What is the Paleo Diet?

What is the Paleo Diet?


  • The Paleo diet attempts to model the foods that may have been commonly eaten by humans during the Paleolithic erameat, fish, fruits, vegetables, nuts and seeds.
  • Some research has demonstrated a beneficial effect on body weight and risk factors for type 2 diabetes and cardiovascular disease, though these studies were small and limited in duration.
  • Following a Paleo diet may make it hard to get enough fiber, calcium and other important nutrients. It also poses challenges when it comes to cost, time and convenience.

Basics of the Paleo Diet

The Paleo diet attempts to model what would have been eaten by humans during the Paleolithic era, also known as the prehistoric stone age of human development. This diet includes meats, fish, fruits, vegetables, nuts and seedsfoods that presumably would have been obtained through hunting and gathering. It omits legumes, grains, dairy, refined sugar, lowcalorie sweeteners and “processed” foods.

Paleo proponents argue that the technological changes that came about with farming and other more advanced methods of food productionlike the addition of grains, dairy and legumes to the dietoutpaced our body’s ability to adapt to this new way of eating. This incompatibility, they attest, has contributed to many diet-related diseases we see today.

This hypothesis has some scientific flaws. For example, recent research from the Proceedings of the National Academy of Sciences demonstrates that ancient humans may have begun eating grasses and cereals before the Paleolithic era began, so the idea that no grains were eaten in that time period is most likely an exaggeration. Additional research shows that beans and legumes were eaten in the Paleolithic era as well.

Regardless of whether the idea behind this style of eating is true, the Paleo diet has been adopted by many people seeking to lose weight and improve their health. But what does the research say?

The Paleo Diet and your health

Body Weight

A meta-analysis of 11 randomized controlled studies examined the relationship between adopting a Paleo diet and changes in anthropometric markers like weight, body mass index and waist circumference. Following a Paleo diet was related to statistically significant weight loss (about 3.5 kilograms (kg), or 7.7 pounds), BMI decrease (1.09 kg/meters2) and weight circumference reduction (2.46 centimeters) as compared to diets based on standard dietary recommendations for adults. However, authors noted that more randomized clinical studies with larger populations and duration are necessary to prove the health benefits associated with following the Paleo diet.

Cardiovascular Disease

There is some evidence supporting the beneficial effects of a Paleo diet on cardiovascular disease risk factors. A meta-analysis of eight studies found that a Paleo diet reduced body weight, waist circumference, body fat percentage, blood pressure and total cholesterol (lowered LDL and raised HDL). Though the meta-analysis found positive effects stemming from the Paleo diet, authors also noted that the evidence is not conclusive and more well-designed trials are needed.

Blood Sugar and Type 2 Diabetes

Since the Paleo diet limits carbohydrates, dairy, legumes and refined sugar, it’s no surprise that it has demonstrated reductions in blood sugar and markers of blood glucose control in a few randomized controlled trials. These studies were short and had small sample sizes, so it’s unknown if following a Paleo diet over a long period of time would continue to show positive results. Nevertheless, one study showed that people on Paleo had lower hemoglobin A1C (a marker of blood glucose status) levels as compared to when they were not on Paleo. Another more recent systematic review and meta-analysis found that following a Paleo diet resulted in lower fasting blood sugar as compared with a control diet that did not exclude grains, legumes or dairy.

Overall, studies done exclusively on the Paleo diet’s effects on chronic diseases and body weight are small and limited in duration, though some have demonstrated potential positive effects.


The beneficial health effects of the Paleo diet likely stem from its focus on eating fresh, whole foods and drastically reducing intake of refined grains, added sugars and heavily processed foods. Essentially, following a Paleo diet makes people pay more attention to what they eat, cut out foods with limited nutritional value, and eat more nutrient-dense foods.

However, there are a few limitations to the Paleo diet. For many people, this diet will be too restrictive with its advice on grains, legumes, dairy, refined sugars and low-calorie sweeteners. Plus, avoiding grains, dairy and legumes may limit the amount of fiber, calcium and other nutrients eaten each day. And that’s not to speak of other challenges to following the Paleo dietnamely time, convenience and cost. Time and energy are required to prepare meals that fit into the Paleo diet’s parameters. Though some restaurants and food companies are adapting to this trend, those following this diet may have trouble finding meals that fit while eating away from home. Adopting the Paleo diet could result in spending more money on food if people opt for more fresh produce, meats and fish than usual. At the same time, though, spending more money on these foods could be balanced out by the savings from not buying Paleo-unfriendly foods.

While the Paleo diet emphasizes many healthy foods like fruits, vegetables, lean meats, fish, nuts and seeds, it unnecessarily limits grains, legumes, dairy and other foods that can be incorporated into an overall healthy eating pattern. The Paleo diet may work for some, but we recommend a more balanced approach to healthy eating that allows all types of foods, doesn’t eliminate entire food groups and fits within your budget, schedule and taste preferences.

This blog post includes contributions from Ali Webster, PhD, RD.