Paleo Diet Side Effects and How to Avoid Them

Common Paleo Diet Side Effects and Fixes

The Paleo diet (or “caveman diet”) focuses on whole, unprocessed foods – lean meats, fish, eggs, fruits, vegetables, nuts and seeds – while cutting out grains, legumes, dairy, added sugars and refined oils. It’s popular for weight loss and health, but any major diet change can bring short-term side effects. Understanding these effects helps you avoid feeling frustrated or ill. By planning well and listening to your body, you can ease the transition into a Paleo lifestyle.

Paleo Diet

Common Paleo Diet Side Effects

When you start Paleo, you may notice digestive and energy changes. Common initial side effects include:

Digestive changes: Some people get diarrhea or looser stools when first upping their fiber (from lots of veggies, nuts, and fruits). Conversely, others may get constipated if they cut too many carbs and don’t eat enough Paleo-friendly fiber like leafy greens and starchy vegetables. In either case, bowel habits can change until your gut adapts.
Low-carb flu: Often called the “Paleo flu,” symptoms like headaches, fatigue, weakness, brain fog, or irritability can appear as your body shifts from burning carbs to fat. This usually lasts a few days to a couple of weeks as you adapt.
Blood sugar swings: If you take glucose‑lowering medications (for diabetes), reducing carbs can drop your blood sugar too low (hypoglycemia). Anyone on insulin or certain pills should check with a doctor before cutting carbs.
Cravings and mood changes: Removing sweets and grains can trigger strong carb cravings and low mood for a while. This is normal as your body adjusts. Many beginners report sudden hunger or thinking of bread/pasta frequently.
Bad breath: As you burn more fat, your body may produce ketones (like acetone) that make your breath taste/smell sweet or metallic. Staying hydrated, chewing sugar-free gum, or brushing often usually helps.
Nutrient gaps: Because Paleo cuts out dairy, grains and legumes (common sources of calcium, vitamin D, B-vitamins, iodine, etc.), you might feel extra tired or notice weak nails/bones if not careful. It’s a good idea to include alternative sources of these nutrients (see below).

Most of these side effects are temporary and can be minimized with care. Below, we’ll explain why they happen and how to avoid them.

Why These Side Effects Happen

Understanding the cause helps you address each issue:

Carbs & fiber shifts: Paleo often means big changes in carbohydrates and fiber. If your old diet was high in grains and starches, cutting them can drastically lower your carb intake. Low carbs cause the “keto flu” (headaches, fatigue) as your body burns through glycogen and adjusts. On the flip side, if you suddenly eat a lot more raw veggies and nuts, your fiber intake might spike, and that can lead to loose stools or diarrhea. If you didn’t plan to replace carbs well, low fiber can cause constipation.
Electrolyte changes: When carbs fall, your body flushes out extra water and sodium. This can cause lightheadedness or muscle cramps (symptoms of “low-carb flu”). Drinking extra fluids and adding salt (or broth) can often prevent these symptoms.
Nutrient cutouts: Paleo excludes grains, legumes, and (often) dairy – all rich in certain nutrients. For example, whole grains and legumes provide fiber, B vitamins, and iron; dairy provides calcium and vitamin D. Without them, your diet may be low in fiber, vitamin D, calcium, iron, iodine, thiamin, and riboflavin. Low calcium or D can, over time, affect bone health. Low B vitamins may make you feel tired or weak. This is why beginners sometimes feel lethargic, not just from low carbs but from shifting nutrient balance.
High protein/fat load: Paleo is typically high in protein and healthy fats. If you overdo fatty red meats or eggs, some people notice digestive upset (especially if they have sensitive bowels or IBS). Also, new research suggests very strict Paleo eaters can develop higher levels of certain gut bacteria (like Hungatella) that produce trimethylamine N-oxide (TMAO) from animal foods. TMAO is linked to heart/kidney risks, and Paleo followers had higher TMAO in one study. The culprit may be the lack of fiber-rich resistant starch (found in grains/legumes) that normally fuels beneficial gut bacteria. In short, a meat-heavy Paleo diet long-term could alter gut flora and health.
Blood sugar changes: Cutting carbs improves blood sugar control for most, but if you’re on medication (like insulin or sulfonylureas), this can cause hypoglycemia (low blood sugar). That’s why doctors recommend medical supervision for diabetics starting Paleo or any low-carb diet.

In summary, many side effects stem from sudden changes – carbs, fiber, sugars, and calories – plus nutrient gaps from eliminated food groups. Now let’s see how to prevent or fix these issues.

