Written by Melissa Mitri, MS, RD

The ketogenic diet, or “keto” for short, remains one of the most popular diets for those looking to lose weight. Does keto help you lose weight, or is it just another fad? Here we’ll discuss the pros and cons of keto, and summarize the latest research on keto and weight loss.

Chances are you know at least one person who has tried keto. You may be asking yourself “well they lost weight and it seemed to work for them, so it probably works right?” Not necessarily, because everyone is different.

If you’re wondeing if the keto diet will help you lose weight, read on to learn how keto works and what the research on keto says.

What is the ketogenic diet?

The keto, or ketogenic diet is a very low carbohydrate, high fat diet that is moderate in protein. The term ketogenic comes from the word “ketosis”, which is a reaction that happens in your body when it doesn’t have enough carbs. Instead of burning carbs for fuel, your body burns fat. This produces a substance called ketones.

It is thought that when these ketones are produced, your body experiences the benefits of a ketogenic diet.

What are ketones exactly?

Ketones are an alternative fuel that your body produces when it doesn’t have enough carbs for energy. Instead, the liver breaks down stored fat in your body. In the research, ketones have also been seen to increase satiety and reduce appetite.

Here are the core features of the keto diet:

Very high in fat – A keto diet is about 70-80% fat, where you are eating at least 100-150 grams of total fat per day. This requires conscious effort and does not always happen automatically.

Very low in carbs – Only 5-10% of your calories on keto come from carbs. This ends up being less than 50 grams of carbs per day, and sometimes as low as only 20 grams.

Moderate in protein – A keto diet is considered “moderate” in protein, where 10-20% of your calories come from protein. The exact amount of protein you need can vary based on different factors such as your age and activity level.

The basic premise of the keto diet for weight loss is if you deprive your body of glucose (which comes from carbs in your diet). In doing this, your body then begins to break down your fat stores for fuel.  

If your carb intake is low enough and your protein intake is moderate (but not too much), your body will transition to a state of “ketogenesis” where it burns more calories from the breakdown of your food. 

Before deciding on whether to try it, it’s important first to know what you can and can’t eat on a keto diet.

What can you eat on Keto?

On a keto diet, fats are promoted most heavily, then protein, then carbs.

High fat – oils, butter, lard, avocado, coconut, some nuts and seeds, meat and poultry

Moderate Protein – grass-fed beef, free-range poultry, pork, bacon, wild-caught fish, organ meats, eggs, tofu, some nuts and seeds

Very Low Carb – 30-50 grams per day – berries, limited amount of dairy

What foods are restricted on keto or need to be avoided?

Here is a list of what you can’t eat on keto:

  • All starches – pasta, rice, bread, bagels
  • Starchy veggies like carrots, potatoes, and corn
  • Legumes – beans, lentils, and peas
  • Simple sugars and sweets – cookies, cakes, candy
  • Soda and sweetened beverages
  • Most fruits except berries
  • Dairy

Pros of the Keto Diet

If you’re still trying to decide if keto is for you, here are the biggest pros and cons of the keto diet.

  • Produces fast weight loss
  • Improves satiety
  • Burns belly fat
  • May improve health markers
  • Many resources available

Produces fast weight loss

One of the biggest appeals of the keto diet is the possibility of quick weight loss. Most people that follow keto tend to lose weight quickly in the beginning, which can be motivating.

There are a few potential reasons for the initial quick weight loss with keto:

  • Water weight loss – In the first few weeks on a keto diet, the weight you lose is primarily water weight. This is because when you consume a very low carb diet, your body rids its body of water. The 5-10 lb weight loss you may see in these early weeks is exciting, but it typically levels off shortly after.
  • Increased fat burning efficiency – Some research points to the possibility that following a keto-style diet offers a “metabolic advantage”. It is said that it preferentially burns fat in the body. Typically, your body burns carbohydrate, or glucose for fuel, but if your diet is very low in carbs, it may burn your body fat instead.
  • Increased thermic effect of food – The thermic effect of a food, or TEF, is the increase in metabolic rate that occurs in the body after consuming a particular type of food. High protein foods produce a higher TEF, which may help you burn more calories after eating. This can increase your metabolism over time. Since the keto diet is fairly high in protein, this is one proposed mechanism into how it helps you lose weight.

