{"id":531871,"date":"2026-07-18T06:17:17","date_gmt":"2026-07-18T06:17:17","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/531871\/"},"modified":"2026-07-18T06:17:17","modified_gmt":"2026-07-18T06:17:17","slug":"ketos-dark-side-the-health-risks-behind-rapid-weight-loss","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/531871\/","title":{"rendered":"Keto\u2019s dark side: The health risks behind rapid weight loss"},"content":{"rendered":"

Few diets have become as alluring in recent years as the ketogenic diet. The principle is simple: eat fewer carbohydrates, consume more fat and protein and, in many cases, watch the weight fall off quickly, at least at first.<\/p>\n

For many people, it sounds like a straightforward solution in a confusing world of nutrition. But make no mistake: Behind that promise lies an extreme diet that may carry a significant health cost.<\/p>\n

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Ketogenic diet (keto)<\/p>\n

(Photo: Shutterstock)<\/p>\n

\u201cIn the classic, traditional ketogenic diet, people eat mainly fat and protein and sharply reduce their carbohydrate intake,\u201d explains Dr. Sigal Frishman, head of Nutrition Department at Rabin Medical Center (Beilinson) and chief dietitian of Clalit Health Services\u2019 hospital division.<\/p>\n

\u201cThe body normally uses glucose as its main source of energy. But when people do not consume enough carbohydrates, the body begins breaking down fat, producing ketone bodies in the process. The goal of the keto diet is to maintain a steady level of ketones in the blood so the body uses them for energy instead of glucose.\u201d<\/p>\n

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A simple set of rules: The ketogenic diet<\/p>\n

(Photo: Shutterstock)<\/p>\n

The ketogenic diet, Frishman notes, did not begin as a weight-loss trend. It was originally developed as a therapeutic tool for children with drug-resistant epilepsy. \u201cDoctors found that in children with epilepsy and seizures, the brain could receive energy from ketone bodies rather than glucose, and in some cases the diet could help reduce seizures or even stop them,\u201d she says.<\/p>\n

Over time, however, keto moved beyond its original medical use and began attracting people with excess weight, diabetes or elevated triglyceride levels. The appeal is easy to understand: Sharply reducing carbohydrates can, at least in the short term, improve certain measures related to blood sugar and blood fats.<\/p>\n

\u201cMany people who follow a short-term ketogenic diet lose weight very quickly,\u201d Frishman says. \u201cThere is a very sharp decline in appetite, and when there is no appetite, people lose weight.\u201d <\/p>\n

Beyond its physiological effects, keto also has a powerful psychological appeal because it offers a simple set of rules. \u201cFor many people, a strict, black-and-white regimen is easier to follow than broad dietary guidelines,\u201d Frishman says. \u201cIt is easier to embrace a rule such as: Eat as much meat, chicken, fish, eggs, butter and full-fat cheese as you like, and everything will work out.\u201d<\/p>\n

But that simplicity is also part of the problem. When a diet eliminates a major food group and alters how the body produces energy, it is no longer merely a weight-loss method. It becomes a significant nutritional intervention, and that is where the risks begin.<\/p>\n

The chief concern among experts regarding the ketogenic diet involves a measure that people do not necessarily feel in their bodies or see on the scale: an increase in LDL, commonly known as \u201cbad\u201d cholesterol, which is linked to atherosclerosis and elevated cardiovascular risk.<\/p>\n

Dr. Chen Gurevitz, head of the preventive cardiology center in Rabin Medical Center says the debate surrounding the ketogenic diet is complex. \u201cWhat makes this diet so appealing is the rapid weight loss,\u201d she says. \u201cCutting carbohydrates can also lead to significant improvements in blood sugar levels, diabetes control, triglycerides and fatty liver.\u201d<\/p>\n

But weight loss and improved blood sugar do not tell the whole story. One of the central questions is what happens simultaneously to the blood vessels, and particularly to LDL levels. \u201cLDL is the main driver of atherosclerosis in the body, and there is a direct connection between LDL and heart attacks, strokes and mortality,\u201d Gurevitz says. \u201cWe know from hundreds, if not thousands, of studies that as LDL rises, the risk of cardiovascular disease rises as well.\u201d<\/p>\n

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\u2018What makes this diet so appealing is the rapid weight loss.\u2019 Dr. Chen Gurevitz<\/p>\n

(Photo: Liraz Carmeli)<\/p>\n

According to Gurevitz, the concern is not merely theoretical. In some cases, doctors encounter the consequences directly. \u201cWe have seen quite a few patients arrive at cardiac catheterization laboratories with a heart attack or requiring an urgent catheterization, and they told us that they had begun a ketogenic diet six months or a year earlier,\u201d she says.<\/p>\n

