A major negative side effect of the keto diet is the short-term "keto flu," with symptoms like headache, fatigue, brain fog, and irritability as the body adapts. Long-term risks can include nutrient deficiencies, digestive issues like constipation (due to low fiber), bad breath, potential kidney problems (like kidney stones from increased acidity and dehydration), and higher cardiovascular risk from high saturated fat intake, requiring careful food choices.
The keto diet could cause low blood pressure, kidney stones, constipation, nutrient deficiencies and an increased risk of heart disease.
Keto diet risks
Top of the list: it's high in saturated fat. McManus recommends that you keep saturated fats to no more than 7% of your daily calories because of the link to heart disease. And indeed, the keto diet is associated with an increase in "bad" LDL cholesterol, which is also linked to heart disease.
Cardiologists generally view the ketogenic diet with caution, noting potential short-term benefits like weight loss and improved blood sugar, but highlighting significant long-term risks, including elevated "bad" LDL cholesterol, potential nutrient deficiencies, and a possible increased risk for heart events like heart attacks, strokes, and angina, making it unsustainable and potentially unsafe for many heart patients compared to more balanced, whole-food approaches.
Diarrhea: The keto diet also typically encourages a high fat intake. Eating a lot of fatty foods can take its toll on your digestion. If your body can't tolerate a high-fat diet, you could develop diarrhea. Abdominal pain: A high-fat, low-fiber diet may also cause gas and bloating.
Other symptoms of ketosis may include:
The rate of weight loss on the keto diet without exercise ranges from 1-2 pounds per week. Therefore, if you want to lose significant weight, reaching your goals may take a few months. Exercise is essential to any weight loss plan, as it helps burn calories, build muscle, and improve overall health.
Not watching your carb intake - Sugar and refined carbs are in many foods. You should be aiming to eliminate these from your keto diet. “Try to keep your net carb content under 20 grams/day or total carbs under 30 grams,” Dr Riggs says. Keep close track of your sugar and carb intake by reading nutrition labels.
Increased risk of heart disease and diabetes. Followers of the keto diet are encouraged to eat quality proteins, non-starchy vegetables, and fruits, and to go heavy on fats. Placing a high emphasis on fat consumption could increase your risk of developing heart disease and diabetes.
The worst carbs for belly fat are refined carbohydrates and added sugars, found in sugary drinks, white bread, pastries, and processed snacks, because they spike blood sugar and insulin, leading to increased fat storage, especially around the abdomen. While no single carb is solely responsible, these quickly digested, low-fiber options promote inflammation and insulin resistance, contributing to visceral (belly) fat.
The 9 core rules of the keto diet focus on drastically cutting carbs (under 20-50g/day) and replacing them with fat (70-80% of calories), while keeping protein moderate (20-25%) to induce ketosis, a fat-burning state. Key rules include eating healthy fats, lean proteins, non-starchy veggies, staying hydrated, avoiding sugar/grains/starchy foods, tracking macros, and potentially incorporating intermittent fasting.
High-fat, low-carb regimen stresses out cells in heart, kidneys, brain, and liver, but effects may be reversible. Many influencers, athletes, and regular folks swear by ketogenic diets—skimping on carbs and feasting on fats to quickly shed pounds and improve their metabolism.
Gulotta recommends staying on keto for six months max before reintroducing more carbs to your diet. And Scott Keatley, RDN, of Keatley Medical Nutrition Therapy in New York City, agrees: “The science hasn't gotten to the point where I would be comfortable recommending it as a forever diet,” he says.
Ketosis doesn't change the natural color of urine much, but dehydration (common in ketosis) makes it darker, like amber or dark orange; however, you test for ketones using strips that change from beige to pink, purple, or brown, indicating "negative," "trace," "small," "moderate," or "large" amounts, showing you're producing ketones. The deeper the color on the strip (dark purple/brown), the more ketones are present, though strips measure acetoacetate, not the main ketone, so blood tests are more accurate, especially for high levels.
A 7 day gut reset may involve eliminating processed foods, sugar, and other potential food triggers, and consuming a diet that is rich in whole foods, fiber, probiotics, and prebiotics.
Your first week delivers the most dramatic scale changes, but here's the reality check—most of this initial loss is water weight, not fat. This is also widely regarded as the hardest week of your keto journey. When you slash carbs, your body depletes glycogen stores in muscles and liver.
Yes, a 16-hour fast should put you in ketosis. However, different people have different experiences. In addition, not everyone should combine methods to reach ketosis. People can reach ketosis after two to four days once they start to eat fewer carbs (around 20 to 50 grams daily).
Low-carb options like berries, avocado, tomatoes, olives, and coconut offer the nutritional benefits of fruits without impacting ketosis. Conversely, high-sugar fruits like bananas, grapes, pineapple, mango, and apples should be avoided as they can impede progress on a keto diet.
On the first 3 days of keto, your body depletes its glycogen (stored sugar) and starts entering ketosis, leading to the "keto flu" with symptoms like headaches, fatigue, brain fog, irritability, and nausea, alongside increased thirst, urination, and rapid weight loss from water loss. This is your body transitioning from burning carbs to burning fat for fuel, a challenging but temporary phase as it adapts.
However, it has been reported that keto diet weight loss can cause more belly fat loss than a standard low-fat diet. One study found that people following a very low-carbohydrate ketogenic diet lost more fat in the trunk area than those following a low-fat diet.
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