San Diego, California - A paleo diet is a dietary plan based on foods similar to what might have been eaten during the Paleolithic era, which dates from approximately 2.5 million to 10,000 years ago.

A paleo diet typically includes lean meats, fish, fruits, vegetables, nuts and seeds — foods that in the past could be obtained by hunting and gathering. A paleo diet limits foods that became common when farming emerged about 10,000 years ago. These foods include dairy products, legumes and grains.

Other names for a paleo diet include Paleolithic diet, Stone Age diet, hunter-gatherer diet and caveman diet.

Purpose

The aim of a paleo diet is to return to a way of eating that's more like what early humans ate. The belief is that the human body is better suited to that type of diet than to the modern diet that emerged with farming.

Farming changed what people ate and established dairy, grains and legumes as additional staples in the human diet. This relatively late and rapid change in diet, according to the hypothesis, outpaced the body's ability to adapt. This mismatch is believed to be a contributing factor to the prevalence of obesity, diabetes and heart disease today.

Why you might follow a paleo diet

You might choose to follow a paleo diet because you:

  • Want to lose weight or maintain a healthy weight
  • Want help planning meals

Details of a paleo diet

Recommendations vary among commercial paleo diets, and some diet plans have stricter guidelines than others. In general, paleo diets follow these guidelines.

What to eat

  • Fruits
  • Vegetables
  • Nuts and seeds
  • Lean meats, especially grass-fed animals or wild game
  • Fish, especially those rich in omega-3 fatty acids, such as salmon, mackerel and albacore tuna
  • Oils from fruits and nuts, such as olive oil or walnut oil

What to avoid

  • Grains, such as wheat, oats and barley
  • Legumes, such as beans, lentils, peanuts and peas
  • Dairy products
  • Refined sugar
  • Salt
  • Potatoes
  • Highly processed foods in general

A typical day's menu

Here's a look at what you might eat during a typical day following a paleo diet:

  • Breakfast. Broiled salmon and cantaloupe.
  • Lunch. Broiled lean pork loin and salad (romaine, carrot, cucumber, tomatoes, walnuts and lemon juice dressing).
  • Dinner. Lean beef sirloin tip roast, steamed broccoli, salad (mixed greens, tomatoes, avocado, onions, almonds and lemon juice dressing) and strawberries for dessert.
  • Snacks. An orange, carrot sticks or celery sticks.

The diet also emphasizes drinking water and being physically active every day.

Results

There is little clinical research on the benefits of paleo diets. A few clinical trials lasting 12 weeks or less have been conducted with small groups of participants.

These trials suggest that a paleo diet may provide some moderate benefits when compared with diets of fruits, vegetables, lean meats, whole grains, legumes and low-fat dairy products. These moderate benefits may include:

  • More weight loss
  • Improved glucose tolerance
  • Better blood pressure control
  • Better appetite management

However, longer trials with large groups of people randomly assigned to different diets are needed to understand the long-term, overall health benefits and possible risks of a paleo diet.

Questions about paleo diets

Concerns or questions about the paleo diet include both food selection and the underlying hypothesis.

Dietary concerns

A paleo diet is rich in vegetables, fruits and nuts — all elements of a healthy diet.

The primary difference between the paleo diet and other healthy diets is the absence of whole grains and legumes, which are considered good sources of fiber, vitamins and other nutrients. Also absent for the diet are dairy products, which are good sources of protein and calcium.

These foods not only are considered healthy but also are generally more affordable and accessible than such foods as wild game, grass-fed animals and nuts. For some people, a paleo diet may be too expensive.

Questions about the paleo diet hypothesis

Researchers have argued that the underlying hypothesis of the paleo diet may oversimplify the story of how humans adapted to changes in diet. Arguments for a more complex understanding of the evolution of human nutritional needs include the following:

  • Variations in diet based on geography, climate and food availability — not only the transition to farming — would also have shaped the evolution of nutritional needs.
  • Archeological research has demonstrated that early human diets may have included wild grains as much as 30,000 years ago — well before the introduction of farming.
  • Genetic research has shown that notable evolutionary changes continued after the Paleolithic era, including diet-related changes, such as an increase in the number of genes related to the breakdown of dietary starches.

The bottom line

A paleo diet may help you lose weight or maintain your weight. It may also have other beneficial health effects. However, there are no long-term clinical studies about the benefits and potential risks of the diet.

You might be able to achieve the same health benefits by getting enough exercise and eating a balanced, healthy diet with a lot of fruits and vegetables.