By Paleo Life Coach Editorial Team · Last updated September 30, 2026 · Checked against Harvard T.H. Chan School of Public Health and the original trials
Most articles about paleo pick a side. Fans list twenty benefits, critics call it a fad, and neither shows you numbers. This page weighs the paleo diet pros and cons using the controlled trials that exist: what improved, by how much, for how long, and what went wrong for the people in those studies. If you’re deciding whether to try it, or wondering why a friend quit after a few months, you’ll find the trade-offs laid out plainly here.
The quick version: Paleo’s main pros are real but short-term: in trials it cut waist size, triglycerides and blood pressure more than standard diets over about six months. Its cons are higher grocery costs, low calcium and iodine without planning, less gut-friendly fiber, digestive upset early on, and weight-loss advantages that mostly disappear by two years.
Paleo diet pros and cons at a glance
The table below puts every major pro and con next to the evidence behind it. “Short-term” means six months or less, which is where most paleo research stops.
| Pro or con | What the research measured | Trial length | Source |
|---|---|---|---|
| Pro: smaller waist | 2.38 cm more waist loss than guideline diets (pooled, 4 trials, 159 people) | Up to 6 months | Manheimer 2015 meta-analysis |
| Pro: lower triglycerides | 0.40 mmol/L greater drop than control diets | Up to 6 months | Manheimer 2015 |
| Pro: better blood sugar in type 2 diabetes | HbA1c 0.4 percentage points lower than a diabetes diet (13 people) | 3 months per diet | Jönsson 2009 |
| Pro: less junk food | Fewer discretionary items per day than the national-guideline group | 4 weeks | Genoni 2016 |
| Con: higher grocery costs | 69% of paleo eaters vs 6% of controls reported higher costs | 4 weeks | Genoni 2016 |
| Con: digestive upset | Diarrhea reported by 23% of paleo eaters vs 0% of controls | 4 weeks | Genoni 2016 |
| Con: iodine drop | Urinary iodine fell from 134 to 77 µg/day; unchanged in controls | 6 months | Manousou 2018 |
| Con: less resistant starch, higher TMAO | 2.62 g/day (strict) and 1.26 g/day (partial paleo) vs 4.48 g/day in controls; TMAO higher in strict followers | Followers of 1+ year | Genoni 2020 |
| Con: advantage fades | Extra fat loss significant at 6 months, not at 24 months | 2 years | Mellberg 2014 |
Sources: study links are in the sections below and in the Sources list. Effect sizes are as reported in each PubMed abstract.
Two patterns stand out. The benefits are measured in short trials with small groups. The costs show up in daily life: money, digestion, and nutrients you stop getting when you drop whole food groups.
What are the real benefits of the paleo diet?
Paleo’s proven upside is a short-term improvement in the markers doctors use to track metabolic health. A 2015 systematic review in the American Journal of Clinical Nutrition pooled four randomized trials and found paleo beat guideline-based control diets on waist circumference, triglycerides, blood pressure and HDL cholesterol over about six months (Manheimer et al., 2015). The authors rated the evidence quality as moderate.
For people with type 2 diabetes, a small Swedish crossover trial compared paleo with a standard diabetes diet for three months each. On paleo, HbA1c was 0.4 percentage points lower, weight 3 kg lower and waist 4 cm smaller (Jönsson et al., 2009). Only 13 people took part, so treat it as a promising signal, not proof. Our paleo diet for type 2 diabetes guide covers that research in more depth.
Why might paleo work in the short run? The simplest explanation is what it removes. Cutting grains, sugar, sweets and packaged snacks takes out a large share of the calorie-dense foods most people overeat. In a four-week Australian trial, the paleo group ate fewer discretionary “junk” items per day than the group following national guidelines (Genoni et al., 2016).
Other upsides are practical rather than measured:
- Simple rules. “Meat, fish, eggs, vegetables, fruit, nuts” is easy to remember at the store.
- More vegetables and fruit for most people who start from a typical Western diet.
- More protein, which tends to help with fullness. If you want numbers for your body, the TDEE and macro calculator gives a starting target.
For a fuller rundown of the diet’s rules, start with what the paleo diet is.
What are 5 negatives of the paleo diet?
The five negatives with the best evidence are cost, digestive upset, missing nutrients, less fiber variety for your gut, and results that fade. Each one is avoidable or manageable, but only if you know about it going in.
1. It costs more
Fresh meat, fish and produce cost more per calorie than grains, beans and dairy. In the Genoni trial, 69% of the paleo group said their groceries cost more, compared with 6% of the guideline group (Genoni et al., 2016). Harvard’s diet review lists “higher cost” among paleo’s potential pitfalls for the same reason (Harvard T.H. Chan School of Public Health).
How much more depends on what you buy. Ground beef, eggs, frozen vegetables and bananas keep a paleo week affordable; grass-fed steak and wild salmon every night do not. Our paleo diet cost breakdown prices a full budget week against the USDA food plans.