Practical Tips to Avoid Paleo Diet Side Effects

Many “caveman” complaints can be prevented or eased. Try these practical strategies:

Go gradual: Don’t switch overnight. For example, first replace obvious junk foods (chips, candy) with whole foods. Then cut out grains like wheat. Next, reduce dairy and legumes. This step-by-step approach gives your body time to adapt. You might start with Paleo breakfasts or lunches only, then extend.
Keep plenty of Paleo-friendly carbs: To prevent fatigue and constipation, include starchy vegetables and fruits daily. Sweet potatoes, squash, carrots, bananas and other fruit provide energy and fiber. In fact, Paleo doesn’t have to be ultra-low-carb – feel free to snack on fruit or a baked sweet potato to keep energy up. If you feel weak or your workouts suffer, you may simply need more carbs.
Stay well-hydrated with salt: Low-carb diets have a diuretic effect, so drink more water than usual. Adding a pinch of salt to meals or sipping broth/electrolyte drinks can prevent dizziness, headaches, and muscle cramps. This eases the infamous “low-carb flu.”
Load up on veggies and other fiber: To avoid diarrhea or constipation, eat a variety of vegetables, fruits, nuts and seeds. If diarrhea occurs, you might be overdoing certain fiber (like too many raw cruciferous veggies or nuts). Try cooking or blending vegetables, and drink water with each meal. If constipation happens, ensure you’re drinking enough water and maybe add magnesium-rich foods (avocado, leafy greens). Psyllium husk or chia seeds (Paleo-friendly) can also help regularity.
Eat balanced meals: Combine protein, fat and fiber in each meal to stay satisfied and avoid sugar cravings. For example, salmon + avocado + salad, or chicken + olive oil + steamed broccoli. This combo of nutrients keeps blood sugar steady and wards off “hanger.”
Prepare healthy snacks: Keep boiled eggs, nuts (avoid peanuts if allergic), guacamole with veggie sticks, or fruit handy. Having Paleo-friendly snacks prevents reaching for non-Paleo comfort foods when cravings strike.
Consider a flexible Paleo: Strict Paleo can be hard. Some experts recommend the 80/20 rule – follow Paleo 80% of the time, but allow some flexibility the other 20%. For example, enjoy a small serving of rice or cheese occasionally if it makes meals easier and keeps you on track overall. Paleo “treats” (like dark chocolate or coconut pancakes) can curb cravings without derailing your plan.
Watch nutrients: If you omit dairy, boost calcium through leafy greens (kale, collards), bone-in fish (sardines), or fortified nut milks. Consider a vitamin D3 supplement in winter or if you have low levels. A daily multivitamin can cover any small gaps in B vitamins or iodine. Regularly include iron-rich foods (red meat, liver, spinach) if you feel tired.
Cook at home: Homemade Paleo meals let you control ingredients (no hidden sugars or oils) and ensure variety. Try new recipes (zucchini noodles, cauliflower rice, coconut flour baking) to keep food exciting. Cooking also helps you get used to new foods, reducing shock to the system.
Seek support: Join Paleo forums or local groups. Exchanging tips and recipes with others can help you stick with it. Having a friend join your “caveman journey” or swapping meals can keep motivation high.
Consult a professional: If you have health conditions (diabetes, kidney disease, etc.), talk to a doctor or dietitian before (or soon after) starting Paleo. They can advise on medication adjustments and nutrient monitoring to keep you safe.

By planning meals, eating a variety of Paleo foods, and not rushing, most unpleasant side effects can be prevented or greatly reduced.

Transitioning Smoothly into the Paleo Diet

Think of Paleo as a lifestyle shift rather than an overnight fix. Here are the steps for a smooth transition:

Step-by-step elimination: Follow the advice of Paleo experts: first cut out processed foods (sodas, chips, sweets). Next remove refined sugar and gluten (white flour, pastries). Finally eliminate grains, beans and (if you choose) dairy. This gradual removing of habits helps lessen cravings and digestive shock.
Add before subtracting: It can help to add Paleo staples before deleting old ones. For example, start by adding an extra salad or an egg breakfast each day. As you feel comfortable, you can remove some pasta or cereal later. Eating more of the good stuff often naturally crowds out the bad stuff.
Embrace Paleo swaps: Find replacements for your favorites. Cauliflower rice, zucchini noodles, almond flour muffins, and coconut milk smoothies can satisfy cravings for grains or dairy. These swaps make the change fun and sustainable.
Use the 80/20 rule: As mentioned, allow some flexibility. If you really miss dairy or whole grains, you might reintroduce small amounts of cheese or white rice when dining out.
Learn to cook and plan: Since Paleo cuts many convenience foods, cooking becomes key. Look up simple Paleo recipes (omelets, stews, sheet-pan meals) and prep ingredients on weekends. Planning removes last-minute stress and unhealthy choices.
Experiment and personalize: There is no “one perfect Paleo plate.” Some people do well with more fat, others with more carbs. Pay attention to how different foods make you feel. The Paleo lifestyle is about feeling your best – if something doesn’t feel good (even if it’s Paleo-approved), swap it out.
Stay patient and motivated: Give your body a few weeks to adjust. The first week might be challenging, but many people notice increased energy and reduced cravings soon after. Remind yourself why you began (health, energy, weight loss) and celebrate small wins (like cooking a delicious new dish or exercising more easily).

By easing into Paleo and being flexible, you’ll avoid a sense of deprivation. Remember: eating real, nutrient-dense foods should feel empowering, not punishing.