Improves Satiety

Many studies have shown those following a keto diet report feeling less hungry. The keto diet is very high in fat and moderate in protein. Both fat and protein are very satisfying nutrients compared to carbs.

However, the ketones produced themselves may reduce the appetite. In other words, when your body transitions to a state of ketosis, these ketones can act as an appetite suppressant.

Burns Belly Fat

There is some evidence regarding the keto diet for burning belly fat. This may be mostly due to the fact that keto is a very low carb diet. Low carb diets have been seen in a few studies to lead to more abdominal fat loss than traditional low-calorie diets.

May Improve Health Markers

In addition to producing weight loss, the keto diet may also improve other non-weight aspects of health. Some examples include decreased triglycerides, lower LDL (the “bad” cholesterol) levels, lower blood glucose (blood sugar) levels, and increased HDL (the “good” cholesterol) levels.

It is important to note that while these benefits have been seen, they have only been studied up to 24 weeks. Therefore it is unknown if these benefits would continue in the long-term.

Many Resources Available

There are a wealth of resources available if you’re looking to start the keto diet. Upon a quick Google search, you’ll come across an array of keto resources. These include keto recipes, keto meal plans, keto diet books, and keto diet tips on how to get started.

When the going gets though this can make things easier and help you find answers to any questions on the diet.

There are even keto meal delivery services out there that can provide keto-friendly meals to fit your diet goals.

Cons of the Keto Diet

While there are some pros to the keto diet, there are equally some surefire cons:

  • Restrictive
  • Not sustainable
  • Expensive
  • Possible side effects
  • Nutritional deficiencies

Restrictive

The keto diet is restrictive in nature, and can be difficult to follow. It also restricts many healthy foods that you may be accustomed to eating. This can leave you feeling unsatisfied.

Many foods that are not allowed on keto are also nutritious foods such as whole grains, beans, and dairy that can assist with weight loss.

Additionally, research has shown that restrictive diets can increase the likelihood of overeating and eating disorders.

Not Sustainable

Because the keto diet is restrictive and difficult to follow in social settings, it’s not very sustainable for most people. It requires a great deal of meal prepping and planning on a daily basis, but may be even more difficult when it comes to eating at a social gathering or restaurant, where carbohydrate-containing meals abound.

And if a diet is not sustainable, it is more likely that you will not be able to follow it long-term and will re-gain the weight back. This is not your fault, this is the fault of the unrealistic diet restrictions themselves!

Expensive

Going keto can be expensive, especially if you opt for all the healthy fat sources such as coconut, MCT, and avocado oils. These oils can be hard to find, and are significantly more expensive per serving than the typical canola or olive oils (which, by the way, are also super healthy).

Many low-cost nutritious foods like beans, legumes, and whole grains are not allowed on keto. On the contrary, higher cost meats and cheeses are more prevalent.

If you’re on a tight budget – keto may not be for you.

Possible Side Effects

There are several possible keto diet side effects to note that you may experience, especially in the first few weeks. These early symptoms are also known as the “keto flu” and include symptoms such as :

  • Fatigue
  • Irritability
  • Brain Fog
  • Exercise Intolerance/Reduced Stamina
  • Digestive Upset
  • Insomnia
  • Light-headedness
  • Weakness
  • Nausea

Some may only experience these side effects during the first 1-2 weeks, while some may not at all. For some, however, the body doesn’t adjust even in the long-term. If that’s the case, this may be a telltale sign the diet isn’t for you.

Nutritional Deficiencies

Nutritional deficiencies are possible on the keto diet. Because you are avoiding certain food groups, nutrients such as vitamin C and D may be lacking. If you are thinking about going keto, consult with your medical doctor or a Registered Dietitian to help you meet your nutrition needs.

