Is keto diet safe and effective way to lose weight?

Recently, the keto diet has been gaining popularity among those who want to lose weight, so this time we will figure out whether it is really possible to lose weight with this diet and how good is it for our health according to scientific research.

Is keto diet effective for weight loss?

Several studies suggest that the keto (low carb, high fat) diet can be as effective, if not more effective, than a low fat diet for weight loss [1, 2, 3, 4].

But what if we compare body fat loss on each diet instead of just comparing body weight loss?

And is a calorie really just a calorie? Do we lose the same amount of weight and body fat when eating 800 kcal less of carbohydrates (when on keto diet) and 800 kcal less of fat (when on a low-fat diet)? In other words, how fast can you lose weight on keto and how fast can you lose body fat on keto?

Well, scientific research shows that by the end of the 6 day period cutting about 800 kcal/d on a low-fat diet resulted in 463±37 g of fat loss compared to 245±21 g of fat loss with the low-carb (keto) diet [5].

If we compare the overall body weight loss then you can notice that body weight loss is greater on a low-carb diet than on a low-fat diet. However, on a low-carb (keto) diet you may get a greater amount of lean mass loss such as body water than fat loss [5].

This can be the reason why many people suggest keto diet for weight loss and you may see some studies showing that on a keto diet people lose more body weight faster than on a low-fat diet. It’s simply because keto diet really can help you lose body weight on a scale by losing lean mass like body water but not body fat.

The results of a meta-analysis of 23 clinical studies show that the keto diet is as effective for weight loss as the low-fat diet and that cholesterol levels on the keto diet are not significantly worse than those on the low-fat diet [6]. But cholesterol levels may depend on what kind of keto diet you are following: healthy or unhealthy. Read more about it in the next chapter.

The same meta-analysis mentions that low-carbohydrate diets (like a keto diet) are often high in fat, and high-fat diets have been associated with increased risks of certain types of cancer in some observational studies. Thus, moderating the amount and types of fat substituted for carbohydrates is prudent not only to improve cardiovascular and metabolic risk factors but also to avoid increasing risk for other chronic diseases [6].

Is keto diet safe for our health?

Several studies note that a keto diet raises cholesterol levels and may be harmful to our health in the long term [1, 2,3].

A meta-analyses of carbohydrate intake and mortality shows that both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50-55% carbohydrate intake.

Low carbohydrate dietary patterns favoring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favored plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality [7].

And a study of more than 100,000 participants shows that a low-carbohydrate diet containing animal products increases the risk of all-cause mortality (cardiovascular disease, cancer, etc.), while a low-carbohydrate diet based on the consumption of vegetables, reduces all-cause and cardiovascular disease mortality rates [8].

Also, one study claims that a diet low in carbohydrates, high in fat and protein may increase the risk of developing type 2 diabetes in the long term [9].

At the same time, it is noted that if you reduce the consumption of livestock, poultry, products of their processing and increase the consumption of vegetables, fruits, fiber, then you can improve the condition [9].

One more study shows that keto diet may help treat epilepsy but keto diet side effects include constipation, dyslipidemia, growth slowing, acidosis, and kidney stones [10].


So, is keto diet safe, effective and fast way to lose weight according to scientific research? It depends. In general, the answer is no. Although keto diet can give you some fast body weight loss but it’s mostly lean mass loss like body water loss and not fat loss.

Also, keto diet may create some other health problems, especially in the long term and when eating some unhealthy foods on keto diet.

Do you want to know what is the healthiest diet according to scientific research? Then click here to read my blog article (opens in new tab) on this topic.

P.S. If you want to find out how science-based nutrition and diet can prevent and treat the most common diseases, improve your overall health and help you live longer then you can click here to learn more.

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