The ketogenic diet: What is keto, and does it work?

Keto diet overview

Imagine being able to eat all the fat you ever wanted and still lose weight. Butter, burgers, bacon, steak, cheese—no restrictions. Except maybe one. In exchange, you’d have to forgo nearly all carbs like bread, bagels, pasta, pizza, and even most fruit. In reality, that’s the trade-off required for keto-diet success.

Although it may sound new, the ketogenic diet (or “keto” for short) was developed nearly a century ago by Mayo Clinic physician Russel Wilder, MD, to treat epilepsy. Now it’s one of the hottest weight-loss crazes.

The basics of the ketogenic diet are high fat, moderate protein, and very little carbohydrates. The typical ratio is 70-80 per cent fat; about 10-20 per cent protein; and about 5-10 per cent carbohydrates.

The initial weight loss is attributed mostly to water loss from the dramatic reduction of carbohydrates. When you eliminate nearly an entire category of foods—in this case, carbohydrates—you are left with far fewer foods to eat and will therefore likely be eating less.

Second to consuming less, when you get most of your calories (a.k.a. kilojoules) from fat, it forces your body into a state called ketosis, whereby your body derives its energy from ketones instead of glucose.

What is ketosis?

Lots of people assume keto is a high-protein diet, but it’s actually much higher in fat. On the flip side, it’s extremely low in carbs, with just 5 per cent to 10 per cent of calories coming from carbohydrate food sources. Considering most of us consume roughly half of our calories from carbs, adopting a keto lifestyle could mean a lot of changes.

The goal of the keto diet is to force the body into ketosis, a metabolic condition in which the body burns fat in place of its preferred fuel source, carbohydrates. “Ketosis is a back-up system for the body to use when it doesn’t have access to food, such as in times of starvation,” says Toby Amidor, MS, RD. “It is not meant as a long-term way to provide the body with energy.”

What happens when your body doesn’t get the carbs it needs for fuel? First, it burns available sugar stores known as glycogen, releasing water—and water weight—in the process. It’s why many people experience rapid rates of weight loss in the first few days and weeks on a keto diet—and why the reintroduction of carbs, which replenishes glycogen and water stores, reverses water weight loss.

Next, the body breaks down protein to produce the simple sugar glucose, the body’s favourite source of energy. This neat trick is called gluconeogenesis. Trouble is, only a limited number of amino acids can be converted to glucose, so this process only covers a fraction of the body’s energy needs.

Following the use of glycogen and water losses, and a brief spell of gluconeogenesis, the body eventually turns to its last possible fuel option: Fat. However, because fat can’t cross the blood brain barrier to power the brain, it’s converted it into a form the brain can readily use—namely an alternative form of energy called ketones, a fat byproduct produced by the liver. When your body uses ketones for energy instead of its usual glucose, you’re effectively in ketosis.

​How does consuming more fat than carbs on keto lead to weight loss?

Considering fat has more than twice as many calories per gram as carbohydrates, you might be wondering how eating more of it can help you lose weight. “The focus on fat and proteins appears to promote satiety, making it easier to restrict calories,” says Jeffrey Volek, PhD, RD.

But there’s another incredibly basic reason why the keto diet works, at least in the short term. When an entire food group (carbs) comes off the table, you’re left with fewer foods to choose from, making it easier to eat less. And just like on any other diet, when you cut calories, you lose weight.

Despite dramatic claims surrounding the keto diet, it’s unclear how long the results last. In the first couple of weeks, you can expect rapid and substantial weight loss. Yet that’s mostly from the diet’s diuretic effect: Tapping into your body’s sugar stores leads to the release of fluids. But as soon as you bend the rules you replenish your sugar—and fluid—stores, and the water weight returns.

Even though some studies show the keto diet has a small edge over a low-fat diet plan in the short term, many keto followers start to regain some of their losses in as little as five months.

​Potential health benefits of a keto diet

Even though keto can be super restrictive, it could offer some health benefits. A small number of studies show it may reduce symptoms of Alzheimer’s and Parkinson’s diseases and improve hormone profiles in women with polycystic ovary syndrome (PCOS). Right now, experts agree more long-term research is needed.

There is, however, stronger evidence that lower- and low-carb diets may help lower blood sugar in people with type 2 diabetes. “Several studies have reported that the keto diet can significantly reduce (a long-term marker of blood sugar control known as) HbA1c in individuals with diabetes when compared to a traditional low-fat, moderate carbohydrate eating plan,” says clinical dietitian and diabetes educator, Patti Urbanski. In fact, a diabetes therapy study found that when people with diabetes combined a ketogenic diet with other treatment methods for one year, 94 per cent of them were able to lower or eliminate their insulin requirements and reduce the need for most other medications by 48 per cent. Again, more research is needed to uncover the optimal approach for people living with diabetes.