\u201cWhen we examine their LDL levels, we find high and sometimes extreme values. In some cases, these may have been people who already had elevated LDL, then began this diet and sent their LDL soaring. It simply gave another push to the atherosclerosis that blocked their artery.\u201d<\/p>\n

Not everyone who follows a ketogenic diet experiences such a rise. In some people, LDL levels change very little, and some reports have even found a decline. Gurevitz warns, however, that one group can respond far more dramatically. The phenomenon, which has recently drawn growing attention, is known as \u201clean mass hyper-responders.\u201d<\/p>\n

\u201cSome people on a ketogenic diet see little change in their LDL levels, and some reports have even found a decline,\u201d she says. \u201cBut there is another group whose prevalence remains unclear. They are typically not overweight and do not begin the diet with obesity, yet their LDL levels can rise dramatically in response to keto.\u201d<\/p>\n

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For some people, the rise in LDL levels can be dramatic<\/p>\n

(Photo: Shutterstock)<\/p>\n

For some people, the rise in LDL levels can be dramatic, and in such cases, she says, LDL can double or even triple. \u201cWe reach truly extraordinary numbers that were once usually seen only in patients with very rare inherited cholesterol disorders,\u201d Gurevitz says. \u201cIn these patients, both LDL and ApoB, a protein that reflects the number of atherosclerosis-causing cholesterol particles in the blood, rise sharply. Both are known to be major drivers of atherosclerosis.”<\/p>\n

That is also where the uncertainty in the research becomes important. It remains unclear whether the diet\u2019s potential benefits outweigh its possible risks. \u201cIn cardiology, we always follow what is strongly supported by research, and there is not enough research on the ketogenic diet,\u201d Gurevitz says.<\/p>\n

\u201cThere is no evidence that a ketogenic diet is superior to other diets regarded as healthy, such as the Mediterranean diet, which has been shown in numerous studies to be the preferred diet in terms of cardiovascular outcomes.\u201d<\/p>\n

Keto supporters sometimes argue that higher LDL during ketosis is not necessarily dangerous because it results from a unique change in fat metabolism. Gurevitz treats that claim with considerable caution. \u201cThe truth is that we do not have enough information to say that,\u201d she warns. \u201cIt is a very problematic statement and may also be irresponsible.\u201d<\/p>\n

Those who need to be particularly careful, she says, include people who already have high cholesterol, a family predisposition to cholesterol disorders, known atherosclerosis or a tendency to absorb more cholesterol from food. \u201cThese people need to be cautious about a ketogenic diet, and it would be better for them to choose other diets,\u201d she says.<\/p>\n

Beyond cholesterol and cardiovascular risk, another major concern with the ketogenic diet is what it removes from the plate. Cutting carbohydrates sharply may eliminate not only sugar, sweets and processed foods, but also nutrient-rich foods that play an important role in a balanced diet.<\/p>\n

\u201cWe know how important fiber is,\u201d Frishman says. \u201cIt is found in foods such as whole grains, vegetables and fruit. Different fruits and vegetables provide different types of fiber, while their colors and polyphenols supply valuable antioxidants, along with a wide range of vitamins.\u201d<\/p>\n

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\u2018The problem is not only what people eat, but also what they stop eating.\u2019 Dr. Sigal Frishman<\/p>\n

(Photo: Rami Zarnegar)<\/p>\n

In strict versions of keto, she says, many of the foods that provide those nutrients are almost entirely removed. \u201cThere are almost no vegetables, no grains and no legumes, which are also an important source of fiber,\u201d Frishman says. \u201cPeople barely touch these foods.\u201d<\/p>\n

\u201cThe purpose of fiber is first of all to increase the diversity and quantity of the bacteria in our intestines. Those bacteria produce metabolites that protect the body, improve the immune system, maintain a healthy intestine and are also linked to protection from disease.\u201d<\/p>\n

The effect of reduced fiber intake is not limited to constipation, although that is among the more common and immediate consequences. According to Frishman, a major reduction in fiber may also affect the microbiome, the population of bacteria in the intestines, and impair the gut\u2019s function as a barrier between the digestive system and the bloodstream.<\/p>\n

\u201cIt can lead to a smaller quantity and variety of intestinal bacteria, with potential consequences for the immune system and the body\u2019s defenses,\u201d she says. \u201cIntestinal permeability may also increase. The intestine is a line of defense between the food we eat and the blood. Food must be broken down, and substances that we want to enter the bloodstream need to pass through. But there are also substances we do not want entering the blood because they may activate systems we do not want activated.\u201d<\/p>\n

\u201cWhen we do not eat enough fiber, we do not have enough of the bacteria that help keep the intestine from becoming overly permeable.\u201d<\/p>\n

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\u2018Strict keto diets contain few fiber-rich foods such as grains, legumes, fruits and vegetables<\/p>\n

