This Diet Burns Fat Like No Other—and You've Probably Never Heard of It

Updated 11/28/19
A typical meal on the keto diet: a plate of scrambled eggs and smoked fish
Jonathan Gregson / Getty Images

The ketogenic diet is having a moment. Scientists are beginning to discover that the diet—which burst on to the nutrition scene around 2018—reduces inflammation in the brain (which could help to prevent strokes), has the potential to ease pain for chronic sufferers, and could prevent the onset of diabetes due to its low sugar content.

The low-carb plan may sound similar to the Atkins or Paleo diets, but the keto diet (as it's also known) focuses on heart-healthy fats, moderate protein, and very few carbohydrates. Goop has dubbed it ideal for those "who want to lose weight but have trouble kicking sugar cravings." It can also turn your body into a fat-burning machine.

By now, we all know that fat isn't the enemy and that eating "good" fats doesn't necessarily make you fat. According to advocates, follow the keto guidelines, and you'll be able to hack your body so it can reap the health and fat-loss benefits of a keto lifestyle.

What is the ketogenic diet?

Unlike most diets, the ketogenic diet is pretty science-heavy. We'll keep it light, we promise.

Our brains are like a hybrid car. They use fuel from glucose and ketones to function. When the brain is denied glucose, it will switch to ketones instead. Carbohydrates convert to glucose in the gut, whereas fats convert to free fatty acids (FFA) before converting to ketones in the liver. Deny your body carbohydrates, and the brain will turn to ketones as its primary source of fuel. Increase the FFA in your body, and you'll start producing ketones at an accelerated rate. As these ketones accumulate, your body switches to a metabolic state known as ketosis, which is the end goal of the ketogenic diet.

"During ketosis, there is a decrease in the production and utilization of glucose. There is also a decrease in the breakdown of protein (found in your muscles) to be used for energy," says nutritionist Kelly LeVeque. "So your body burns fat, without sacrificing any muscle—your basic low-fat diet can't say the same. This is the only known 'protein-sparing' weight-loss technique, therefore, many individuals use ketogenic diets to lose body fat while maintaining muscle mass and keeping their metabolism running."

Meet the Expert

Kelly LeVeque is a holistic nutritionist, celebrity health coach, and author of the Body Love book series.

But surely if you're eating more fat, you will just burn the fat you consume? Not so. The ketogenic diet gets our body to utilize fat stores as fuel by affecting two hormones: insulin and glucagon.

"Restricting carbohydrates from the diet decreases insulin and increases glucagon. As a result, our bodies quickly move from storage mode to burn mode—we release triglycerides from fat cells and burn FFA, producing ketones as brain fuel. In addition to insulin and glucagon, a number of other hormones are also affected, all of which help to shift fuel use away from carbohydrates and towards fat," explains LeVeque.

How long will it take to see a difference?

This, of course, depends on your starting point. The more you have to lose, the quicker you will see results, which is the same for any diet. "Due to the removal of carbohydrates in the diet, the body will begin to hold on to fewer fluids and immediate weight loss can be seen, but not necessarily from body fat," says Liam Mahoney, nutritionist for protein brand Grenade. "The positive effects of a ketogenic diet are typically brought about after a period of 18 to 24 weeks of strict adherence," he adds.

Meet the Expert

Liam Mahoney is a sports nutritionist and national account executive for lifestyle and protein bar brand Grenade.

What are the benefits?

There are quite a few benefits of going ketogenic. For starters, by denying your body carbohydrates, you're essentially going on an intense sugar detox, and it's no secret that too much sugar intake can lead to type-2 diabetes and has even been found to prematurely age our skin.

As mentioned above, scientists have discovered that the keto diet has anti-inflammatory benefits, especially in the brain, which benefit those with epilepsy and other neurological illnesses.

The obvious benefit is fat loss, and studies have proven that the ketogenic diet works better than a low-fat diet at triggering weight loss.

"Following a ketogenic diet may also have positive effects on lowering the body's LDL cholesterol levels while increasing HDL cholesterol and reducing the risk of heart disease. Certain studies suggest that ketogenic diets may 'starve' cancer cells. Usually, cells found in our bodies are able to use fat for energy, but it is believed that cancer cells cannot metabolically shift to use fat rather than glucose," says Mahoney. A 2017 study published in Nature suggests that sugar could play a part in the multiplication of cancer cells.

Sounds too good to be true… What are the cons?

