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Keto Vs. Fasting for Weight Loss

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  Published on October 23rd, 2023
  Reading time: 4 minutes
  Last modified September 25th, 2023
Intermittent fasting and keto

If you want to slim, trim, and shed the pounds but don’t know where to start, you’re not alone. It’s easy to feel lost in the clutter of weight loss promises, fads, diets, and products. You might have heard that intermittent fasting and a ketogenic diet are beneficial for weight loss. Which is more effective? What’s best for you, your lifestyle, and your goals? Let’s take a look at keto versus fasting for weight loss.

Keto for Weight Loss

It’s no secret that ditching the carbs and sugar and welcoming in the healthy fats works wonders for your waistline. If you keep your carb intake low enough for long enough, your body enters an advantageous metabolic state called ketosis, where your liver breaks down fatty acids and turns them into ketones. It’s not a magic bullet, and it takes time and dedication to follow a healthy, well-formulated ketogenic diet and lose body fat. 

However, evidence is mounting that the ketogenic diet is one of the most effective for weight loss. [1]

Keto is a high-fat, moderate protein diet that keeps you feeling fuller for longer, so you’re less likely to overeat and gorge on unhealthy foods. Studies show some people feel hungrier during the first few weeks of transitioning to a ketogenic diet as their metabolism adjusts, but those who stick with it can lose 10 to 17% of their weight without feeling hungry. [2]

While the immediate weight loss that occurs in the first week or two will largely be water weight, you should continue to lose excess weight at a steady pace. Weight loss tends to peak around the five-month mark.

Insulin resistance cycle

Keto works in part because not all calories are created equal, and different macronutrients and calories affect your body and metabolism differently. When you’re not eating all those carbs and sugar, your blood sugar levels are reduced, and there’s less need for insulin. Insulin is a hormone that stores sugar in your cells and prevents your blood sugar from rising dangerously high. Insulin is also the fat-storage hormone, so it tells your body to hold on to fat. This means that every time you eat sugar, you’re prompting the release of insulin and telling your body to hold on to your fat stores, which inhibits weight loss. On a ketogenic diet, you’re relying on fat as your main energy source and leaving all that sugar in the past. 

A simple way to think about it might be the following equation: less sugar = less insulin = less fat storage.

Lowering your need for insulin shifts your body over from fat-storage mode to fat-burning mode. A reduction in sugar (glucose) levels also sensitizes insulin receptors so they aren’t overwhelmed with the excess surges of insulin. 

Studies reveal a low-carb ketogenic diet works better for long-term weight loss than a low-fat diet. [3] Studies also show ditching sugar and sugar-sweetened beverages helps with weight loss, which is a given on a ketogenic diet because the goal is to keep your daily carb count below around 50 grams of net carbs. [4]

Fasting for Weight Loss

Intermittent fasting involves abstaining from eating during certain time frames. It’s about when you eat rather than what you eat. There are different types of fasting. Some people restrict food intake to 8 hours per day and avoid eating for the remaining 16 hours. Others fast for 24 hours once each week. Still others might try a three-day fast during they only drink water (often with an electrolyte supplement).

Fasting has proven to be advantageous for weight loss for several reasons. Intermittent fasting can decrease inflammation and blood sugar levels, which helps with weight loss.

When you’re fasting, you aren’t consuming calories, and your caloric intake reduces overall. Like the ketogenic diet, fasting also reduces insulin levels and improves insulin sensitivity. [5]

Studies show fasting also increases levels of norepinephrine, which can increase calorie burning and boost metabolism. [6] Your body sends norepinephrine to your fat cells, prompting them to break down body fat into free fatty acids to be used for energy. 

One impressive review revealed that over 3-12 weeks, fasting can reduce body weight by up to 8% and reduce body fat by up to 16%. [7]

Keto Vs. Fasting: What’s Right for You?

Keep in mind you don’t have to choose keto or fasting. There’s a powerful synergy between both a ketogenic diet and intermittent fasting. Research and anecdotal evidence suggests that IF can accelerate ketosis and weight loss. [8] It’s also easier to fast when you’re already in ketosis (because of reduced hunger and cravings) and fat-adapted (because your body is used to burning fat instead of glucose for energy). As a result, you’ll probably find you experience the best weight loss results when you try both of these methods together. Try starting by fasting for 16 hours every day or adding in one day of fasting each week.

Intermittent fasting on keto

Some people handle fasting better than others. The right path for you depends on your health, lifestyle, weight loss goals, preferences, and how fast you want to lose weight. If you have a poor metabolism, you may not be able to handle fasting right away. You may need to work on lowering your carb count and introducing fasting more gradually. On the other hand, if you’re more fat-adapted and you don’t have health problems, you might have an easier transition into fasting and ketosis. 

It will probably take you some time to experiment and figure out what’s best for you. Check out our detailed guide to intermittent fasting for more information and stay on track with your weight loss goals by cooking up some of the delicious keto recipes here on Ketogenic.com.

Steph Green is a content writer specializing in and passionate about healthcare, wellness, and nutrition. Steph has worked with marketing agencies, written medical books for doctors like ‘Untangling the Web of Dysfunction,’ and her poetry book ‘Words that Might Mean Something.’ In 2016, after four years of struggling with her own health problems and painful autoimmune disease, Steph developed a life-changing and extensive knowledge of keto, nutrition, and natural medicine. She continues on her healing journey and enjoys helping others along the way.



Masood, W., Annamaraju, P., Suheb, M. Z. K., & Uppaluri. (2023). Ketogenic Diet. Stat Pearls Publishing. Ketogenic Diet - PubMed (nih.gov)


Nymo, S., Coutinho, S. R., Jorgensen, J., Rehfeld, J. F., Truby, H…Martins, C. (2017). Timeline of changes in appetite during weight loss with a ketogenic diet. International Journal of Obesity, Timeline of changes in appetite during weight loss with a ketogenic diet | International Journal of Obesity (nature.com)


Bueno, N. B., De Melo, I. S., De Oliveira, S. L., & Ataide, T. R. (2013). Very low-carbohydrate ketogenic diet v. low fat diet for long-term weight loss: A meta-analysis of randomised controlled trials. British Journal of Nutrition, Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials | British Journal of Nutrition | Cambridge Core


Liwei, C,. Lawrence, A., Catherine, L., Pao-Hwa, L., Catherine, C. M…Benjamin, C. (2009). Reduction in consumption of sugar-sweetened beverages is associated with weight loss: the PREMIER trial. American Journal of Clinical Nutrition, Reduction in consumption of sugar-sweetened beverages is associated with weight loss: the PREMIER trial - ScienceDirect


Heilbronn, L. K., Smith, S. R., Corby, M. K., Anton, S., & Ravussin, E. (2005). Alternate-day fasting in nonobese subjects: Effects on body weight, body composition, and energy metabolism. The American Journal of Clinical Nutrition, https://doi.org/10.1093/ajcn/81.1.69


Zauner, C., Schneeweiss, B., Kranz, A., Madl, C., Ratheiser, K…Lenz, K. (2000). Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. The American Journal of Clinical Nutrition, https://doi.org/10.1093/ajcn/71.6.1511


Stockman, M-C., Thomas, D., Burke, J., & Apovian, C. M. (2018). Intermittent fasting: Is the wait worth the weight? Current Obesity Reports, Intermittent Fasting: Is the Wait Worth the Weight? | SpringerLink

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