9 Keto Diet Dangers Nutritionists Want You to Know About
Everyone knows someone who’s trying the keto diet, whether it’s Halle Berry or your Uncle Joe. The popular eating plan advises breaking down your daily calories into about 70% fats, 20% protein, and 10% carbs in order to enter a metabolic state called ketosis, where your body burns fat for energy instead of its preferred fuel, carbohydrates.
The diet can prove hard to follow based on sheer restrictiveness alone, but it may also impact your health in other ways besides weight loss. Here’s what you need to know about keto before you ditch healthy whole grains and fruits in the name of New Year’s resolutions.
You’ll likely notice a few key differences during your first days and weeks on the keto diet:
While it’s not necessarily dangerous, bad breath is a known side effect of entering ketosis. When you’re taking in a lot of fat, your liver metabolizes it and eventually converts it into smaller ketone bodies. These ketones (including acetone — yep, like nail polish remover acetone) will circulate in your body and diffuse into your lungs. Your body wants balance, so you’ll exhale ketones to avoid build-up in your bloodstream. Those compounds are what cause keto breath: a metallic-tasting, somewhat stinky side effect.
During your first week of keto, you may experience flu-like symptoms such as aches, cramping, fatigue, diarrhea, constipation, general weakness, and a skin rash. This is actually a side effect of water and electrolyte loss, and is likely indicative of dehydration.
When you turn to fat for fuel, you lose more water and electrolytes in your urine due to a decrease in your body’s insulin levels and a loss of muscle glycogen. (When you’re in ketosis, you’ll use muscle glycogen for energy first.)
Low-carb diets can have a diuretic effect within the first few days in general, but on keto you’re drastically cutting down on foods with the most water and potassium: produce. Anyone who is planning on doing keto long-term will need to drink additional fluids with electrolytes since you’re taking in less overall but expelling more of them.
The lethargy you experience? Research attributes it to your brain not receiving enough glucose. This side effect appears to be brief, but still uncomfortable and unpleasant.
There’s many suggested interventions for these short-term keto side effects on the internet, but know that there are potential pitfalls of these dietary supplements. While there are benefits for some specific cases, many of us will experience nausea, vomiting, diarrhea, and constipation as a result. Plus, unless they’re prescribed to you by a physician, dietary supplements come with their own safety gamble.
Here’s what you might experiences after a few months (or years) on the keto diet:
Beyond the short-term effects of the keto flu, the diet can also negatively impact your digestion and gut in the long run. One 10-year study conducted on using keto to manage pediatric epilepsy found the following GI side effects over time: constipation, high triglyceride levels, high cholesterol, diarrhea, lethargy, iron deficiency, vomiting, and kidney stones.
The processed foods with sugar alcohols allowed on the keto diet also have their own gas, bloating, nausea, diarrhea, and constipation-inducing effects that increase with the amount you eat every day.
Weakened immune system
A number of studies suggest keto can disrupt the balance of good and bad bacteria in your GI tract (a condition called dysbiosis) due to high saturated fat intake and eating less fiber. Diets lacking in prebiotic fiber decrease probiotic, “friendly” bacteria as a result. Since the GI tract is considered the “bodyguard” of your immune system, this may impact your gut-brain connection, immune function, and chronic disease risk.
Vitamin and mineral deficiencies
The research on ketogenic diets also suggests you’ll need to take a multivitamin to get enough minerals, calcium and vitamin D — most of which are readily available in plant-based foods. One keto-specific example: Not getting enough selenium, an immune-boosting antioxidant found in plant foods, can cause cardiomyopathy, a hardening of the heart muscle leading to heart failure.
An even bigger concern from my POV: Dietary supplements aren’t overseen by the FDA, meaning they’re not evaluated for safety and efficacy in the same way that food and medications are — so you may not be getting exactly what you pay for. And if you are? Well, consuming certain nutrients in supplement form versus food form can induce oxidative stress rather than treating it — and cause more harm than good to your organs.
Increased risk of chronic disease
In order to stay in ketosis, you have to limit carbs, but also to some extent protein. This is the predominant difference between keto and traditional lower-carb diets like Atkins. By relying on dietary fat for most of your calories per day, you limit fiber-rich sources (like fruit, veggies, and legumes) and sources of lean protein (like fatty fish) — some of the most nutrient-dense foods on the planet.
Across the globe, diets high in vegetables and fruit are linked to reducing long-term chronic disease risk, including diabetes, heart disease, and lifestyle-related cancers. Data suggests that the more produce we eat, the better off we are. On keto, however, you have to restrict how many net carbs (and therefore, veggies) you’re consuming per day, minimizing their beneficial effects.
The high-fat intake required for ketosis may change the structure of LDL (“bad”) cholesterol and lipoproteins, which could induce inflammation over time. Chronic inflammation is a biological state in which your body’s cells work overtime to get their regular job done. Healthcare professionals can ID inflammation through blood work by looking for signs of oxidative stress (a.k.a. the damage done by free radicals to organ tissues).
This makes keto tough to recommend, since chronic inflammation is linked to heart disease, and 49% of us are already at risk for it.
If you can’t maintain any eating plan forever due to its level of restriction and burden, it can lead to weight cycling — the process by which you gain a lot of weight and lose a lot of weight when “dieting” versus when you’re off of a diet. That can lead to increased chronic disease risk, not to mention how it can make weight loss more difficult the more often you do it.
The ketogenic state in particular can increase the hormones that make you feel full and decrease the hormones that make you feel hungry. Sounds great, right? Well, once you’re off the keto diet, the appetite-suppressing hormones will increase significantly from your baseline. Meaning that you’ll likely feel even hungrier than you did before you started!
The Bottom Line
Any plan that restricts real, whole foods, and requires taking supplements comes at a cost, including financial and environmental ones.
Cutting back on these nutritious foods for weight loss propagates diet myths about what it looks like to eat in a balanced way. That said, weight loss is highly personal and unique to every single one of us. Ultimately, if you can find better health (physical and psychological) on keto, then of course I’d encourage you to stick with it!
But since the data shows me quite the opposite (and since we can’t always rely on “willpower” to keep us in check): Approach weight loss first by considering your lifestyle and shifting toward healthier eating habits through behavior changes that promote physical, mental, and psychological well-being for life.
Always consult with your doctor before starting any weight-loss plan, but if you’re currently taking meds for diabetes management, it is absolutely essential that you talk to your endocrinologist before beginning keto. Some medications actually require eating some carbohydrates to ensure your safety.
For better ways to do lose weight and get healthier without uprooting your entire life, check out our Nutrition Director’s new book, Dressing on the Side (and Other Diet Myths Debunked): 11 Science-Based Ways to Eat More, Stress Less, and Feel Great About Your Body.