If you ditch carbohydrates and you're limiting your fiber intake, constipation can be a real problem. Ensuring your daily carbohydrate intake (more on the specifics later) consists of leafy greens will help ease the symptoms. Still stuck (pun intended)? Try a fiber supplement, such as Metamucil Psyllium Fiber Powder Supplement ($35).

"Keto flu" is another common side effect. Some people who switch from glucose to ketones for fuel find that they suffer from flu-like symptoms: Headaches, nausea, upset stomach, sniffles, "brain fog," and fatigue. You may experience one, none, or all. Luckily, once your body adjusts to ketosis, the symptoms should subside. In the long-term, you should find that your energy and focus improve.

Since you may feel lethargic on the keto diet to start with, it's worth taking your exercise routine down a notch. In the long run, there are strategic ways to eat carbs to fuel your workout without taking your body out of ketosis. "Without carbohydrates, which are needed for energy, it can be very hard to sustain your hot yoga and HIIT class. For this reason, individuals who wish to use a ketogenic diet to burn body fat and still go full-force with their workouts must integrate carbohydrates," says LeVeque.

"There are two ways to do this: You can consume carbohydrates immediately before and after exercise to sustain performance without affecting ketosis, or you can alternate periods of ketogenic dieting with periods of moderate carbohydrate consumption. The period of carbohydrate eating is a must to sustain explosive or demanding exercise," she adds.

Is it safe?

We know that the keto diet doesn't sound wholly good for you, and it doesn't suit everyone. If you are diabetic, pregnant, or breastfeeding, or you're on medication for high blood pressure, then you should consult a doctor before embarking on a ketogenic diet. In fact, "if you have any pre-existing medical conditions, it's always better to consult your GP first," warns Mahoney.

If you're obese, then you're likely to find that the ketogenic diet could have effective and long-term results for you. One 2012 study followed 19,000 people on the keto diet and found it to be "safe, fast, inexpensive, and [had] good one-year results for weight maintenance."

Mahoney does caution that "no diet is a one-size-fits-all solution, and any extreme alteration to your diet should be followed carefully, assessing your mood, energy levels, and sleep patterns on a regular basis to understand the effects it is having on you."

OK, how do you do it?

The idea is to focus roughly 60% to 75% of your diet on good, healthy fats like avocado, MCT, or coconut oil and low-carb nuts like almonds. You want to eat a moderate amount of proteins (around 15% to 30%) like meat and oily fish. Your carbohydrates should be limited to leafy greens and shouldn't exceed 10% of your calories. Check out the KetoDiet Buddy, an online tool that helps you to calculate the correct percentages for you based on your sex, weight, height, and activity level.

A typical day on a Keto diet looks like this:

Breakfast: Eggs scrambled with coconut oil or butter. To boost your ketone production, you could skip breakfast and drink a bulletproof coffee (black coffee blended with MCT or coconut oil and butter or ghee).

Lunch: Chicken breast with herb butter and greens.

Dinner: Low-carb cheeseburger.

You can find a 14-day ketogenic meal plan, complete with recipes at Diet Doctor.

If you find that you miss carbohydrates, then you can supplement with alternatives, such as Miracle Noodle's Shirataki Konjac Rice ($14), a zero-carbohydrate alternative made from konjac (a good source of fiber). Alternatively, you can try making keto bread.

Sugar cravings can also be an issue on the keto diet. If you're struggling, Ruled Me has some keto-friendly dessert recipes.

How do you know when you have reached a state of ketosis?

For most people, it takes around four to 14 days to reach a state of ketosis. One unfortunate signal that your body is producing those all-important ketones is bad breath. This is caused by one particular ketone called acetone (yep, the stuff found in nail polish remover), which is produced as a by-product of the excess fat intake. It should subside after a week or two, and not everyone suffers from it. 

The most reliable way to know if your body has switched to ketosis is to test your urine using Perfect Keto's Ketone Testing Strips ($8). 

Important question: Can you drink alcohol on the keto diet?

You should be drinking water on the keto diet. You may experience some water retention when you're first transitioning to ketosis, but by drinking water regularly, your body will know it has a regular supply and won't feel the need to store it. Coffee with a little cream (or full-fat milk if you're in a bind) is allowed, as is sparkling water—plain or flavored with a little lemon and lime. 

As for alcohol, it's best to hold off until your body is in ketosis, as it could hamper your progress. Then, the best choices are tequila or vodka with soda and fresh lime juice. Alternatively, the odd glass of Champagne, Prosecco, or wine won't do any harm. The good news is that once you have switched your body to ketosis, a few drinks won't completely derail the process. Your body will easily adapt back to ketosis once you eat high fat again. 

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