Until my first son was born, I was 125 pounds and a size eight. Then I had three children and with each child I put on a bit of weight and didn’t lose it. Over the years I’ve tried different ways to lose weight but none of them worked. The catalyst moment was when I saw a photo of myself and I thought I can’t share that—I look huge. I remember the moment incredibly clearly—it was December 10, 2020.

At that point, Sue was 200 pounds. She had arthritis in her knees and constant back pain:

All the problems you have when you are hugely overweight. And I kept thinking, I’m not going to live to see my family growing up.

She saw my Channel 4 documentary, “Lose a Stone in 21 Days,” and decided to put herself on my diet.

I saw those people lose all that weight and I thought, “I can do that.” I decided this would be the start of a new life. It was as if a switch went on in my head.

To start with it wasn’t easy:

A couple of nights in the first week I wanted desperately to eat chocolate or ice cream so I went to bed. I started drinking lots of water. In the morning I started drinking black coffee instead of white coffee so I could still enjoy my coffee.

I lost 35 pounds in the first 12 weeks and then I switched to the 5:2 diet. I have now lost 60 pounds. I went from a size 16 to a size 10. Though to be honest it’s not really about being size 10, but I know that being size 10 means that I’m healthy.

Now that I’ve lost the weight I can bend my knees, something I couldn’t do before.

We have a couple of small dogs and I do take them out for a walk every day, a couple of miles. When I realized I could move more I joined a local gym and three or four mornings a week I go to the gym and do the bike and the rowing machine. I do crunches and stretches.

How do I keep on course? I always plan. It is a way of life and not just a way of eating. I don’t want the sweet things anymore, I don’t crave them.


On Sale
Apr 5, 2022
Page Count
288 pages
Little Brown Spark

Dr. Michael Mosley

About the Author

Michael Mosley trained as a doctor before becoming a journalist and television presenter. He is the author of The FastDiet, The 8-Week Blood Sugar Diet, The Clever Guts Diet and The Fast 800. He is married with four children.

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