Listening to Your Body and Making Adjustments

Every person’s “ideal” Paleo diet looks a bit different. After the initial transition, keep tuning in to your body:

Tune into hunger and energy: Eat when you’re hungry and stop when satisfied. Don’t obsess over calories or macros – Paleo naturally balances your meals. If you feel hungry all the time, you may need bigger portions or more snacks. If you feel sluggish or fatigued, you might need more carbs or better sleep.
Adjust macros if needed: Although Paleo is naturally lower in carbs, ensure you’re getting enough energy. Athletes or very active people may need extra sweet potatoes, fruit, or even some starchy plants like white potatoes or rice (if reintroduced). Conversely, if weight loss stalls, consider slightly cutting back on high-calorie Paleo foods (like nuts, oils, or fatty meats).
Watch symptoms: Keep a simple food diary or mental notes. If headaches, energy dips, or stomach issues persist beyond a couple weeks, review what you’re eating. For example, too much nut butter or too little salt? Maybe try a different meat or more vegetables. Small tweaks can solve most issues.
Be your own “caveman”: As one paleo guide says, “Find what works for you”. Some strict Paleo followers do include 1–2 rice meals per week or grass-fed butter without problems. If bacon gives you heartburn, switch to turkey sausage. Personalization is key.
Don’t ignore warning signs: If you ever feel dizzy, faint, or have extreme digestive pain, stop and check in with a healthcare provider. Take “big picture” notes too: are you getting stronger, sleeping well, feeling mentally sharp? That’s a good sign, Paleo is suiting you.
Reevaluate after a few weeks: After about a month, many people reintroduce a few non-Paleo foods to see if anything truly bothers them. For instance, try a glass of milk or a slice of whole-grain bread on separate occasions. This “food challenge” can tell you if certain foods actually cause issues (bloating, energy crash, etc.).
Maintain balance: Paleo is about health, not perfection. Dr. Axe reminds us: “Eat when you feel hungry, and don’t worry about counting calories… listen to your body”. If you’re generally feeling great – good sleep, good mood, stable energy – you likely have the balance right.

Conclusion

The Paleo diet can be a healthy, rewarding way to eat – but it’s a big change from modern diets. By knowing what side effects might occur and why, you’ll be prepared to handle them. Eat plenty of Paleo-friendly fruits and veggies, stay hydrated, and transition gradually. Be patient: most “caveman” cramps and brain fog fade after the first few weeks.

Above all, listen to your body. Adjust portions or food choices if something feels off. The goal is improved health, not perfection. With smart planning and flexibility (even allowing the occasional rice or treat), you can confidently enjoy the Paleo lifestyle and all its benefits. Good luck on your Paleo journey!

FAQs

Will I get sick when starting Paleo?

Not “sick” like a virus, but many people experience mild symptoms (headache, fatigue, moodiness) during the first 1–2 weeks. This is your body adjusting to fewer carbs and more protein/fat. It’s similar to the “keto flu.” The best approach is to hydrate well, eat balanced Paleo meals, and rest. Most people feel normal again after a short adaptation period.

I’m constipated on Paleo – is that normal?

It can happen if your new Paleo plan is low in fiber or you’re not drinking enough water. Make sure you eat plenty of vegetables, fruits, and nuts (Paleo-friendly fiber). If needed, add extra leafy greens or a spoonful of ground flaxseed. Also, drink an extra glass of water or herbal tea each day. These changes usually ease constipation.

How long do these side effects last?

Generally, any side effects are temporary. “Low-carb flu” type symptoms often fade in 7–14 days as your body adapts. Digestive changes usually balance out after a few weeks, too. If a problem (like extreme fatigue or digestive pain) lasts more than a month, recheck your diet for imbalances or consult a professional.

Can I get enough nutrients on Paleo?

Yes, if you plan it well. Eat a wide variety of vegetables, fruits and meats to cover most vitamins and minerals. Be aware that Paleo might miss calcium and vitamin D found in dairy and grains. Broccoli, kale, canned salmon with bones, almonds, and oranges are all good sources of calcium. Sunlight and fatty fish provide vitamin D, though supplements are often needed during the winter months. The UC Davis nutrition team notes Paleo can be low in calcium, iron and some B-vitamins, so a basic multivitamin can be a good safety net.

Is the Paleo Diet very low-carb, like keto?

Paleo isn’t inherently keto. You can include moderate carbs (sweet potatoes, fruit) on Paleo. In fact, carbs from vegetables and fruits are encouraged. If you feel weak, add more carb-rich veggies. If weight loss stalls, you could trim some nuts or oils. Paleo flexibility allows you to dial carbs up or down based on your needs.

I have diabetes/high blood pressure – can I do Paleo?

Paleo often improves blood sugar and blood pressure, but consult your doctor first. If you take diabetes meds, your doses may need to be lowered to avoid hypoglycemia. If on blood pressure pills, be cautious as sodium and fluid changes on Paleo can affect blood pressure too. A healthcare pro can guide a safe switch