The keto and paleo diets have gained immense popularity recently, but are they truly beneficial for your health? Experts advise exercising caution.
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Emerging research has cast doubt on the popular paleo and keto diets, which emphasize high protein and low carbohydrate intake. While these dietary approaches have garnered a loyal following due to their short-term weight loss success, experts and recent studies are uncovering troubling health risks associated with their restrictive nature.
The ascent and potential dangers of the Keto diet
The keto diet originated in the 1920s as a therapeutic tool for managing epilepsy, according to the National Library of Medicine. By severely limiting carbohydrates—often to fewer than 50 grams per day—keto forces the body into a metabolic state known as ketosis, where fat is burned instead of glucose for energy. While this can yield dramatic short-term weight loss, emerging evidence suggests significant long-term risks.
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A study published in the journal Frontiers in Nutrition analyzed more than 100 peer-reviewed papers on the keto diet and concluded that “the ketogenic diet is especially unsafe for pregnant women and people with kidney disease and may increase chronic disease risk for the general population.” The study linked the diet to elevated levels of low-density lipoprotein (LDL) cholesterol—commonly known as “bad” cholesterol—and an increased risk of cardiovascular disease, cancer, diabetes, and Alzheimer’s disease.
Vanessa Rissetto, a licensed dietitian and co-founder of the nutrition firm Culina Health, highlights the dangers linked to limiting carbohydrate intake.
“Carbohydrates serve as the primary energy source for our bodies,” she explained to Fortune. “Those following a keto diet may find themselves deficient in fiber, minerals, and micronutrients, which can adversely affect gut health, sleep quality, and energy levels. Additionally, the increased intake of red meat associated with this diet is concerning, as it has been directly linked to colon cancer and various other health problems.”
The Cleveland Clinic highlights various negative impacts associated with the keto diet, such as nutrient deficiencies, strain on the liver, kidney issues, constipation, and cognitive fog. Although supporters claim that ketosis provides metabolic advantages, the diet's heavy dependence on saturated fats has faced scrutiny due to its possible detrimental effects on heart health.
The debated foundation of the paleo diet
The paleo diet’s guiding philosophy stems from the idea that modern health issues result from the mismatch between contemporary diets and the foods consumed by our Paleolithic ancestors. Popularized by Loren Cordain’s 2001 book The Paleo Diet, like the keto diet, the approach emphasizes whole foods like lean meats, fish, fruits, vegetables, nuts, and seeds while excluding grains, legumes, dairy, and processed foods.
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Nonetheless, some critics contend that the historical validity of the diet is questionable and that its health benefits are exaggerated. "Achieving a genuine Paleolithic diet is unfeasible since the nature of food has evolved significantly—thanks to advancements in food processing, agricultural practices, and the evolution of plant species," remarked Federica Amati, a nutrition scientist affiliated with the health science company Zoe.
A study published in the journal Nutrients found that individuals following a paleo diet had higher levels of a blood biomarker associated with cardiovascular disease. While some studies have observed short-term benefits, such as weight loss and improved glucose control, long-term adherence to the diet raises concerns about nutrient deficiencies, particularly in calcium and vitamin D due to the exclusion of dairy products.
Evaluating the two dietary approaches
While keto and paleo have distinct origins and guidelines, they both revolve around high-protein, low-carbohydrate principles. The ketogenic diet prioritizes specific macronutrient ratios, aiming for 60% of daily caloric intake from fats, 30% from protein, and only 10% from carbohydrates, as noted by the Cleveland Clinic. On the other hand, the paleo diet emphasizes the elimination of processed foods and agricultural items, including grains and legumes.
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The similarity in carbohydrate limitation between these diets contradicts the US Dietary Guidelines, which suggest that 45 to 65 percent of daily caloric intake should come from carbohydrates. Opponents of these diets argue that reducing carbohydrate intake—a key source of energy—might result in negative health effects, such as tiredness, digestive problems, and compromised gut health.
Recent studies on plant-derived proteins
Adding to the critique of keto and paleo diets, a recent study published in The American Journal of Clinical Nutrition examined the relationship between plant-based and animal-based protein intake and cardiovascular disease. Researchers analyzed data from three large prospective cohort studies: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-Up Study, which collectively included over 200,000 participants.
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The research indicated that a greater ratio of plant protein to animal protein was linked to a notably reduced risk of cardiovascular diseases and coronary heart disease. In particular, substituting merely 3 percent of energy derived from animal protein with plant protein led to an 18-percent decrease in the risk of cardiovascular disease and a 24-percent reduction in the risk of coronary heart disease. Nonetheless, the study did not find any significant effect on the risk of stroke.
Over the course of the 30-year follow-up in the study, the median ratio of plant to animal protein rose from 0.36 to 0.50, indicating a gradual transition towards a plant-centric diet. Although the ideal ratio for reducing the risk of cardiovascular disease is still not clearly defined, the findings highlight the advantages of including a greater proportion of plant-based proteins in one’s diet.
Considerations regarding the environment and ethics
In addition to their effects on personal health, both the keto and paleo diets face scrutiny for their environmental implications. These diets predominantly depend on animal-derived foods, which contribute to increased greenhouse gas emissions, greater water consumption, and more extensive land degradation when compared to plant-centric eating patterns.
Amati emphasizes these issues, remarking, “They have a detrimental impact on the environment and are quite unsustainable.”
Research conducted by the University of Oxford backs this viewpoint, revealing that transitioning from diets centered on animal products to those focused on plant-based options could lead to a decrease in food-related greenhouse gas emissions by as much as 73 percent. This finding is in harmony with the increasing trend towards sustainable eating habits, which emphasize the importance of both individual health and the health of our planet.
Professional suggestions
Healthcare experts are progressively promoting the importance of diverse and balanced diets rather than restrictive methods such as keto and paleo. Amati stated, “To maintain good health, it's essential to include a range of food groups. A personalized nutrition strategy is necessary for everyone.”
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Rissetto shares a similar perspective, highlighting the significance of moderation and incremental changes in one’s diet. She suggests, “Consult with a dietitian who can guide you through the process and help you achieve long-term health and sustainability in your eating habits.”
Instead of rigid dietary rules, experts recommend focusing on plant-forward eating patterns, which emphasize whole grains, legumes, fruits, vegetables, and healthy fats. Such diets are supported by extensive research, including studies linking the Mediterranean diet to reduced risks of heart disease, diabetes, and other chronic conditions.