2. Your gut may protest at first
In the same four-week trial, 23% of the paleo group reported diarrhea, versus none in the comparison group (Genoni et al., 2016). A sudden jump in fat, raw vegetables and nuts is a likely culprit, though the study didn’t test causes.
Some people also feel tired, headachy or foggy in the first week or two, often called “paleo flu.” That’s usually the result of a sharp drop in carbohydrates and sodium. Our paleo flu guide explains the sodium math and how long it tends to last.
3. Calcium, vitamin D and iodine can run low
Dropping dairy and grains removes the foods that supply much of the calcium and fortified vitamin D in a typical diet. Harvard notes that meeting calcium needs without dairy would take “five or more servings” a day of foods like collard greens or canned bone-in fish (Harvard T.H. Chan School of Public Health).
Iodine is the gap people rarely expect. Strict paleo drops dairy and iodized table salt, two major iodine sources. In a two-year Swedish trial, daily urinary iodine in the paleo group fell from a median of 134 µg to 77 µg after six months, while the comparison group stayed level. The researchers concluded that iodine supplementation “should be considered” on paleo (Manousou et al., 2018).
The fixes are specific foods, not willpower. Our paleo calcium and nutrient gaps guide works through a dairy-free day that reaches 1,054 mg of calcium.
4. Less resistant starch for your gut bacteria
Resistant starch is the type of carbohydrate that escapes digestion and feeds bacteria in your colon. Whole grains and legumes are major sources, and paleo cuts both. An Australian study compared people who had eaten paleo for more than a year with people eating a typical diet. Resistant starch intake was 2.62 g/day in strict followers and 1.26 g/day in partial followers, versus 4.48 g/day in the comparison group (Genoni et al., 2020).
The strict paleo group also had higher blood levels of TMAO (trimethylamine N-oxide), a compound made by gut bacteria from nutrients in red meat and eggs that has been linked to heart disease. That study was cross-sectional, so it shows an association, not proof that paleo raises heart risk. It’s still a reason to include starchy plants you can eat on paleo, such as cooled potatoes, green bananas and plantains.
5. The advantage fades, and sticking with it is hard
This is the negative that matters most if you want lasting results. The longest paleo trial followed 70 women with obesity for two years. Both groups lost fat, but the paleo group’s lead shrank over time (Mellberg et al., 2014):
| Time point | Paleo group fat loss | Nordic guideline group fat loss | Difference |
|---|---|---|---|
| 6 months | -6.5 kg | -2.6 kg | 3.9 kg (significant) |
| 24 months | -4.6 kg | -2.9 kg | 1.7 kg (not significant) |
Source: Mellberg et al., European Journal of Clinical Nutrition, 2014.
Worked out, the paleo group regained about 1.9 kg (6.5 minus 4.6) between month 6 and month 24, while the comparison group kept losing slowly. The authors also noted that “adherence to protein intake was poor in the PD group”, meaning people drifted from the prescribed plan. Harvard’s review makes the same point in general terms: the restrictive nature of the diet “may also make it difficult for people to adhere to such a diet in the long run.”
Is the paleo diet healthy long term?
Nobody knows for certain, because no trial has followed paleo eaters for more than two years with hard outcomes like heart attacks or fractures. Harvard lists “Is there potential for nutrient deficiencies, such as calcium and vitamin D, when following this diet for longer than one year” among its unanswered questions (Harvard T.H. Chan School of Public Health).
What you eat inside the rules probably matters more than the label. A paleo week built on fish, poultry, eggs, vegetables, fruit, nuts and olive oil looks very different from one built on bacon and steak. Harvard’s review points out that several studies link a high intake of red meat to a higher risk of death, cardiovascular disease and diabetes. The paleo cholesterol guide shows how two paleo days can produce opposite cholesterol profiles depending on fat choices.
If long-term heart health is your main goal, it’s worth comparing paleo with the Mediterranean pattern, which has far more long-term evidence. See paleo vs Mediterranean for that matchup.
Who do the pros outweigh the cons for?
Use this as a starting decision rule, not a diagnosis:
| Your situation | Likely verdict | Why |
|---|---|---|
| You eat a lot of packaged food and sweets and want a clear reset | Pros likely outweigh cons for a trial period | The short-term metabolic benefits are strongest when paleo replaces processed food |
| You have high triglycerides or a large waist and your doctor agrees | Reasonable to try for 3-6 months with follow-up labs | This is where trial benefits were measured |
| You’re on a tight food budget | Cons may outweigh pros unless you plan around cheap proteins | Cost was the most-reported drawback |
| You have or are at risk of osteoporosis | Talk to your doctor first | Calcium and vitamin D gaps are the main long-term unknown |
| You have thyroid disease, are pregnant or breastfeeding | Get medical input before cutting dairy and iodized salt | Iodine needs are higher and the iodine drop is documented |
| You have kidney disease or a history of disordered eating | Don’t start without your care team | Higher protein and strict food rules can be a poor fit |
How can you keep the pros and reduce the cons?