What can I expect if I’m starting a keto diet?

If you decide to try keto, there are a few important things to note before you start.

In the first 2 weeks on a keto diet, you may experience what is called the “Keto flu” where you may develop fatigue, lightheadedness, nausea and headaches. 

This is the result of sodium and fluid rapidly exiting your body. This is often the body’s responsea to a very low carbohydrate diet. The large shift in your body’s metabolism can cause these unpleasant symptoms.

So can you lose weight on the keto diet?

In short – yes. Many people successfully lose weight on keto, but the caviat is it likely doesn’t last.

The most weight loss is typically seen in the first 2 months on the diet. If you can get over the keto flu hump, you may feel satisfied and lose weight fairly quickly during this time.

However, there are studies that show after that after a few months, the weight may start creeping back up. The weight loss slows, hunger and cravings return with a vengeance,(often more than prior to following keto) and it becomes more difficult to adhere to. This then creates that vicious diet-binge cycle.

I’ve seen this in many of my clients who have shared their past keto diet experiences with me, and it typically worsens their overeall relationship with their food. Not to mention this can be super frustrating when you initially are so motivated and seeing results, and then all of a sudden you feel like you’re going backwards.

What the keto diet research says

According to much of the research, keto can help you lose weight. However, most of the research on the keto diet has been done up to a 24 week, or a 6-month timeframe. In regards to long-term weight loss results, the keto diet has been seen to show similar results to a traditional low-calorie diet.

Therefore, there is nothing magical about keto and it is a short-term fix. Eventually, you will probably want to add many of the restricted foods back into your diet, or will need to if you become deficient. Then, the weight will start to creep back up.

It is questionable how long keto can realistically be followed long-term.  Restriction can be done temporarily, especially when there is more internal motivation in the beginning of your weight loss journey.  But once you hit a plateau or weight loss slows, it becomes more difficult to stay motivated. 

Following the keto diet puts you at risk for nutritional deficiencies such as magnesium, potassium, and vitamins C and D. It also can cause constipation and digestive issues as it is limited in foods that are natural fiber sources like fruits, beans, and whole grains.

On the other hand, even though the keto diet is very high in fat, it may actually improve cholesterol levels. This may be a result of it’s ability to burn fat and result in weight loss.

Who should not follow keto?

Even though I would not recommend keto in general to my clients, there are a few specific populations where a keto diet is contraindicated.

This includes anyone with a history of an eating disorder or any type of unhealthy relationship with food. The keto diet restricts many foods and puts foods into categories of good and bad. This type of thinking and categorizing of foods only increases the chances of disordered eating behaviors.  

I would also not recommend this diet to anyone who is pregnant, as there is no research on the safety of this during pregnancy. Also during pregnancy and especially if you have morning sickness, carbs and starchy foods often are much better tolerated and sometimes all you can keep down.  

You also need a balanced diet during pregnancy with plenty of fruits and vegetables, many of which are restricted on the keto diet.

Here is a 1-day Sample Keto Meal Plan:

If you do decide to give the keto diet a try, here is a 1-day keto meal plan to get you started.

Breakfast: Smoothie with almond milk, leafy greens, almond butter, and protein powder

Morning Snack: 2 hard-boiled eggs

Lunch: Chicke tenders made with almond flour on a bed of greens with cucumber and goat cheese

Afternoon Snack: A handful of walnuts with a quarter cup of berries

Dinner: Grilled beef kebabs with peppers and sauteed broccoli

The Bottom Line

When it comes down to it, I wouldn’t recommend a keto diet to most people, and don’t typically recommend it to my clients. However, I have had clients where we employed a “modified keto” approach to weight loss, for those who do well or generally feel better on lower carb diets.

If you are following a keto diet or thinking about starting the keto diet, I encourage you to ask questions. Do the research and seek the advice of your doctor and a Registered Dietitian. No matter what diet you choose to follow, it has to be sustainable.

Lastly, getting to the root of your eating habits and your own internal motivators are paramount to achieving weight loss and keeping it off.

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