What do you eat on keto?

Fats, proteins, and minimal carbohydrates are what you need to eat to be successful on keto. Carbohydrates will make up a significantly smaller portion of your diet on keto than on an average healthy eating plan. On keto, you would have to eliminate most carbohydrates, including obvious sources like bread and pasta, and less obvious sources, like fruits and veggies.

Keto approved foods

Foods to avoid on a keto diet

For the keto diet to work, you’ll need to reduce carbs—a lot! Sure, you’ll avoid nutritionally empty desserts, lollies, and sweetened drinks. But you’ll also have to say goodbye to healthy wholegrains, potatoes, beans, most fruits, and even many veggies. “With so many foods being eliminated or eaten in small amounts, there’s no viable way to take in adequate nutrients your body needs to stay healthy,” Amidor says. “Since fruits, grains, and carb-containing vegetables are limited, nutrients like fibre, antioxidants, potassium, magnesium, and vitamins A and C are especially of concern as this may lead to multiple nutrient deficiencies.”

Food categories you’ll eliminate on the keto diet:

1. Grains and starches

Wholegrains like brown rice, quinoa, oats, wholemeal pasta, and wholegrain bread work wonders for healthy digestion. But you won’t find them on a keto diet. Filling your plate with fibrous veggies like broccoli, asparagus, cauliflower, Brussels sprouts, kale, and chard can help to some degree, but constipation may still be an issue.

Without grains, you may also have difficulty obtaining the magnesium your body requires for more than 300 different chemical reactions, such as maintaining healthy nerves and muscles, building protein, helping your body use glucose efficiently, and regulating blood pressure. Magnesium can be found in keto-approved almonds, spinach, cashews, and avocados.

2. Starchy vegetables

While keto gives the green light to lots of vegetables, higher-carb potatoes, parsnips, corn, carrots, and beets are off the menu. That can make getting the potassium needed for healthy blood pressure a challenge. It can also rob you of disease-preventing antioxidants.

3. Most fruit, except small portions of berries and melon

Like vegetables, fruit is loaded with antioxidants, not to mention immune-supporting vitamins A and C. And yet? The keto diet outlaws most options. A few exceptions include small servings of lower-carbohydrate strawberries, blackberries, and rockmelon. To keep carbs below seven grams per serving, limit portions to half a cup.

​4. Beans, chickpeas, lentils, peas, and edamame

Most people think of beans and legumes as high-protein foods, but they’re also loaded with healthy complex carbs. Go bean-free and you’ll miss out on one of nature’s top sources of potassium, antioxidants, and fibre.

​5. Some condiments and sauces

A little ketchup, barbecue sauce, or teriyaki sauce is a genius way to infuse foods with flavour for relatively few calories. But on keto, their added sugars make them a no-go. Instead, you need to stick with lower-sugar mustard, soy sauce, and red-wine vinegar.

Check out the chart below for some sources of carbohydrates. There’s not much to eat when the goal for keto is to stay below 30 grams of daily carbohydrates!

Is keto hard to follow?

Many have found keto a workable diet during a focused period of weight loss. Although studies have shown keto can be restrictive and hard to follow over the long term and it can be heavy on red meat and other fatty foods that are increasingly considered to be risk factors for multiple chronic diseases.

Is keto safe?

Perhaps the biggest keto concern is its impact on heart health since it prescribes an unconventionally high dietary fat intake without differentiating between saturated and unsaturated fats. “Some people believe that going on keto is an open invitation to eat bacon, processed meats, and fatty cuts of meat, but that isn't the case,” Amidor says. “These foods are high in saturated fat that’s been linked to heart disease.” While research on keto and heart health has been inconsistent, several studies echo this concern. For instance, one meta-analysis of 11 studies found that going keto resulted in a greater increase in harmful LDL cholesterol than a low-fat plan.

The upshot: Do keto diets work?

The ketogenic diet may be effective for weight loss in the short term, but many experts agree that it’s extremely difficult to follow for a prolonged period of time, and that research on its long-term effects are limited. What’s more, keto diets can be heavy in red meat and other fatty foods, an approach to eating that’s not generally considered healthful.

Keto doesn't align with the Australian Dietary Guidelines, which emphasises eating plenty of fruits and vegetables, wholegrains, and plant-based proteins.

The best eating plans are ones that you can stick with for the long term, include a wide variety of foods, and don’t require you to eat from a list of ‘approved’ foods. Some people have found that keto works well for them, and others have found it can be hard to sustain. Given the potential side effects, health risks, and the emotional toll of trying to maintain such a restrictive diet, there are healthier ways to lose weight.

If you have pre-existing liver or kidney conditions, heart disease or diabetes, you should seek the advice of a doctor before undertaking any significant changes to your diet.