Most of paleo’s downsides come from what drops out of the diet, so the fixes are about adding things back deliberately:
- Keep iodine in. Use iodized salt for cooking unless your doctor says otherwise, and eat seafood a couple of times a week. The Manousou trial authors specifically flagged table salt as one of the iodine sources paleo removes.
- Plan calcium daily. Canned sardines or salmon with bones, cooked greens and almonds do the heavy lifting.
- Feed your gut bacteria. Include cooked-and-cooled potatoes, plantains, green bananas and plenty of vegetables for fiber variety.
- Choose fats on purpose. Lean on olive oil, avocado, nuts and fish; keep butter, bacon and fatty red meat as occasional foods.
- Budget with cheap staples. Eggs, ground meat, chicken thighs, canned fish and frozen vegetables.
- Ease in. Switching one meal at a time for a week or two may help your digestion adjust.
If you’d rather not go strict, a flexible version that keeps some dairy or legumes captures much of the benefit (less processed food, more produce) with fewer gaps. The 9 common paleo mistakes page covers other traps beginners hit.
Frequently asked questions about paleo diet pros and cons
What are 5 negatives of the paleo diet?
The five best-documented negatives are higher grocery costs, early digestive upset such as diarrhea, low calcium, vitamin D and iodine without planning, less resistant starch for gut bacteria, and weight-loss advantages that shrink by two years. In one trial, 69% of paleo eaters reported higher costs and 23% reported diarrhea within four weeks.
Is paleo bad for your kidneys?
The trials haven’t studied kidney outcomes directly; the two-year Mellberg trial only reported that nitrogen excretion didn’t differ between groups. Paleo is usually higher in protein, and people with existing chronic kidney disease are often advised to limit protein. If you have kidney disease, talk to your doctor or a renal dietitian before starting.
Why do some doctors not recommend the paleo diet?
Doctors mostly object to what paleo removes. Whole grains, legumes and dairy have strong evidence behind them, and dropping them raises the risk of low calcium, vitamin D, iodine and fiber intake. Many also worry about high red meat intake. The research supporting paleo is short-term and small, so it’s hard to recommend over diets with decades of data.
Can the paleo diet make you feel worse at first?
Yes, for some people. Tiredness, headaches, irritability and digestive changes in the first one to two weeks are common complaints, usually tied to a sudden drop in carbohydrates and sodium and a jump in fat and fiber. Easing in gradually and keeping salt and fluids up tends to help. See a doctor if symptoms are severe or last more than a few weeks.
Is the paleo diet worth it for weight loss?
It can help you lose weight in the first six months, mainly because it cuts processed, calorie-dense foods. Over two years, the one long trial found paleo’s fat-loss advantage over a standard healthy diet was no longer statistically significant. Whether it’s worth it depends on whether you can keep eating that way.
Is paleo healthier than a normal diet?
Healthier than a typical Western diet heavy in processed food, probably, at least for short-term metabolic markers. Healthier than a well-planned guideline diet or the Mediterranean diet over the long run is unproven. The trials that found paleo ahead compared it with guideline-based diets for six months or less.
Your next step: decide on a trial period, then check your numbers
If the pros fit your situation, treat paleo as a time-limited experiment. Pick a start date, plan calcium and iodine from day one, and ask your doctor about baseline blood work so you can compare triglycerides, cholesterol and blood sugar after three to six months. If the cons are deal-breakers, you can still borrow paleo’s best habit, cooking more whole foods, without the strict rules. For the full rulebook and food lists, head back to the paleo diet guide.
Consider this general nutrition reading, not a replacement for advice from your doctor or a registered dietitian. Talk to your doctor before making major changes to your diet, especially if you have a medical condition or take medication.
Research cited in this guide
- Manheimer EW et al. Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr, 2015 – PubMed
- Mellberg C et al. Long-term effects of a Palaeolithic-type diet in obese postmenopausal women: a 2-year randomized trial. Eur J Clin Nutr, 2014 – PubMed
- Genoni A et al. Compliance, palatability and feasibility of Paleolithic and Australian Guide to Healthy Eating diets in healthy women. Nutrients, 2016 – PubMed
- Genoni A et al. Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations. Eur J Nutr, 2020 – PubMed
- Manousou S et al. A Paleolithic-type diet results in iodine deficiency: a 2-year randomized trial in postmenopausal obese women. Eur J Clin Nutr, 2018 – PubMed
- Jönsson T et al. Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes. Cardiovasc Diabetol, 2009 – PubMed
- Diet Review: Paleo Diet for Weight Loss – Harvard T.H. Chan School of Public Health