(Photo: Shutterstock)<\/p>\n

Low fiber intake has also been linked to an increased risk of intestinal diseases, particularly colorectal cancer. \u201cA classic ketogenic diet sometimes also includes a large amount of saturated fat, which has also been linked to a higher risk of certain diseases,\u201d Frishman says.<\/p>\n

In other words, the problem is not only what people eat, but also what they stop eating. A diet based mainly on fat and protein may provide fewer fibers, fewer plant-based components and less diversity, all of which are essential to a diet that promotes long-term health.<\/p>\n

Beyond cholesterol, heart health and nutritional quality, the ketogenic diet has several other weaknesses that are important to recognize, particularly among people who already have underlying health conditions or a predisposition to certain disorders.<\/p>\n

One is the risk of kidney stones and elevated uric acid. \u201cIn principle, a ketogenic diet increases acidity, and failing to drink enough can raise the risk of kidney stones,\u201d Frishman explains. \u201cSome people consume significantly more animal-based foods, and animal proteins contribute to acidity. It is therefore important to drink plenty of water to regulate and reduce that acidity, which naturally lowers the risk.\u201d<\/p>\n

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\u2018A ketogenic diet increases acidity, and failing to drink enough can raise the risk of kidney stones’ <\/p>\n

(Photo: Shutterstock)<\/p>\n

Another concern involves uric acid, a byproduct of the breakdown of purines, which are found in relatively high amounts in animal-based foods. \u201cWhen uric acid levels rise in the blood, it can accumulate in the joints and cause gout, which is characterized by pain and sometimes acute joint inflammation,\u201d Frishman says.<\/p>\n

People with diabetes should be especially cautious when considering a ketogenic diet. \u201cWhen carbohydrate intake is eliminated, blood sugar levels fall,\u201d Frishman explains. \u201cBecause some diabetes medications also lower blood sugar, combining the two can lead to hypoglycemia, a dangerously low blood sugar level. People taking glucose-lowering medication should therefore not begin the diet without closely monitoring their blood sugar.\u201d<\/p>\n

A strict ketogenic diet is also unsuitable for certain groups without close medical supervision. \u201cPregnant women should certainly avoid it,\u201d Frishman stresses. \u201cChildren should not follow it without medical oversight either.\u201d<\/p>\n

Even people without underlying health conditions may face a simpler but equally important problem: Keto is extremely difficult to sustain over time. Severely restricting carbohydrates, avoiding everyday foods and living with a constant sense of deprivation can make the diet unmanageable for many people.<\/p>\n

\u201cThat can lead to a significant rebound because most people find it very difficult to live without carbohydrates,\u201d Frishman says. \u201cMost studies show that after a year, many return to eating even less healthfully than before because of the prolonged restriction.\u201d<\/p>\n

Does that mean the ketogenic diet should be ruled out altogether? Not necessarily. Here too, the experts say, the details matter. \u201cI would not dismiss it entirely,\u201d Frishman says. \u201cIt can be modified. For some people, it may provide the clear initial framework they need because a black-and-white approach is easier to follow. But I would choose a more Mediterranean-based approach, perhaps one that is less strict than full keto, while monitoring blood tests and the results.\u201d<\/p>\n

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Decided to try keto? Make sure to get regular blood tests<\/p>\n

(Photo: Shutterstock)<\/p>\n

Some people now follow modified versions of keto built around healthier fats such as tahini, olive oil, avocado and olives rather than saturated fat, while also choosing leaner protein sources, including chicken, fish and lower-fat cheeses.<\/p>\n

\u201cOnce they have achieved results, changed their habits and established a healthier routine, the goal should be to gradually transition away from such a restrictive regimen toward a more balanced and sustainable diet,\u201d she says.<\/p>\n

Even for those who decide to try keto, the cardiological advice is clear: Do not proceed without monitoring. Gurevitz stresses that blood lipid levels should be checked soon after starting the diet, rather than relying solely on weight loss or improved blood sugar readings.<\/p>\n

\u201cPeople need to pay very close attention to their blood tests,\u201d she says. \u201cThey should conduct careful monitoring and even undergo blood tests several weeks into the diet to see what is happening to their lipid profile, specifically LDL cholesterol, and determine how their body is responding.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Few diets have become as alluring in recent years as the ketogenic diet. The principle is simple: eat…\n","protected":false},"author":2,"featured_media":531872,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[36],"tags":[134,111,139,556,69],"class_list":["post-531871","post","type-post","status-publish","format-standard","has-post-thumbnail","category-nutrition","tag-health","tag-new-zealand","tag-newzealand","tag-nutrition","tag-nz"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/531871","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=531871"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/531871\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/531872"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=531871"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=531871"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=531871"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}